Publish

- @now/build-utils@0.5.6
 - @now/go@0.5.1
 - @now/lambda@0.5.4
 - @now/layer-node@0.0.2
 - @now/layer-npm@0.0.2
 - @now/layer-yarn@0.0.2
 - @now/next@0.4.1
 - @now/node-bridge@1.1.4
 - @now/node-server@0.7.4
 - @now/node@0.7.4
 - @now/optipng@0.6.2
 - @now/php-bridge@0.5.3
 - @now/php@0.5.5
 - @now/python@0.2.5
 - @now/rust@0.2.5
 - @now/static-build@0.5.8
 - @now/wordpress@0.5.3

.circleci/config.yml

@@ -29,14 +29,8 @@ jobs:
       - run:
           name: Tests and Coverage
           command: yarn test-coverage
-      - run:
-          name: Potentially save npm token
-          command: "([[ ! -z $NPM_TOKEN ]] && echo \"//registry.npmjs.org/:_authToken=$NPM_TOKEN\" >> ~/.npmrc) || echo \"Did not write npm token\""
-      - run:
-          name: Potentially publish releases to npm
-          command: ./.circleci/publish.sh
 workflows:
   version: 2
-  build-and-deploy:
+  build-and-test:
     jobs:
       - build

.circleci/publish.sh

@@ -1,6 +1,13 @@
 #!/bin/bash
 set -euo pipefail
 
+if [ -z "$NPM_TOKEN" ]; then
+  echo "NPM_TOKEN not found. Did you forget to assign the GitHub Action secret?"
+  exit 1
+fi
+
+echo "//registry.npmjs.org/:_authToken=$NPM_TOKEN" >> ~/.npmrc
+
 if [ ! -e ~/.npmrc ]; then
   echo "~/.npmrc file does not exist, skipping publish"
   exit 0

.editorconfig

@@ -0,0 +1,43 @@
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[{*.json,*.json.example,*.gyp,*.yml,*.yaml,*.workflow}]
+indent_style = space
+indent_size = 2
+
+[{*.py,*.asm}]
+indent_style = space
+
+[*.py]
+indent_size = 4
+
+[*.asm]
+indent_size = 8
+
+[*.md]
+trim_trailing_whitespace = false
+indent_style = space
+indent_size = 2
+
+# Ideal settings - some plugins might support these
+[*.js,*.jsx,*.ts,*.tsx]
+quote_type = single
+indent_style = space
+indent_size = 2
+
+[{*.c,*.cc,*.h,*.hh,*.cpp,*.hpp,*.m,*.mm,*.mpp,*.java,*.go,*.rs,*.php,*.ng,*.d,*.cs,*.swift}]
+indent_style = tab
+indent_size = 4
+tab_width = 4
+
+[{*.c,*.cc,*.h,*.hh,*.cpp,*.hpp,*.m,*.mm,*.mpp,*.js,*.java,*.go,*.rs,*.php,*.ng,*.jsx,*.ts,*.tsx,*.d,*.cs,*.swift}]
+curly_bracket_next_line = false
+spaces_around_operators = true
+spaces_around_brackets = outside
+# close enough to 1TB
+indent_brace_style = K&R

.eslintignore

@@ -3,8 +3,15 @@
 /**/node_modules/*
 /packages/now-go/go/*
 /packages/now-build-utils/dist/*
+/packages/now-build-utils/src/*.js
+/packages/now-build-utils/src/fs/*.js
 /packages/now-node/dist/*
+/packages/now-layer-node/dist/*
+/packages/now-layer-npm/dist/*
+/packages/now-layer-yarn/dist/*
 /packages/now-next/dist/*
 /packages/now-node-bridge/*
-/packages/now-python/*
+/packages/now-python/dist/*
 /packages/now-optipng/dist/*
+/packages/now-go/*
+/packages/now-rust/dist/*

.github/CODEOWNERS

@@ -0,0 +1,9 @@
+# Documentation
+# https://help.github.com/en/articles/about-code-owners
+
+*                       @styfle
+/packages/now-node      @styfle @tootallnate
+/packages/now-next      @timer  @dav-is
+/packages/now-go        @styfle @sophearak
+/packages/now-python    @styfle @sophearak
+/packages/now-rust      @styfle @mike-engel @anmonteiro

.github/main.workflow

@@ -0,0 +1,76 @@
+workflow "Canary publish" {
+  on = "push"
+  resolves = ["3. Canary yarn run publish"]
+}
+
+action "0. Canary filter" {
+  uses = "actions/bin/filter@3c0b4f0e63ea54ea5df2914b4fabf383368cd0da"
+  args = "branch canary"
+}
+
+action "0. Canary PR not deleted" {
+  uses = "actions/bin/filter@3c0b4f0e63ea54ea5df2914b4fabf383368cd0da"
+  needs = ["0. Canary filter"]
+  args = "not deleted"
+}
+
+action "1. Canary yarn install" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["0. Canary PR not deleted"]
+  runs = "yarn"
+  args = "install"
+}
+
+action "2. Canary yarn run build" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["1. Canary yarn install"]
+  runs = "yarn"
+  args = "run build"
+}
+
+action "3. Canary yarn run publish" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["2. Canary yarn run build"]
+  runs = "yarn"
+  args = "run publish-from-github"
+  secrets = ["NPM_TOKEN"]
+}
+
+
+workflow "Master publish" {
+  on = "push"
+  resolves = ["3. Master yarn run publish"]
+}
+
+action "0. Master filter" {
+  uses = "actions/bin/filter@3c0b4f0e63ea54ea5df2914b4fabf383368cd0da"
+  args = "branch master"
+}
+
+action "0. Master PR not deleted" {
+  uses = "actions/bin/filter@3c0b4f0e63ea54ea5df2914b4fabf383368cd0da"
+  needs = ["0. Master filter"]
+  args = "not deleted"
+}
+
+action "1. Master yarn install" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["0. Master PR not deleted"]
+  runs = "yarn"
+  args = "install"
+}
+
+action "2. Master yarn run build" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["1. Master yarn install"]
+  runs = "yarn"
+  args = "run build"
+}
+
+action "3. Master yarn run publish" {
+  uses = "actions/npm@59b64a598378f31e49cb76f27d6f3312b582f680"
+  needs = ["2. Master yarn run build"]
+  runs = "yarn"
+  args = "run publish-from-github"
+  secrets = ["NPM_TOKEN"]
+}

.gitignore

@@ -2,3 +2,5 @@ node_modules
 tmp
 target/
 .next
+coverage
+*.tgz

.prettierrc.json

@@ -1,4 +0,0 @@
-{
-  "singleQuote": true,
-  "trailingComma": "es5"
-}

.yarnrc

@@ -0,0 +1 @@
+save-prefix ""

CODE_OF_CONDUCT.md

@@ -0,0 +1,74 @@
+## Code of Conduct
+
+### Our Pledge
+
+In the interest of fostering an open and welcoming environment, we as
+contributors and maintainers pledge to making participation in our project and
+our community a harassment-free experience for everyone, regardless of age, body
+size, disability, ethnicity, gender identity and expression, level of experience,
+nationality, personal appearance, race, religion, or sexual identity and
+orientation.
+
+### Our Standards
+
+Examples of behavior that contributes to creating a positive environment
+include:
+
+- Using welcoming and inclusive language
+- Being respectful of differing viewpoints and experiences
+- Gracefully accepting constructive criticism
+- Focusing on what is best for the community
+- Showing empathy towards other community members
+
+Examples of unacceptable behavior by participants include:
+
+- The use of sexualized language or imagery and unwelcome sexual attention or
+  advances
+- Trolling, insulting/derogatory comments, and personal or political attacks
+- Public or private harassment
+- Publishing others' private information, such as a physical or electronic
+  address, without explicit permission
+- Other conduct which could reasonably be considered inappropriate in a
+  professional setting
+
+### Our Responsibilities
+
+Project maintainers are responsible for clarifying the standards of acceptable
+behavior and are expected to take appropriate and fair corrective action in
+response to any instances of unacceptable behavior.
+
+Project maintainers have the right and responsibility to remove, edit, or
+reject comments, commits, code, wiki edits, issues, and other contributions
+that are not aligned to this Code of Conduct, or to ban temporarily or
+permanently any contributor for other behaviors that they deem inappropriate,
+threatening, offensive, or harmful.
+
+### Scope
+
+This Code of Conduct applies both within project spaces and in public spaces
+when an individual is representing the project or its community. Examples of
+representing a project or community include using an official project e-mail
+address, posting via an official social media account, or acting as an appointed
+representative at an online or offline event. Representation of a project may be
+further defined and clarified by project maintainers.
+
+### Enforcement
+
+Instances of abusive, harassing, or otherwise unacceptable behavior may be
+reported by contacting the project team at [abuse@zeit.co](mailto:abuse@zeit.co). All
+complaints will be reviewed and investigated and will result in a response that
+is deemed necessary and appropriate to the circumstances. The project team is
+obligated to maintain confidentiality with regard to the reporter of an incident.
+Further details of specific enforcement policies may be posted separately.
+
+Project maintainers who do not follow or enforce the Code of Conduct in good
+faith may face temporary or permanent repercussions as determined by other
+members of the project's leadership.
+
+### Attribution
+
+This Code of Conduct is adapted from the [Contributor Covenant][homepage], version 1.4,
+available at [http://contributor-covenant.org/version/1/4][version]
+
+[homepage]: http://contributor-covenant.org
+[version]: http://contributor-covenant.org/version/1/4/

README.md

@@ -1,8 +1,11 @@
 # now-builders
 
-This is the full list of official Builders provided by the ZEIT team.
+This is a monorepo containing the [Official Builders](https://zeit.co/docs/v2/deployments/builders/overview) provided by the ZEIT team.
 
-More details here: https://zeit.co/docs/v2/deployments/builders/overview/
+There are two branches:
+
+- canary - published to npm as `canary` dist-tag, eg `@now/node@canary`
+- master - published to npm as `latest` dist-tag, eg `@now/node@latest`
 
 ### Publishing to npm
 
@@ -20,8 +23,8 @@ For the canary channel use:
 yarn publish-canary
 ```
 
-CircleCI will take care of publishing the updated packages to npm from there.
+GitHub Actions will take care of publishing the updated packages to npm from there.
 
-If for some reason CircleCI fails to publish the npm package, you may do so
+If for some reason GitHub Actions fails to publish the npm package, you may do so
 manually by running `npm publish` from the package directory. Make sure to
-include the `--tag canary` parameter if you are publishing a canary release!
+use `npm publish --tag canary` if you are publishing a canary release!

errors/now-next-legacy-mode.md

@@ -29,7 +29,6 @@ Serverless:
 - No runtime dependencies, meaning smaller lambda functions
 - Optimized for fast [cold start](https://zeit.co/blog/serverless-ssr#cold-start)
 
-
 #### Possible Ways to Fix It
 
 In order to create the smallest possible lambdas Next.js has to be configured to build for the `serverless` target.
@@ -46,7 +45,7 @@ npm install next --save
 {
   "scripts": {
     "now-build": "next build"
-  },
+  }
 }
 ```
 
@@ -54,9 +53,9 @@ npm install next --save
 
 ```js
 module.exports = {
-  target: 'serverless'
+  target: 'serverless',
   // Other options are still valid
-}
+};
 ```
 
 4. Optionally make sure the `"src"` in `"builds"` points to your application `package.json`

errors/now-next-no-serverless-pages-built.md

@@ -20,7 +20,7 @@ npm install next --save
 {
   "scripts": {
     "now-build": "next build"
-  },
+  }
 }
 ```
 
@@ -28,9 +28,9 @@ npm install next --save
 
 ```js
 module.exports = {
-  target: 'serverless'
+  target: 'serverless',
   // Other options
-}
+};
 ```
 
 4. Remove `distDir` from `next.config.js` as `@now/next` can't parse this file and expects your build output at `/.next`

errors/now-static-build-failed-to-detect-a-server.md

@@ -0,0 +1,38 @@
+# `@now/static-build` Failed to detect a server running
+
+#### Why This Warning Occurred
+
+When running `now dev`, the `@now/static-build` builder proxies relevant HTTP
+requests to the server that is created by the `now-dev` script in the
+`package.json` file.
+
+In order for `now dev` to know which port the server is running on, the builder
+is provided a `$PORT` environment variable that the server _must_ bind to. The
+error "Failed to detect a server running on port" is printed if the builder fails
+to detect a server listening on that specific port within five minutes.
+
+#### Possible Ways to Fix It
+
+Please ensure that your `now-dev` script binds the spawned development server on
+the provided `$PORT` that the builder expects the server to bind to.
+
+For example, if you are using Gatsby, your `now-dev` script must use the `-p`
+(port) option to bind to the `$PORT` specified from the builder:
+
+```
+{
+  ...
+  "scripts": {
+    ...
+    "now-dev": "gatsby develop -p $PORT"
+  }
+}
+```
+
+Consult your static builder program's `--help` or documentation to figure out what
+the command line flag to bind to a specific port is (in many cases, it is one of:
+`-p` / `-P` / `--port`).
+
+### Useful Links
+
+- [`@now/static-build` Local Development Documentation](https://zeit.co/docs/v2/deployments/official-builders/static-build-now-static-build#local-development)

jest.config.js

@@ -1,5 +1,37 @@
+const childProcess = require('child_process');
+const path = require('path');
+
+const command = 'git diff HEAD~1 --name-only';
+const diff = childProcess.execSync(command).toString();
+
+const changed = diff
+  .split('\n')
+  .filter(item => Boolean(item) && item.includes('packages/'))
+  .map(item => path.relative('packages', item).split('/')[0]);
+
+const matches = [];
+
+if (changed.length > 0) {
+  console.log('The following packages have changed:');
+
+  changed.map((item) => {
+    matches.push(item);
+    console.log(item);
+
+    return null;
+  });
+} else {
+  matches.push('now-node');
+  console.log(`No packages changed, defaulting to ${matches[0]}`);
+}
+
+const testMatch = Array.from(new Set(matches)).map(
+  item => `**/${item}/**/?(*.)+(spec|test).[jt]s?(x)`,
+);
+
 module.exports = {
   testEnvironment: 'node',
+  testMatch,
   collectCoverageFrom: [
     'packages/(!test)/**/*.{js,jsx}',
     '!**/node_modules/**',

lerna.json

@@ -1,9 +1,7 @@
 {
   "npmClient": "yarn",
   "useWorkspaces": true,
-  "packages": [
-    "packages/*"
-  ],
+  "packages": ["packages/*"],
   "command": {
     "publish": {
       "npmClient": "npm",

package.json

@@ -12,8 +12,9 @@
   "scripts": {
     "lerna": "lerna",
     "bootstrap": "lerna bootstrap",
-    "publish-stable": "lerna version",
-    "publish-canary": "lerna version prerelease --preid canary",
+    "publish-stable": "git checkout master && git pull && lerna version",
+    "publish-canary": "git checkout canary && git pull && lerna version prerelease --preid canary",
+    "publish-from-github": "./.circleci/publish.sh",
     "build": "./.circleci/build.sh",
     "lint": "eslint .",
     "codecov": "codecov",
@@ -51,6 +52,10 @@
     "lint-staged": "^8.0.4",
     "node-fetch": "^2.3.0",
     "pre-commit": "^1.2.2",
-    "prettier": "^1.15.2"
+    "prettier": "1.17.1"
+  },
+  "prettier": {
+    "singleQuote": true,
+    "trailingComma": "es5"
   }
 }

packages/now-bash/index.js

@@ -1,10 +1,13 @@
 const execa = require('execa');
 const { join } = require('path');
 const snakeCase = require('snake-case');
-const glob = require('@now/build-utils/fs/glob'); // eslint-disable-line import/no-extraneous-dependencies
-const download = require('@now/build-utils/fs/download'); // eslint-disable-line import/no-extraneous-dependencies
-const { createLambda } = require('@now/build-utils/lambda'); // eslint-disable-line import/no-extraneous-dependencies
-const getWritableDirectory = require('@now/build-utils/fs/get-writable-directory'); // eslint-disable-line import/no-extraneous-dependencies
+const {
+  glob,
+  download,
+  createLambda,
+  getWriteableDirectory,
+  shouldServe,
+} = require('@now/build-utils'); // eslint-disable-line import/no-extraneous-dependencies
 
 exports.config = {
   maxLambdaSize: '10mb',
@@ -15,7 +18,7 @@ exports.analyze = ({ files, entrypoint }) => files[entrypoint].digest;
 exports.build = async ({
   workPath, files, entrypoint, config,
 }) => {
-  const srcDir = await getWritableDirectory();
+  const srcDir = await getWriteableDirectory();
 
   console.log('downloading files...');
   await download(files, srcDir);
@@ -55,3 +58,5 @@ exports.build = async ({
     [entrypoint]: lambda,
   };
 };
+
+exports.shouldServe = shouldServe;

packages/now-bash/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/bash",
-  "version": "0.2.0",
+  "version": "0.2.3",
   "description": "Now 2.0 builder for HTTP endpoints written in Bash",
   "main": "index.js",
   "author": "Nathan Rajlich <nate@zeit.co>",

packages/now-build-utils/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/build-utils",
-  "version": "0.5.0",
+  "version": "0.5.6",
   "license": "MIT",
   "main": "./dist/index.js",
   "types": "./dist/index.d.js",
@@ -10,8 +10,10 @@
     "directory": "packages/now-build-utils"
   },
   "dependencies": {
+    "@types/cross-spawn": "6.0.0",
     "async-retry": "1.2.3",
     "async-sema": "2.1.4",
+    "cross-spawn": "6.0.5",
     "end-of-stream": "1.4.1",
     "fs-extra": "7.0.0",
     "glob": "7.1.3",

packages/now-build-utils/src/file-fs-ref.ts

@@ -31,7 +31,10 @@ class FileFsRef implements File {
     this.fsPath = fsPath;
   }
 
-  static async fromFsPath({ mode, fsPath }: FileFsRefOptions): Promise<FileFsRef> {
+  static async fromFsPath({
+    mode,
+    fsPath,
+  }: FileFsRefOptions): Promise<FileFsRef> {
     let m = mode;
     if (!m) {
       const stat = await fs.lstat(fsPath);
@@ -40,7 +43,11 @@ class FileFsRef implements File {
     return new FileFsRef({ mode: m, fsPath });
   }
 
-  static async fromStream({ mode = 0o100644, stream, fsPath }: FromStreamOptions): Promise<FileFsRef> {
+  static async fromStream({
+    mode = 0o100644,
+    stream,
+    fsPath,
+  }: FromStreamOptions): Promise<FileFsRef> {
     assert(typeof mode === 'number');
     assert(typeof stream.pipe === 'function'); // is-stream
     assert(typeof fsPath === 'string');
@@ -48,7 +55,7 @@ class FileFsRef implements File {
 
     await new Promise<void>((resolve, reject) => {
       const dest = fs.createWriteStream(fsPath, {
-        mode: mode & 0o777
+        mode: mode & 0o777,
       });
       stream.pipe(dest);
       stream.on('error', reject);
@@ -72,15 +79,15 @@ class FileFsRef implements File {
     let flag = false;
 
     // eslint-disable-next-line consistent-return
-    return multiStream((cb) => {
+    return multiStream(cb => {
       if (flag) return cb(null, null);
       flag = true;
 
       this.toStreamAsync()
-        .then((stream) => {
+        .then(stream => {
           cb(null, stream);
         })
-        .catch((error) => {
+        .catch(error => {
           cb(error, null);
         });
     });

packages/now-build-utils/src/file-ref.ts

@@ -8,7 +8,6 @@ import { File } from './types';
 interface FileRefOptions {
   mode?: number;
   digest: string;
-  mutable?: boolean;
 }
 
 const semaToDownloadFromS3 = new Sema(5);
@@ -26,26 +25,29 @@ export default class FileRef implements File {
   public type: 'FileRef';
   public mode: number;
   public digest: string;
-  public mutable: boolean;
 
-  constructor({ mode = 0o100644, digest, mutable = false }: FileRefOptions) {
+  constructor({ mode = 0o100644, digest }: FileRefOptions) {
     assert(typeof mode === 'number');
     assert(typeof digest === 'string');
-    assert(typeof mutable === 'boolean');
     this.type = 'FileRef';
     this.mode = mode;
     this.digest = digest;
-    this.mutable = mutable;
   }
 
   async toStreamAsync(): Promise<NodeJS.ReadableStream> {
     let url = '';
     // sha:24be087eef9fac01d61b30a725c1a10d7b45a256
-    const digestParts = this.digest.split(':');
-    if (digestParts[0] === 'sha') {
-      url = this.mutable
-        ? `https://s3.amazonaws.com/now-files/${digestParts[1]}`
-        : `https://dmmcy0pwk6bqi.cloudfront.net/${digestParts[1]}`;
+    const [digestType, digestHash] = this.digest.split(':');
+    if (digestType === 'sha') {
+      // This CloudFront URL edge caches the `now-files` S3 bucket to prevent
+      // overloading it
+      // `https://now-files.s3.amazonaws.com/${digestHash}`
+      url = `https://dmmcy0pwk6bqi.cloudfront.net/${digestHash}`;
+    } else if (digestType === 'sha+ephemeral') {
+      // This URL is currently only used for cache files that constantly
+      // change. We shouldn't cache it on CloudFront because it'd always be a
+      // MISS.
+      url = `https://now-ephemeral-files.s3.amazonaws.com/${digestHash}`;
     } else {
       throw new Error('Expected digest to be sha');
     }
@@ -58,14 +60,14 @@ export default class FileRef implements File {
           const resp = await fetch(url);
           if (!resp.ok) {
             const error = new BailableError(
-              `download: ${resp.status} ${resp.statusText} for ${url}`,
+              `download: ${resp.status} ${resp.statusText} for ${url}`
             );
             if (resp.status === 403) error.bail = true;
             throw error;
           }
           return resp.body;
         },
-        { factor: 1, retries: 3 },
+        { factor: 1, retries: 3 }
       );
     } finally {
       // console.timeEnd(`downloading ${url}`);
@@ -77,15 +79,15 @@ export default class FileRef implements File {
     let flag = false;
 
     // eslint-disable-next-line consistent-return
-    return multiStream((cb) => {
+    return multiStream(cb => {
       if (flag) return cb(null, null);
       flag = true;
 
       this.toStreamAsync()
-        .then((stream) => {
+        .then(stream => {
           cb(null, stream);
         })
-        .catch((error) => {
+        .catch(error => {
           cb(error, null);
         });
     });

packages/now-build-utils/src/fs/download.ts

@@ -4,7 +4,7 @@ import { File, Files, Meta } from '../types';
 import { remove, mkdirp, readlink, symlink } from 'fs-extra';
 
 export interface DownloadedFiles {
-  [filePath: string]: FileFsRef
+  [filePath: string]: FileFsRef;
 }
 
 const S_IFMT = 61440; /* 0170000 type of file */
@@ -17,9 +17,9 @@ export function isSymbolicLink(mode: number): boolean {
 async function downloadFile(file: File, fsPath: string): Promise<FileFsRef> {
   const { mode } = file;
   if (mode && isSymbolicLink(mode) && file.type === 'FileFsRef') {
-    const [ target ] = await Promise.all([
+    const [target] = await Promise.all([
       readlink((file as FileFsRef).fsPath),
-      mkdirp(path.dirname(fsPath))
+      mkdirp(path.dirname(fsPath)),
     ]);
     await symlink(target, fsPath);
     return FileFsRef.fromFsPath({ mode, fsPath });
@@ -34,12 +34,25 @@ async function removeFile(basePath: string, fileMatched: string) {
   await remove(file);
 }
 
-export default async function download(files: Files, basePath: string, meta?: Meta): Promise<DownloadedFiles> {
+export default async function download(
+  files: Files,
+  basePath: string,
+  meta?: Meta
+): Promise<DownloadedFiles> {
+  const { isDev = false, filesChanged = null, filesRemoved = null } =
+    meta || {};
+
+  if (isDev) {
+    // In `now dev`, the `download()` function is a no-op because
+    // the `basePath` matches the `cwd` of the dev server, so the
+    // source files are already available.
+    return files as DownloadedFiles;
+  }
+
   const files2: DownloadedFiles = {};
-  const { filesChanged = null, filesRemoved = null } = meta || {};
 
   await Promise.all(
-    Object.keys(files).map(async (name) => {
+    Object.keys(files).map(async name => {
       // If the file does not exist anymore, remove it.
       if (Array.isArray(filesRemoved) && filesRemoved.includes(name)) {
         await removeFile(basePath, name);
@@ -55,7 +68,7 @@ export default async function download(files: Files, basePath: string, meta?: Me
       const fsPath = path.join(basePath, name);
 
       files2[name] = await downloadFile(file, fsPath);
-    }),
+    })
   );
 
   return files2;

packages/now-build-utils/src/fs/glob.ts

@@ -8,12 +8,16 @@ import FileFsRef from '../file-fs-ref';
 type GlobOptions = vanillaGlob_.IOptions;
 
 interface FsFiles {
-  [filePath: string]: FileFsRef
+  [filePath: string]: FileFsRef;
 }
 
 const vanillaGlob = promisify(vanillaGlob_);
 
-export default async function glob(pattern: string, opts: GlobOptions | string, mountpoint?: string): Promise<FsFiles> {
+export default async function glob(
+  pattern: string,
+  opts: GlobOptions | string,
+  mountpoint?: string
+): Promise<FsFiles> {
   let options: GlobOptions;
   if (typeof opts === 'string') {
     options = { cwd: opts };
@@ -23,7 +27,7 @@ export default async function glob(pattern: string, opts: GlobOptions | string,
 
   if (!options.cwd) {
     throw new Error(
-      'Second argument (basePath) must be specified for names of resulting files',
+      'Second argument (basePath) must be specified for names of resulting files'
     );
   }
 
@@ -41,11 +45,11 @@ export default async function glob(pattern: string, opts: GlobOptions | string,
   const files = await vanillaGlob(pattern, options);
 
   for (const relativePath of files) {
-    const fsPath = path.join(options.cwd!, relativePath);
+    const fsPath = path.join(options.cwd!, relativePath).replace(/\\/g, '/');
     let stat: Stats = options.statCache![fsPath] as Stats;
     assert(
       stat,
-      `statCache does not contain value for ${relativePath} (resolved to ${fsPath})`,
+      `statCache does not contain value for ${relativePath} (resolved to ${fsPath})`
     );
     if (stat.isFile()) {
       const isSymlink = options.symlinks![fsPath];

packages/now-build-utils/src/fs/rename.ts

@@ -7,6 +7,6 @@ export default function rename(files: Files, delegate: Delegate): Files {
       ...newFiles,
       [delegate(name)]: files[name],
     }),
-    {},
+    {}
   );
 }

packages/now-build-utils/src/fs/run-user-scripts.ts

@@ -1,22 +1,28 @@
 import assert from 'assert';
 import fs from 'fs-extra';
 import path from 'path';
-import { spawn, SpawnOptions } from 'child_process';
+import spawn from 'cross-spawn';
+import { SpawnOptions } from 'child_process';
 
-function spawnAsync(command: string, args: string[], cwd: string, opts: SpawnOptions = {}) {
+function spawnAsync(
+  command: string,
+  args: string[],
+  cwd: string,
+  opts: SpawnOptions = {}
+) {
   return new Promise<void>((resolve, reject) => {
-    const stderrLogs: Buffer[] = []
+    const stderrLogs: Buffer[] = [];
     opts = { stdio: 'inherit', cwd, ...opts };
     const child = spawn(command, args, opts);
 
-    if (opts.stdio === 'pipe'){
+    if (opts.stdio === 'pipe') {
       child.stderr.on('data', data => stderrLogs.push(data));
     }
 
     child.on('error', reject);
     child.on('close', (code, signal) => {
       if (code === 0) {
-        return resolve()
+        return resolve();
       }
 
       const errorLogs = stderrLogs.map(line => line.toString()).join('');
@@ -58,13 +64,15 @@ async function scanParentDirs(destPath: string, scriptName?: string) {
     // eslint-disable-next-line no-await-in-loop
     if (await fs.pathExists(packageJsonPath)) {
       // eslint-disable-next-line no-await-in-loop
-      const packageJson = JSON.parse(await fs.readFile(packageJsonPath, 'utf8'));
+      const packageJson = JSON.parse(
+        await fs.readFile(packageJsonPath, 'utf8')
+      );
       hasScript = Boolean(
-        packageJson.scripts && scriptName && packageJson.scripts[scriptName],
+        packageJson.scripts && scriptName && packageJson.scripts[scriptName]
       );
       // eslint-disable-next-line no-await-in-loop
       hasPackageLockJson = await fs.pathExists(
-        path.join(currentDestPath, 'package-lock.json'),
+        path.join(currentDestPath, 'package-lock.json')
       );
       break;
     }
@@ -77,7 +85,10 @@ async function scanParentDirs(destPath: string, scriptName?: string) {
   return { hasScript, hasPackageLockJson };
 }
 
-export async function installDependencies(destPath: string, args: string[] = []) {
+export async function installDependencies(
+  destPath: string,
+  args: string[] = []
+) {
   assert(path.isAbsolute(destPath));
 
   let commandArgs = args;
@@ -91,23 +102,23 @@ export async function installDependencies(destPath: string, args: string[] = [])
       // Node.js version that `@now/node` and `@now/node-server` use
       npm_config_target: '8.10.0',
     },
-    stdio: 'pipe'
+    stdio: 'pipe',
   };
 
   if (hasPackageLockJson) {
     commandArgs = args.filter(a => a !== '--prefer-offline');
     await spawnAsync(
       'npm',
-      ['install'].concat(commandArgs),
+      ['install', '--unsafe-perm'].concat(commandArgs),
       destPath,
       opts as SpawnOptions
     );
   } else {
     await spawnAsync(
       'yarn',
-      ['--cwd', destPath].concat(commandArgs),
+      ['--ignore-engines', '--cwd', destPath].concat(commandArgs),
       destPath,
-      opts as SpawnOptions,
+      opts as SpawnOptions
     );
   }
 }
@@ -120,7 +131,7 @@ export async function runPackageJsonScript(
   assert(path.isAbsolute(destPath));
   const { hasScript, hasPackageLockJson } = await scanParentDirs(
     destPath,
-    scriptName,
+    scriptName
   );
   if (!hasScript) return false;
 
@@ -129,7 +140,12 @@ export async function runPackageJsonScript(
     await spawnAsync('npm', ['run', scriptName], destPath, opts);
   } else {
     console.log(`running "yarn run ${scriptName}"`);
-    await spawnAsync('yarn', ['--cwd', destPath, 'run', scriptName], destPath, opts);
+    await spawnAsync(
+      'yarn',
+      ['--cwd', destPath, 'run', scriptName],
+      destPath,
+      opts
+    );
   }
 
   return true;

packages/now-build-utils/src/fs/stream-to-buffer.ts

@@ -1,12 +1,14 @@
 import eos from 'end-of-stream';
 
-export default function streamToBuffer(stream: NodeJS.ReadableStream): Promise<Buffer> {
+export default function streamToBuffer(
+  stream: NodeJS.ReadableStream
+): Promise<Buffer> {
   return new Promise<Buffer>((resolve, reject) => {
     const buffers: Buffer[] = [];
 
-    stream.on('data', buffers.push.bind(buffers))
+    stream.on('data', buffers.push.bind(buffers));
 
-    eos(stream, (err) => {
+    eos(stream, err => {
       if (err) {
         reject(err);
         return;

packages/now-build-utils/src/index.ts

@@ -1,13 +1,26 @@
 import FileBlob from './file-blob';
 import FileFsRef from './file-fs-ref';
 import FileRef from './file-ref';
-import { File, Files, AnalyzeOptions, BuildOptions, PrepareCacheOptions, ShouldServeOptions, Meta } from './types';
+import {
+  File,
+  Files,
+  AnalyzeOptions,
+  BuildOptions,
+  PrepareCacheOptions,
+  ShouldServeOptions,
+  Meta,
+} from './types';
 import { Lambda, createLambda } from './lambda';
-import download from './fs/download';
-import getWriteableDirectory from './fs/get-writable-directory'
+import download, { DownloadedFiles } from './fs/download';
+import getWriteableDirectory from './fs/get-writable-directory';
 import glob from './fs/glob';
 import rename from './fs/rename';
-import { installDependencies, runPackageJsonScript, runNpmInstall, runShellScript } from './fs/run-user-scripts';
+import {
+  installDependencies,
+  runPackageJsonScript,
+  runNpmInstall,
+  runShellScript,
+} from './fs/run-user-scripts';
 import streamToBuffer from './fs/stream-to-buffer';
 import shouldServe from './should-serve';
 
@@ -21,10 +34,14 @@ export {
   Lambda,
   createLambda,
   download,
+  DownloadedFiles,
   getWriteableDirectory,
   glob,
   rename,
-    installDependencies, runPackageJsonScript, runNpmInstall, runShellScript,
+  installDependencies,
+  runPackageJsonScript,
+  runNpmInstall,
+  runShellScript,
   streamToBuffer,
   AnalyzeOptions,
   BuildOptions,

packages/now-build-utils/src/lambda.ts

@@ -32,9 +32,7 @@ export class Lambda {
   public runtime: string;
   public environment: Environment;
 
-  constructor({
-    zipBuffer, handler, runtime, environment,
-  }: LambdaOptions) {
+  constructor({ zipBuffer, handler, runtime, environment }: LambdaOptions) {
     this.type = 'Lambda';
     this.zipBuffer = zipBuffer;
     this.handler = handler;
@@ -47,7 +45,10 @@ const sema = new Sema(10);
 const mtime = new Date(1540000000000);
 
 export async function createLambda({
-  files, handler, runtime, environment = {},
+  files,
+  handler,
+  runtime,
+  environment = {},
 }: CreateLambdaOptions): Promise<Lambda> {
   assert(typeof files === 'object', '"files" must be an object');
   assert(typeof handler === 'string', '"handler" is not a string');
@@ -97,7 +98,9 @@ export async function createZip(files: Files): Promise<Buffer> {
     }
 
     zipFile.end();
-    streamToBuffer(zipFile.outputStream).then(resolve).catch(reject);
+    streamToBuffer(zipFile.outputStream)
+      .then(resolve)
+      .catch(reject);
   });
 
   return zipBuffer;

packages/now-build-utils/src/should-serve.ts

@@ -5,7 +5,7 @@ import FileFsRef from './file-fs-ref';
 export default function shouldServe({
   entrypoint,
   files,
-  requestPath
+  requestPath,
 }: ShouldServeOptions): boolean {
   requestPath = requestPath.replace(/\/$/, ''); // sanitize trailing '/'
   entrypoint = entrypoint.replace(/\\/, '/'); // windows compatibility
@@ -23,5 +23,5 @@ export default function shouldServe({
 }
 
 function hasProp(obj: { [path: string]: FileFsRef }, key: string): boolean {
-  return Object.hasOwnProperty.call(obj, key)
+  return Object.hasOwnProperty.call(obj, key);
 }

packages/now-build-utils/src/types.ts

@@ -5,6 +5,9 @@ export interface File {
   type: string;
   mode: number;
   toStream: () => NodeJS.ReadableStream;
+  /**
+   * The absolute path to the file in the filesystem
+   */
   fsPath?: string;
 }
 

packages/now-build-utils/test/fixtures/07-cross-install/now.json

@@ -1,9 +1,10 @@
 {
   "version": 2,
-  "builds": [
-    { "src": "api/index.js", "use": "@now/node" }
-  ],
+  "builds": [{ "src": "api/index.js", "use": "@now/node" }],
   "probes": [
-    { "path": "/api/index.js", "mustContain": "cross-cow:RANDOMNESS_PLACEHOLDER" }
+    {
+      "path": "/api/index.js",
+      "mustContain": "cross-cow:RANDOMNESS_PLACEHOLDER"
+    }
   ]
 }

packages/now-build-utils/test/fixtures/15-yarn-ignore-engines/index.js

@@ -0,0 +1,9 @@
+const scheduler = require('@google-cloud/scheduler');
+
+module.exports = (_, res) => {
+  if (scheduler) {
+    res.end('found:RANDOMNESS_PLACEHOLDER');
+  } else {
+    res.end('nope:RANDOMNESS_PLACEHOLDER');
+  }
+};

packages/now-build-utils/test/fixtures/15-yarn-ignore-engines/now.json

@@ -0,0 +1,11 @@
+{
+  "version": 2,
+  "builds": [
+    {
+      "src": "index.js",
+      "use": "@now/node",
+      "config": { "maxLambdaSize": "15mb" }
+    }
+  ],
+  "probes": [{ "path": "/", "mustContain": "found:RANDOMNESS_PLACEHOLDER" }]
+}

packages/now-build-utils/test/fixtures/15-yarn-ignore-engines/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "15-yarn-ignore-engines",
+  "version": "1.0.0",
+  "main": "index.js",
+  "dependencies": {
+    "@google-cloud/scheduler": "0.3.0"
+  }
+}

packages/now-build-utils/tsconfig.json

@@ -15,10 +15,6 @@
     "strict": true,
     "target": "esnext"
   },
-  "include": [
-    "src/**/*"
-  ],
-  "exclude": [
-    "node_modules"
-  ]
+  "include": ["src/**/*"],
+  "exclude": ["node_modules"]
 }

packages/now-cgi/index.js

@@ -5,15 +5,17 @@ const glob = require('@now/build-utils/fs/glob'); // eslint-disable-line import/
 const download = require('@now/build-utils/fs/download'); // eslint-disable-line import/no-extraneous-dependencies
 const { createLambda } = require('@now/build-utils/lambda'); // eslint-disable-line import/no-extraneous-dependencies
 const getWritableDirectory = require('@now/build-utils/fs/get-writable-directory'); // eslint-disable-line import/no-extraneous-dependencies
+const { shouldServe } = require('@now/build-utils'); // eslint-disable-line import/no-extraneous-dependencies
 
 exports.analyze = ({ files, entrypoint }) => files[entrypoint].digest;
 
-exports.build = async ({ files, entrypoint }) => {
+exports.build = async ({
+  workPath, files, entrypoint, meta,
+}) => {
   console.log('downloading files...');
-  const srcDir = await getWritableDirectory();
   const outDir = await getWritableDirectory();
 
-  await download(files, srcDir);
+  await download(files, workPath, meta);
 
   const handlerPath = path.join(__dirname, 'handler');
   await copyFile(handlerPath, path.join(outDir, 'handler'));
@@ -23,7 +25,7 @@ exports.build = async ({ files, entrypoint }) => {
 
   // For now only the entrypoint file is copied into the lambda
   await copyFile(
-    path.join(srcDir, entrypoint),
+    path.join(workPath, entrypoint),
     path.join(outDir, entrypoint),
   );
 
@@ -40,3 +42,5 @@ exports.build = async ({ files, entrypoint }) => {
     [entrypoint]: lambda,
   };
 };
+
+exports.shouldServe = shouldServe;

packages/now-cgi/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/cgi",
-  "version": "0.1.0",
+  "version": "0.1.4",
   "license": "MIT",
   "repository": {
     "type": "git",

packages/now-go/.gitignore

@@ -1,5 +1,6 @@
 node_modules
 *.log
-/?.js
 /go
-/get-exported-function-name
+/analyze
+*.js
+!util/install.js

packages/now-go/go-helpers.js

@@ -1,129 +0,0 @@
-const tar = require('tar');
-const execa = require('execa');
-const fetch = require('node-fetch');
-const { mkdirp } = require('fs-extra');
-const { dirname, join } = require('path');
-const debug = require('debug')('@now/go:go-helpers');
-
-const archMap = new Map([['x64', 'amd64'], ['x86', '386']]);
-const platformMap = new Map([['win32', 'windows']]);
-
-// Location where the `go` binary will be installed after `postinstall`
-const GO_DIR = join(__dirname, 'go');
-const GO_BIN = join(GO_DIR, 'bin/go');
-
-const getPlatform = p => platformMap.get(p) || p;
-const getArch = a => archMap.get(a) || a;
-const getGoUrl = (version, platform, arch) => {
-  const goArch = getArch(arch);
-  const goPlatform = getPlatform(platform);
-  const ext = platform === 'win32' ? 'zip' : 'tar.gz';
-  return `https://dl.google.com/go/go${version}.${goPlatform}-${goArch}.${ext}`;
-};
-
-async function getExportedFunctionName(filePath) {
-  debug('Detecting handler name for %o', filePath);
-  const bin = join(__dirname, 'get-exported-function-name');
-  const args = [filePath];
-  const name = await execa.stdout(bin, args);
-  debug('Detected exported name %o', name);
-  return name;
-}
-
-// Creates a `$GOPATH` directory tree, as per `go help gopath` instructions.
-// Without this, `go` won't recognize the `$GOPATH`.
-function createGoPathTree(goPath, platform, arch) {
-  const tuple = `${getPlatform(platform)}_${getArch(arch)}`;
-  debug('Creating GOPATH directory structure for %o (%s)', goPath, tuple);
-  return Promise.all([
-    mkdirp(join(goPath, 'bin')),
-    mkdirp(join(goPath, 'pkg', tuple)),
-  ]);
-}
-
-async function get({ src } = {}) {
-  const args = ['get'];
-  if (src) {
-    debug('Fetching `go` dependencies for file %o', src);
-    args.push(src);
-  } else {
-    debug('Fetching `go` dependencies for cwd %o', this.cwd);
-  }
-  await this(...args);
-}
-
-async function build({ src, dest }) {
-  debug('Building `go` binary %o -> %o', src, dest);
-  let sources;
-  if (Array.isArray(src)) {
-    sources = src;
-  } else {
-    sources = [src];
-  }
-  await this('build', '-o', dest, ...sources);
-}
-
-async function createGo(
-  goPath,
-  platform = process.platform,
-  arch = process.arch,
-  opts = {},
-  goMod = false,
-) {
-  const env = {
-    ...process.env,
-    PATH: `${dirname(GO_BIN)}:${process.env.PATH}`,
-    GOPATH: goPath,
-    ...opts.env,
-  };
-
-  if (goMod) {
-    env.GO111MODULE = 'on';
-  }
-
-  function go(...args) {
-    debug('Exec %o', `go ${args.join(' ')}`);
-    return execa('go', args, { stdio: 'inherit', ...opts, env });
-  }
-  go.cwd = opts.cwd || process.cwd();
-  go.get = get;
-  go.build = build;
-  go.goPath = goPath;
-  await createGoPathTree(goPath, platform, arch);
-  return go;
-}
-
-async function downloadGo(
-  dir = GO_DIR,
-  version = '1.12',
-  platform = process.platform,
-  arch = process.arch,
-) {
-  debug('Installing `go` v%s to %o for %s %s', version, dir, platform, arch);
-
-  const url = getGoUrl(version, platform, arch);
-  debug('Downloading `go` URL: %o', url);
-  const res = await fetch(url);
-
-  if (!res.ok) {
-    throw new Error(`Failed to download: ${url} (${res.status})`);
-  }
-
-  // TODO: use a zip extractor when `ext === "zip"`
-  await mkdirp(dir);
-  await new Promise((resolve, reject) => {
-    res.body
-      .on('error', reject)
-      .pipe(tar.extract({ cwd: dir, strip: 1 }))
-      .on('error', reject)
-      .on('finish', resolve);
-  });
-
-  return createGo(dir, platform, arch);
-}
-
-module.exports = {
-  createGo,
-  downloadGo,
-  getExportedFunctionName,
-};

packages/now-go/go-helpers.ts

@@ -0,0 +1,170 @@
+import tar from 'tar';
+import execa from 'execa';
+import fetch from 'node-fetch';
+import { mkdirp, pathExists } from 'fs-extra';
+import { dirname, join } from 'path';
+import { homedir } from 'os';
+import Debug from 'debug';
+
+const debug = Debug('@now/go:go-helpers');
+const archMap = new Map([['x64', 'amd64'], ['x86', '386']]);
+const platformMap = new Map([['win32', 'windows']]);
+
+// Location where the `go` binary will be installed after `postinstall`
+const GO_DIR = join(__dirname, 'go');
+const GO_BIN = join(GO_DIR, 'bin/go');
+
+const getPlatform = (p: string) => platformMap.get(p) || p;
+const getArch = (a: string) => archMap.get(a) || a;
+const getGoUrl = (version: string, platform: string, arch: string) => {
+  const goArch = getArch(arch);
+  const goPlatform = getPlatform(platform);
+  const ext = platform === 'win32' ? 'zip' : 'tar.gz';
+  return `https://dl.google.com/go/go${version}.${goPlatform}-${goArch}.${ext}`;
+};
+
+export async function getAnalyzedEntrypoint(filePath: string, modulePath = '') {
+  debug('Analyzing entrypoint %o', filePath);
+  const bin = join(__dirname, 'analyze');
+
+  const isAnalyzeExist = await pathExists(bin);
+  if (!isAnalyzeExist) {
+    const src = join(__dirname, 'util', 'analyze.go');
+    const dest = join(__dirname, 'analyze');
+    const go = await downloadGo();
+    await go.build(src, dest);
+  }
+
+  const args = [`-modpath=${modulePath}`, filePath];
+
+  const analyzed = await execa.stdout(bin, args);
+  debug('Analyzed entrypoint %o', analyzed);
+  return analyzed;
+}
+
+// Creates a `$GOPATH` directory tree, as per `go help gopath` instructions.
+// Without this, `go` won't recognize the `$GOPATH`.
+function createGoPathTree(goPath: string, platform: string, arch: string) {
+  const tuple = `${getPlatform(platform)}_${getArch(arch)}`;
+  debug('Creating GOPATH directory structure for %o (%s)', goPath, tuple);
+  return Promise.all([
+    mkdirp(join(goPath, 'bin')),
+    mkdirp(join(goPath, 'pkg', tuple)),
+  ]);
+}
+
+class GoWrapper {
+  private env: { [key: string]: string };
+  private opts: execa.Options;
+
+  constructor(env: { [key: string]: string }, opts: execa.Options = {}) {
+    if (!opts.cwd) {
+      opts.cwd = process.cwd();
+    }
+    this.env = env;
+    this.opts = opts;
+  }
+
+  private execute(...args: string[]) {
+    const { opts, env } = this;
+    debug('Exec %o', `go ${args.join(' ')}`);
+    return execa('go', args, { stdio: 'inherit', ...opts, env });
+  }
+
+  mod() {
+    return this.execute('mod', 'tidy');
+  }
+
+  get(src?: string) {
+    const args = ['get'];
+    if (src) {
+      debug('Fetching `go` dependencies for file %o', src);
+      args.push(src);
+    } else {
+      debug('Fetching `go` dependencies for cwd %o', this.opts.cwd);
+    }
+    return this.execute(...args);
+  }
+
+  build(src: string | string[], dest: string, ldsflags = '-s -w') {
+    debug('Building optimized `go` binary %o -> %o', src, dest);
+    const sources = Array.isArray(src) ? src : [src];
+    return this.execute('build', '-ldflags', ldsflags, '-o', dest, ...sources);
+  }
+}
+
+export async function createGo(
+  goPath: string,
+  platform = process.platform,
+  arch = process.arch,
+  opts: execa.Options = {},
+  goMod = false
+) {
+  const path = `${dirname(GO_BIN)}:${process.env.PATH}`;
+  const env: { [key: string]: string } = {
+    ...process.env,
+    PATH: path,
+    GOPATH: goPath,
+    ...opts.env,
+  };
+  if (goMod) {
+    env.GO111MODULE = 'on';
+  }
+  await createGoPathTree(goPath, platform, arch);
+  return new GoWrapper(env, opts);
+}
+
+export async function downloadGo(
+  dir = GO_DIR,
+  version = '1.12',
+  platform = process.platform,
+  arch = process.arch
+) {
+  // Check default `Go` in user machine
+  const isUserGo = await pathExists(join(homedir(), 'go'));
+
+  // If we found GOPATH in ENV, or default `Go` path exists
+  // asssume that user have `Go` installed
+  if (isUserGo || process.env.GOPATH !== undefined) {
+    const { stdout } = await execa('go', ['version']);
+
+    if (parseInt(stdout.split('.')[1]) >= 11) {
+      return createGo(dir, platform, arch);
+    }
+
+    throw new Error(
+      `Your current ${stdout} doesn't support Go Modules. Please update.`
+    );
+  } else {
+    // Check `Go` bin in builder CWD
+    const isGoExist = await pathExists(join(dir, 'bin'));
+    if (!isGoExist) {
+      debug(
+        'Installing `go` v%s to %o for %s %s',
+        version,
+        dir,
+        platform,
+        arch
+      );
+      const url = getGoUrl(version, platform, arch);
+      debug('Downloading `go` URL: %o', url);
+      console.log('Downloading Go ...');
+      const res = await fetch(url);
+
+      if (!res.ok) {
+        throw new Error(`Failed to download: ${url} (${res.status})`);
+      }
+
+      // TODO: use a zip extractor when `ext === "zip"`
+      await mkdirp(dir);
+      await new Promise((resolve, reject) => {
+        res.body
+          .on('error', reject)
+          .pipe(tar.extract({ cwd: dir, strip: 1 }))
+          .on('error', reject)
+          .on('finish', resolve);
+      });
+    }
+    return createGo(dir, platform, arch);
+  }
+}

packages/now-go/index.js

@@ -1,210 +0,0 @@
-const { join, sep, dirname } = require('path');
-const {
-  readFile, writeFile, pathExists, move,
-} = require('fs-extra');
-
-const glob = require('@now/build-utils/fs/glob.js'); // eslint-disable-line import/no-extraneous-dependencies
-const download = require('@now/build-utils/fs/download.js'); // eslint-disable-line import/no-extraneous-dependencies
-const { createLambda } = require('@now/build-utils/lambda.js'); // eslint-disable-line import/no-extraneous-dependencies
-const getWritableDirectory = require('@now/build-utils/fs/get-writable-directory.js'); // eslint-disable-line import/no-extraneous-dependencies
-const { createGo, getExportedFunctionName } = require('./go-helpers');
-
-const config = {
-  maxLambdaSize: '10mb',
-};
-
-async function build({ files, entrypoint }) {
-  console.log('Downloading user files...');
-
-  const [goPath, outDir] = await Promise.all([
-    getWritableDirectory(),
-    getWritableDirectory(),
-  ]);
-
-  const srcPath = join(goPath, 'src', 'lambda');
-  const downloadedFiles = await download(files, srcPath);
-
-  console.log(`Parsing AST for "${entrypoint}"`);
-  let parseFunctionName;
-  try {
-    parseFunctionName = await getExportedFunctionName(
-      downloadedFiles[entrypoint].fsPath,
-    );
-  } catch (err) {
-    console.log(`Failed to parse AST for "${entrypoint}"`);
-    throw err;
-  }
-
-  if (!parseFunctionName) {
-    const err = new Error(
-      `Could not find an exported function in "${entrypoint}"`,
-    );
-    console.log(err.message);
-    throw err;
-  }
-
-  const handlerFunctionName = parseFunctionName.split(',')[0];
-
-  console.log(
-    `Found exported function "${handlerFunctionName}" in "${entrypoint}"`,
-  );
-
-  // we need `main.go` in the same dir as the entrypoint,
-  // otherwise `go build` will refuse to build
-  const entrypointDirname = dirname(downloadedFiles[entrypoint].fsPath);
-
-  // check if package name other than main
-  const packageName = parseFunctionName.split(',')[1];
-  const isGoModExist = await pathExists(join(entrypointDirname, 'go.mod'));
-  if (packageName !== 'main') {
-    const go = await createGo(
-      goPath,
-      process.platform,
-      process.arch,
-      {
-        cwd: entrypointDirname,
-      },
-      true,
-    );
-    if (!isGoModExist) {
-      try {
-        const defaultGoModContent = `module ${packageName}`;
-
-        await writeFile(join(entrypointDirname, 'go.mod'), defaultGoModContent);
-      } catch (err) {
-        console.log(`failed to create default go.mod for ${packageName}`);
-        throw err;
-      }
-    }
-
-    const mainModGoFileName = 'main__mod__.go';
-    const modMainGoContents = await readFile(
-      join(__dirname, mainModGoFileName),
-      'utf8',
-    );
-
-    let goPackageName = `${packageName}/${packageName}`;
-    const goFuncName = `${packageName}.${handlerFunctionName}`;
-
-    if (isGoModExist) {
-      const goModContents = await readFile(
-        join(entrypointDirname, 'go.mod'),
-        'utf8',
-      );
-      goPackageName = `${
-        goModContents.split('\n')[0].split(' ')[1]
-      }/${packageName}`;
-    }
-
-    const mainModGoContents = modMainGoContents
-      .replace('__NOW_HANDLER_PACKAGE_NAME', goPackageName)
-      .replace('__NOW_HANDLER_FUNC_NAME', goFuncName);
-
-    // write main__mod__.go
-    await writeFile(
-      join(entrypointDirname, mainModGoFileName),
-      mainModGoContents,
-    );
-
-    // move user go file to folder
-    try {
-      // default path
-      let finalDestination = join(entrypointDirname, packageName, entrypoint);
-      const entrypointArr = entrypoint.split(sep);
-
-      // if `entrypoint` include folder, only use filename
-      if (entrypointArr.length > 1) {
-        finalDestination = join(
-          entrypointDirname,
-          packageName,
-          entrypointArr.pop(),
-        );
-      }
-
-      await move(downloadedFiles[entrypoint].fsPath, finalDestination);
-    } catch (err) {
-      console.log('failed to move entry to package folder');
-      throw err;
-    }
-
-    console.log('tidy go.mod file');
-    try {
-      // ensure go.mod up-to-date
-      await go('mod', 'tidy');
-    } catch (err) {
-      console.log('failed to `go mod tidy`');
-      throw err;
-    }
-
-    console.log('Running `go build`...');
-    const destPath = join(outDir, 'handler');
-    try {
-      const src = [join(entrypointDirname, mainModGoFileName)];
-      await go.build({ src, dest: destPath });
-    } catch (err) {
-      console.log('failed to `go build`');
-      throw err;
-    }
-  } else {
-    const go = await createGo(
-      goPath,
-      process.platform,
-      process.arch,
-      {
-        cwd: entrypointDirname,
-      },
-      false,
-    );
-    const origianlMainGoContents = await readFile(
-      join(__dirname, 'main.go'),
-      'utf8',
-    );
-    const mainGoContents = origianlMainGoContents.replace(
-      '__NOW_HANDLER_FUNC_NAME',
-      handlerFunctionName,
-    );
-
-    // in order to allow the user to have `main.go`,
-    // we need our `main.go` to be called something else
-    const mainGoFileName = 'main__now__go__.go';
-
-    // Go doesn't like to build files in different directories,
-    // so now we place `main.go` together with the user code
-    await writeFile(join(entrypointDirname, mainGoFileName), mainGoContents);
-
-    // `go get` will look at `*.go` (note we set `cwd`), parse the `import`s
-    // and download any packages that aren't part of the stdlib
-    try {
-      await go.get();
-    } catch (err) {
-      console.log('failed to `go get`');
-      throw err;
-    }
-
-    console.log('Running `go build`...');
-    const destPath = join(outDir, 'handler');
-    try {
-      const src = [
-        join(entrypointDirname, mainGoFileName),
-        downloadedFiles[entrypoint].fsPath,
-      ];
-      await go.build({ src, dest: destPath });
-    } catch (err) {
-      console.log('failed to `go build`');
-      throw err;
-    }
-  }
-
-  const lambda = await createLambda({
-    files: await glob('**', outDir),
-    handler: 'handler',
-    runtime: 'go1.x',
-    environment: {},
-  });
-
-  return {
-    [entrypoint]: lambda,
-  };
-}
-
-module.exports = { config, build };

packages/now-go/index.ts

@@ -0,0 +1,388 @@
+import { join, sep, dirname, basename } from 'path';
+import { readFile, writeFile, pathExists, move } from 'fs-extra';
+import { homedir } from 'os';
+import execa from 'execa';
+
+import {
+  glob,
+  download,
+  createLambda,
+  getWriteableDirectory,
+  BuildOptions,
+  shouldServe,
+  Files,
+} from '@now/build-utils';
+
+import { createGo, getAnalyzedEntrypoint } from './go-helpers';
+
+interface Analyzed {
+  found?: boolean;
+  packageName: string;
+  functionName: string;
+  watch: string[];
+}
+interface BuildParamsMeta {
+  isDev: boolean | undefined;
+}
+interface BuildParamsType extends BuildOptions {
+  files: Files;
+  entrypoint: string;
+  workPath: string;
+  meta: BuildParamsMeta;
+}
+
+// Initialize private git repo for Go Modules
+async function initPrivateGit(credentials: string) {
+  await execa('git', [
+    'config',
+    '--global',
+    'credential.helper',
+    `store --file ${join(homedir(), '.git-credentials')}`,
+  ]);
+
+  await writeFile(join(homedir(), '.git-credentials'), credentials);
+}
+
+export const version = 2;
+
+export const config = {
+  maxLambdaSize: '10mb',
+};
+
+export async function build({
+  files,
+  entrypoint,
+  config,
+  workPath,
+  meta = {} as BuildParamsMeta,
+}: BuildParamsType) {
+  if (process.env.GIT_CREDENTIALS && !meta.isDev) {
+    console.log('Initialize Git credentials...');
+    await initPrivateGit(process.env.GIT_CREDENTIALS);
+  }
+
+  console.log('Downloading user files...');
+  const entrypointArr = entrypoint.split(sep);
+
+  let [goPath, outDir] = await Promise.all([
+    getWriteableDirectory(),
+    getWriteableDirectory(),
+  ]);
+
+  const srcPath = join(goPath, 'src', 'lambda');
+  let downloadedFiles;
+  if (meta.isDev) {
+    downloadedFiles = await download(files, workPath, meta);
+  } else {
+    downloadedFiles = await download(files, srcPath);
+  }
+
+  console.log(`Parsing AST for "${entrypoint}"`);
+  let analyzed: string;
+  try {
+    let goModAbsPathDir = '';
+    for (const file of Object.keys(downloadedFiles)) {
+      if (file === 'go.mod') {
+        goModAbsPathDir = dirname(downloadedFiles[file].fsPath);
+      }
+    }
+    analyzed = await getAnalyzedEntrypoint(
+      downloadedFiles[entrypoint].fsPath,
+      goModAbsPathDir
+    );
+  } catch (err) {
+    console.log(`Failed to parse AST for "${entrypoint}"`);
+    throw err;
+  }
+
+  if (!analyzed) {
+    const err = new Error(
+      `Could not find an exported function in "${entrypoint}"
+Learn more: https://zeit.co/docs/v2/deployments/official-builders/go-now-go/#entrypoint
+      `
+    );
+    console.log(err.message);
+    throw err;
+  }
+
+  const parsedAnalyzed = JSON.parse(analyzed) as Analyzed;
+
+  if (meta.isDev) {
+    const base = dirname(downloadedFiles['now.json'].fsPath);
+    const destNow = join(
+      base,
+      '.now',
+      'cache',
+      basename(entrypoint, '.go'),
+      'src',
+      'lambda'
+    );
+    // this will ensure Go rebuilt fast
+    goPath = join(base, '.now', 'cache', basename(entrypoint, '.go'));
+    await download(downloadedFiles, destNow);
+
+    downloadedFiles = await glob('**', destNow);
+  }
+
+  // find `go.mod` in downloadedFiles
+  const entrypointDirname = dirname(downloadedFiles[entrypoint].fsPath);
+  let isGoModExist = false;
+  let goModPath = '';
+  let goModPathArr: string[] = [];
+  for (const file of Object.keys(downloadedFiles)) {
+    const fileDirname = dirname(downloadedFiles[file].fsPath);
+    if (file === 'go.mod') {
+      isGoModExist = true;
+      goModPath = fileDirname;
+      goModPathArr = goModPath.split(sep);
+    } else if (file.includes('go.mod')) {
+      isGoModExist = true;
+      if (entrypointDirname === fileDirname) {
+        goModPath = fileDirname;
+        goModPathArr = goModPath.split(sep);
+      }
+    }
+  }
+
+  const input = entrypointDirname;
+  var includedFiles: Files = {};
+
+  if (config && config.includeFiles) {
+    for (const pattern of config.includeFiles) {
+      const files = await glob(pattern, input);
+      for (const assetName of Object.keys(files)) {
+        includedFiles[assetName] = files[assetName];
+      }
+    }
+  }
+
+  const handlerFunctionName = parsedAnalyzed.functionName;
+  console.log(
+    `Found exported function "${handlerFunctionName}" in "${entrypoint}"`
+  );
+
+  // check if package name other than main
+  // using `go.mod` way building the handler
+  const packageName = parsedAnalyzed.packageName;
+
+  if (isGoModExist && packageName === 'main') {
+    throw new Error('Please change `package main` to `package handler`');
+  }
+
+  if (packageName !== 'main') {
+    const go = await createGo(
+      goPath,
+      process.platform,
+      process.arch,
+      {
+        cwd: entrypointDirname,
+      },
+      true
+    );
+    if (!isGoModExist) {
+      try {
+        const defaultGoModContent = `module ${packageName}`;
+
+        await writeFile(join(entrypointDirname, 'go.mod'), defaultGoModContent);
+      } catch (err) {
+        console.log(`failed to create default go.mod for ${packageName}`);
+        throw err;
+      }
+    }
+
+    const mainModGoFileName = 'main__mod__.go';
+    const modMainGoContents = await readFile(
+      join(__dirname, mainModGoFileName),
+      'utf8'
+    );
+
+    let goPackageName = `${packageName}/${packageName}`;
+    const goFuncName = `${packageName}.${handlerFunctionName}`;
+
+    if (isGoModExist) {
+      const goModContents = await readFile(join(goModPath, 'go.mod'), 'utf8');
+      const usrModName = goModContents.split('\n')[0].split(' ')[1];
+      goPackageName = `${usrModName}/${packageName}`;
+    }
+
+    const mainModGoContents = modMainGoContents
+      .replace('__NOW_HANDLER_PACKAGE_NAME', goPackageName)
+      .replace('__NOW_HANDLER_FUNC_NAME', goFuncName);
+
+    if (goModPathArr.length > 1) {
+      // using `go.mod` path to write main__mod__.go
+      await writeFile(join(goModPath, mainModGoFileName), mainModGoContents);
+    } else {
+      // using `entrypointDirname` to write main__mod__.go
+      await writeFile(
+        join(entrypointDirname, mainModGoFileName),
+        mainModGoContents
+      );
+    }
+
+    // move user go file to folder
+    try {
+      // default path
+      let finalDestination = join(entrypointDirname, packageName, entrypoint);
+      let forceMove = false;
+
+      if (meta.isDev) {
+        forceMove = true;
+      }
+
+      // if `entrypoint` include folder, only use filename
+      if (entrypointArr.length > 1) {
+        finalDestination = join(
+          entrypointDirname,
+          packageName,
+          entrypointArr[entrypointArr.length - 1]
+        );
+      }
+
+      if (
+        dirname(downloadedFiles[entrypoint].fsPath) === goModPath ||
+        !isGoModExist
+      ) {
+        await move(downloadedFiles[entrypoint].fsPath, finalDestination, {
+          overwrite: forceMove,
+        });
+      }
+    } catch (err) {
+      console.log('failed to move entry to package folder');
+      throw err;
+    }
+
+    if (meta.isDev) {
+      let entrypointDir = entrypointDirname;
+      if (goModPathArr.length > 1) {
+        entrypointDir = goModPath;
+      }
+      const isGoModBk = await pathExists(join(entrypointDir, 'go.mod.bk'));
+      if (isGoModBk) {
+        await move(
+          join(entrypointDir, 'go.mod.bk'),
+          join(entrypointDir, 'go.mod'),
+          { overwrite: true }
+        );
+        await move(
+          join(entrypointDir, 'go.sum.bk'),
+          join(entrypointDir, 'go.sum'),
+          { overwrite: true }
+        );
+      }
+    }
+
+    console.log('Tidy `go.mod` file...');
+    try {
+      // ensure go.mod up-to-date
+      await go.mod();
+    } catch (err) {
+      console.log('failed to `go mod tidy`');
+      throw err;
+    }
+
+    console.log('Running `go build`...');
+    const destPath = join(outDir, 'handler');
+    const isGoModInRootDir = goModPathArr.length === 1;
+    const baseGoModPath = isGoModInRootDir ? entrypointDirname : goModPath;
+    try {
+      let src = [join(baseGoModPath, mainModGoFileName)];
+
+      await go.build(src, destPath, config.ldsflags);
+    } catch (err) {
+      console.log('failed to `go build`');
+      throw err;
+    }
+    if (meta.isDev) {
+      // caching for `now dev`
+      await move(
+        join(baseGoModPath, 'go.mod'),
+        join(baseGoModPath, 'go.mod.bk'),
+        { overwrite: true }
+      );
+      await move(
+        join(baseGoModPath, 'go.sum'),
+        join(baseGoModPath, 'go.sum.bk'),
+        { overwrite: true }
+      );
+    }
+  } else {
+    // legacy mode
+    // we need `main.go` in the same dir as the entrypoint,
+    // otherwise `go build` will refuse to build
+    const go = await createGo(
+      goPath,
+      process.platform,
+      process.arch,
+      {
+        cwd: entrypointDirname,
+      },
+      false
+    );
+    const origianlMainGoContents = await readFile(
+      join(__dirname, 'main.go'),
+      'utf8'
+    );
+    const mainGoContents = origianlMainGoContents.replace(
+      '__NOW_HANDLER_FUNC_NAME',
+      handlerFunctionName
+    );
+
+    // in order to allow the user to have `main.go`,
+    // we need our `main.go` to be called something else
+    const mainGoFileName = 'main__now__go__.go';
+
+    // Go doesn't like to build files in different directories,
+    // so now we place `main.go` together with the user code
+    await writeFile(join(entrypointDirname, mainGoFileName), mainGoContents);
+
+    // `go get` will look at `*.go` (note we set `cwd`), parse the `import`s
+    // and download any packages that aren't part of the stdlib
+    console.log('Running `go get`...');
+    try {
+      await go.get();
+    } catch (err) {
+      console.log('failed to `go get`');
+      throw err;
+    }
+
+    console.log('Running `go build`...');
+    const destPath = join(outDir, 'handler');
+    try {
+      const src = [
+        join(entrypointDirname, mainGoFileName),
+        downloadedFiles[entrypoint].fsPath,
+      ];
+      await go.build(src, destPath);
+    } catch (err) {
+      console.log('failed to `go build`');
+      throw err;
+    }
+  }
+
+  const lambda = await createLambda({
+    files: { ...(await glob('**', outDir)), ...includedFiles },
+    handler: 'handler',
+    runtime: 'go1.x',
+    environment: {},
+  });
+  const output = {
+    [entrypoint]: lambda,
+  };
+
+  let watch = parsedAnalyzed.watch;
+  let watchSub: string[] = [];
+  // if `entrypoint` located in subdirectory
+  // we will need to concat it with return watch array
+  if (entrypointArr.length > 1) {
+    entrypointArr.pop();
+    watchSub = parsedAnalyzed.watch.map(file => join(...entrypointArr, file));
+  }
+
+  return {
+    output,
+    watch: watch.concat(watchSub),
+  };
+}
+
+export { shouldServe };

packages/now-go/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/go",
-  "version": "0.4.0",
+  "version": "0.5.1",
   "license": "MIT",
   "repository": {
     "type": "git",
@@ -8,7 +8,9 @@
     "directory": "packages/now-go"
   },
   "scripts": {
-    "postinstall": "node ./util/install"
+    "build": "tsc",
+    "test": "tsc && jest",
+    "prepublish": "tsc"
   },
   "files": [
     "*.js",
@@ -20,8 +22,15 @@
     "debug": "^4.1.1",
     "execa": "^1.0.0",
     "fs-extra": "^7.0.0",
-    "mkdirp-promise": "5.0.1",
     "node-fetch": "^2.2.1",
     "tar": "4.4.6"
+  },
+  "devDependencies": {
+    "@types/debug": "^4.1.3",
+    "@types/execa": "^0.9.0",
+    "@types/fs-extra": "^5.0.5",
+    "@types/node-fetch": "^2.3.0",
+    "@types/tar": "^4.0.0",
+    "typescript": "^3.4.2"
   }
 }

packages/now-go/test/fixtures/03-env-vars/build-env/go.mod

@@ -0,0 +1 @@
+module build-env

packages/now-go/test/fixtures/03-env-vars/build-env/index.go

@@ -0,0 +1,17 @@
+package buildenv
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+)
+
+// Handler function
+func Handler(w http.ResponseWriter, r *http.Request) {
+	rdm := os.Getenv("RANDOMNESS_BUILD_ENV")
+	if rdm == "" {
+		fmt.Println("No build env received")
+	}
+
+	fmt.Fprintf(w, rdm+":build-env")
+}

packages/now-go/test/fixtures/03-env-vars/env/go.mod

@@ -0,0 +1 @@
+module env

packages/now-go/test/fixtures/03-env-vars/env/index.go

@@ -0,0 +1,17 @@
+package env
+
+import (
+	"fmt"
+	"net/http"
+	"os"
+)
+
+// Handler function
+func Handler(w http.ResponseWriter, r *http.Request) {
+	rdm := os.Getenv("RANDOMNESS_ENV")
+	if rdm == "" {
+		fmt.Println("No env received")
+	}
+
+	fmt.Fprintf(w, rdm)
+}

packages/now-go/test/fixtures/03-env-vars/now.json

@@ -0,0 +1,18 @@
+{
+  "version": 2,
+  "builds": [
+    {
+      "src": "env/index.go",
+      "use": "@now/go"
+    }
+  ],
+  "env": {
+    "RANDOMNESS_ENV": "RANDOMNESS_PLACEHOLDER"
+  },
+  "probes": [
+    {
+      "path": "/env",
+      "mustContain": "RANDOMNESS_PLACEHOLDER"
+    }
+  ]
+}

packages/now-go/test/fixtures/06-content-type/index.go

@@ -0,0 +1,11 @@
+package function
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Handler function
+func Handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "RANDOMNESS_PLACEHOLDER")
+}

packages/now-go/test/fixtures/06-content-type/now.json

@@ -0,0 +1,4 @@
+{
+  "version": 2,
+  "builds": [{ "src": "index.go", "use": "@now/go" }]
+}

packages/now-go/test/fixtures/07-content-length/now.json

@@ -0,0 +1,7 @@
+{
+  "version": 2,
+  "builds": [{ "src": "*.go", "use": "@now/go" }],
+  "env": {
+    "RANDOMNESS_ENV_VAR": "RANDOMNESS_PLACEHOLDER"
+  }
+}

packages/now-go/test/fixtures/07-content-length/test1.go

@@ -0,0 +1,16 @@
+package function
+
+import (
+	"net/http"
+	"os"
+	"strconv"
+)
+
+// HandlerTest1 function
+func HandlerTest1(w http.ResponseWriter, r *http.Request) {
+	rdm := os.Getenv("RANDOMNESS_ENV_VAR")
+
+	w.WriteHeader(401)
+	w.Header().Set("content-length", strconv.Itoa(len(rdm+":content-length")))
+	w.Write([]byte(rdm + ":content-length"))
+}

packages/now-go/test/fixtures/07-content-length/test2.go

@@ -0,0 +1,12 @@
+package function
+
+import (
+	"net/http"
+)
+
+// HandlerTest2 function
+func HandlerTest2(w http.ResponseWriter, r *http.Request) {
+	w.Header().Set("Content-Length", "2")
+	w.WriteHeader(401)
+	w.Write([]byte(""))
+}

packages/now-go/test/fixtures/07-content-length/test3.go

@@ -0,0 +1,13 @@
+package function
+
+import (
+	"net/http"
+	"os"
+)
+
+// HandlerTest3 function
+func HandlerTest3(w http.ResponseWriter, r *http.Request) {
+	rev := os.Getenv("RANDOMNESS_ENV_VAR")
+	w.WriteHeader(401)
+	w.Write([]byte(rev + ":content-length"))
+}

packages/now-go/test/fixtures/08-include-files/index.go

@@ -0,0 +1,16 @@
+package cowsay
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http"
+)
+
+// Handler function
+func Handler(w http.ResponseWriter, r *http.Request) {
+	bts, err := ioutil.ReadFile("templates/foo.txt")
+	if err != nil {
+		http.Error(w, err.Error(), http.StatusInternalServerError)
+	}
+	fmt.Fprintf(w, string(bts))
+}

packages/now-go/test/fixtures/08-include-files/now.json

@@ -0,0 +1,18 @@
+{
+  "version": 2,
+  "builds": [
+    {
+      "src": "index.go",
+      "use": "@now/go",
+      "config": {
+        "includeFiles": ["templates/**"]
+      }
+    }
+  ],
+  "probes": [
+    {
+      "path": "/",
+      "mustContain": "foobar from file"
+    }
+  ]
+}

packages/now-go/test/fixtures/08-include-files/templates/foo.txt

@@ -0,0 +1 @@
+foobar from file

packages/now-go/test/fixtures/09-exported-function/index.go

@@ -0,0 +1,22 @@
+package function
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Person struct
+type Person struct {
+	name string
+	age  int
+}
+
+// NewPerson struct method
+func NewPerson(name string, age int) *Person {
+	return &Person{name: name, age: age}
+}
+
+// H func
+func H(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "RANDOMNESS_PLACEHOLDER")
+}

packages/now-go/test/fixtures/09-exported-function/now.json

@@ -0,0 +1,5 @@
+{
+  "version": 2,
+  "builds": [{ "src": "index.go", "use": "@now/go" }],
+  "probes": [{ "path": "/", "mustContain": "RANDOMNESS_PLACEHOLDER" }]
+}

packages/now-go/test/fixtures/10-go-mod/go.mod

@@ -0,0 +1,3 @@
+module go-mod
+
+go 1.12

packages/now-go/test/fixtures/10-go-mod/index.go

@@ -0,0 +1,11 @@
+package handler
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Handler func
+func Handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "RANDOMNESS_PLACEHOLDER")
+}

packages/now-go/test/fixtures/10-go-mod/now.json

@@ -0,0 +1,5 @@
+{
+  "version": 2,
+  "builds": [{ "src": "index.go", "use": "@now/go" }],
+  "probes": [{ "path": "/", "mustContain": "RANDOMNESS_PLACEHOLDER" }]
+}

packages/now-go/test/fixtures/11-go-mod-shared/api/index.go

@@ -0,0 +1,12 @@
+package api
+
+import (
+	"fmt"
+	"net/http"
+	"with-shared/shared"
+)
+
+// Handler func
+func Handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, shared.Say("RANDOMNESS_PLACEHOLDER"))
+}

packages/now-go/test/fixtures/11-go-mod-shared/go.mod

@@ -0,0 +1,3 @@
+module with-shared
+
+go 1.12

packages/now-go/test/fixtures/11-go-mod-shared/now.json

@@ -0,0 +1,5 @@
+{
+  "version": 2,
+  "builds": [{ "src": "api/*.go", "use": "@now/go" }],
+  "probes": [{ "path": "/api", "mustContain": "RANDOMNESS_PLACEHOLDER" }]
+}

packages/now-go/test/fixtures/11-go-mod-shared/shared/shared.go

@@ -0,0 +1,6 @@
+package shared
+
+// Say func
+func Say(text string) string {
+	return text
+}

packages/now-go/test/fixtures/12-go-mod-subs/now.json

@@ -0,0 +1,8 @@
+{
+  "version": 2,
+  "builds": [{ "src": "**/*.go", "use": "@now/go" }],
+  "probes": [
+    { "path": "/sub-1", "mustContain": "RANDOMNESS_PLACEHOLDER" },
+    { "path": "/sub-2", "mustContain": "RANDOMNESS_PLACEHOLDER" }
+  ]
+}

packages/now-go/test/fixtures/12-go-mod-subs/sub-1/go.mod

@@ -0,0 +1,3 @@
+module sub-1
+
+go 1.12

packages/now-go/test/fixtures/12-go-mod-subs/sub-1/index.go

@@ -0,0 +1,11 @@
+package sub1
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Handler func
+func Handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "RANDOMNESS_PLACEHOLDER")
+}

packages/now-go/test/fixtures/12-go-mod-subs/sub-2/go.mod

@@ -0,0 +1,3 @@
+module sub-2
+
+go 1.12

packages/now-go/test/fixtures/12-go-mod-subs/sub-2/index.go

@@ -0,0 +1,11 @@
+package sub2
+
+import (
+	"fmt"
+	"net/http"
+)
+
+// Handler func
+func Handler(w http.ResponseWriter, r *http.Request) {
+	fmt.Fprintf(w, "RANDOMNESS_PLACEHOLDER")
+}

packages/now-go/test/test.js

@@ -26,8 +26,8 @@ for (const fixture of fs.readdirSync(fixturesPath)) {
     await expect(
       testDeployment(
         { builderUrl, buildUtilsUrl },
-        path.join(fixturesPath, fixture),
-      ),
+        path.join(fixturesPath, fixture)
+      )
     ).resolves.toBeDefined();
   });
 }

packages/now-go/tsconfig.json

@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "declaration": false,
+    "esModuleInterop": true,
+    "lib": ["esnext"],
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "noEmitOnError": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitThis": false,
+    "types": ["node"],
+    "strict": true,
+    "target": "esnext"
+  }
+}

packages/now-go/util/analyze.go

@@ -0,0 +1,215 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var ignoredFoldersRegex []*regexp.Regexp
+
+func init() {
+	ignoredFolders := []string{"vendor", "testdata", ".now"}
+
+	// Build the regex that matches if a path contains the respective ignored folder
+	// The pattern will look like: (.*/)?vendor/.*, which matches every path that contains a vendor folder
+	for _, folder := range ignoredFolders {
+		ignoredFoldersRegex = append(ignoredFoldersRegex, regexp.MustCompile("(.*/)?"+folder+"/.*"))
+	}
+}
+
+type analyze struct {
+	PackageName string   `json:"packageName"`
+	FuncName    string   `json:"functionName"`
+	Watch       []string `json:"watch"`
+}
+
+// parse go file
+func parse(fileName string) *ast.File {
+	fset := token.NewFileSet()
+	parsed, err := parser.ParseFile(fset, fileName, nil, parser.ParseComments)
+	if err != nil {
+		log.Fatalf("Could not parse Go file \"%s\"\n", fileName)
+		os.Exit(1)
+	}
+
+	return parsed
+}
+
+// ensure we only working with interest go file(s)
+func visit(files *[]string) filepath.WalkFunc {
+	return func(path string, info os.FileInfo, err error) error {
+		itf, err := filepath.Match("*test.go", path)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		// we don't need Dirs, or test files
+		// we only want `.go` files. Further, we ignore
+		// every file that is in one of the ignored folders.
+		if info.IsDir() || itf || filepath.Ext(path) != ".go" || isInIgnoredFolder(path) {
+			return nil
+		}
+
+		*files = append(*files, path)
+		return nil
+	}
+}
+
+// isInIgnoredFolder checks if the given path is in one of the ignored folders.
+func isInIgnoredFolder(path string) bool {
+	// Make sure the regex works for Windows paths
+	path = filepath.ToSlash(path)
+
+	for _, pattern := range ignoredFoldersRegex {
+		if pattern.MatchString(path) {
+			return true
+		}
+	}
+	return false
+}
+
+// return unique file
+func unique(files []string) []string {
+	encountered := map[string]bool{}
+	for v := range files {
+		encountered[files[v]] = true
+	}
+
+	result := []string{}
+	for key := range encountered {
+		result = append(result, key)
+	}
+	return result
+}
+
+func main() {
+	if len(os.Args) != 3 {
+		// Args should have the program name on `0`
+		// and the file name on `1`
+		fmt.Println("Wrong number of args; Usage is:\n  ./go-analyze -modpath=module-path file_name.go")
+		os.Exit(1)
+	}
+	fileName := os.Args[2]
+	rf, err := ioutil.ReadFile(fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	se := string(rf)
+
+	var files []string
+	var relatedFiles []string
+
+	// Add entrypoint to watchlist
+	relFileName, err := filepath.Rel(filepath.Dir(fileName), fileName)
+	if err != nil {
+		log.Fatal(err)
+	}
+	relatedFiles = append(relatedFiles, relFileName)
+
+	// looking for all go files that have export func
+	// using in entrypoint
+	err = filepath.Walk(filepath.Dir(fileName), visit(&files))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// looking related packages
+	var modPath string
+	flag.StringVar(&modPath, "modpath", "", "module path")
+	flag.Parse()
+	if len(modPath) > 1 {
+		err = filepath.Walk(modPath, visit(&files))
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+
+	for _, file := range files {
+		absFileName, _ := filepath.Abs(fileName)
+		absFile, _ := filepath.Abs(file)
+		// if it isn't entrypoint
+		if absFileName != absFile {
+			// find all export structs and functions
+			pf := parse(file)
+			var exportedDecl []string
+
+			ast.Inspect(pf, func(n ast.Node) bool {
+				switch t := n.(type) {
+				case *ast.FuncDecl:
+					if t.Name.IsExported() {
+						exportedDecl = append(exportedDecl, t.Name.Name)
+					}
+				// find variable declarations
+				case *ast.TypeSpec:
+					// which are public
+					if t.Name.IsExported() {
+						switch t.Type.(type) {
+						// and are interfaces
+						case *ast.StructType:
+							exportedDecl = append(exportedDecl, t.Name.Name)
+						}
+					}
+				}
+				return true
+			})
+
+			for _, ed := range exportedDecl {
+				if strings.Contains(se, ed) {
+					// find relative path of related file
+					var basePath string
+					if modPath == "" {
+						basePath = filepath.Dir(fileName)
+					} else {
+						basePath = modPath
+					}
+
+					rel, err := filepath.Rel(basePath, file)
+					if err != nil {
+						log.Fatal(err)
+					}
+					relatedFiles = append(relatedFiles, rel)
+				}
+			}
+		}
+	}
+
+	parsed := parse(fileName)
+	offset := parsed.Pos()
+	reqRep := "*http.Request http.ResponseWriter"
+
+	for _, decl := range parsed.Decls {
+		fn, ok := decl.(*ast.FuncDecl)
+		if !ok {
+			// this declaration is not a function
+			// so we're not interested
+			continue
+		}
+		if fn.Name.IsExported() == true {
+			// find a valid `net/http` handler function
+			for _, param := range fn.Type.Params.List {
+				if strings.Contains(reqRep, string(rf[param.Type.Pos()-offset:param.Type.End()-offset])) {
+					// we found the first exported function with `net/http`
+					// we're done!
+					analyzed := analyze{
+						PackageName: parsed.Name.Name,
+						FuncName:    fn.Name.Name,
+						Watch:       unique(relatedFiles),
+					}
+					analyzedJSON, _ := json.Marshal(analyzed)
+					fmt.Print(string(analyzedJSON))
+					os.Exit(0)
+				}
+			}
+		}
+	}
+}

packages/now-go/util/get-exported-function-name.go

@@ -1,41 +0,0 @@
-package main
-
-import (
-	"fmt"
-	"go/ast"
-	"go/parser"
-	"go/token"
-	"os"
-)
-
-func main() {
-	if len(os.Args) != 2 {
-		// Args should have the program name on `0`
-		// and the file name on `1`
-		fmt.Println("Wrong number of args; Usage is:\n  ./get-exported-function-name file_name.go")
-		os.Exit(1)
-	}
-	fileName := os.Args[1]
-	fset := token.NewFileSet()
-
-	parsed, err := parser.ParseFile(fset, fileName, nil, parser.ParseComments)
-	if err != nil {
-		fmt.Printf("Could not parse Go file \"%s\"\n", fileName)
-		os.Exit(1)
-	}
-
-	for _, decl := range parsed.Decls {
-		fn, ok := decl.(*ast.FuncDecl)
-		if !ok {
-			// this declaraction is not a function
-			// so we're not interested
-			continue
-		}
-		if fn.Name.IsExported() == true {
-			// we found the first exported function
-			// we're done!
-			fmt.Print(fn.Name.Name, ",", parsed.Name.Name)
-			os.Exit(0)
-		}
-	}
-}

packages/now-go/util/install.js

@@ -1,18 +0,0 @@
-const { join } = require('path');
-const { downloadGo } = require('../go-helpers');
-
-async function main() {
-  // First download the `go` binary for this platform/arch.
-  const go = await downloadGo();
-
-  // Build the `get-exported-function-name` helper program.
-  // `go get` is not necessary because the program has no external deps.
-  const src = join(__dirname, 'get-exported-function-name.go');
-  const dest = join(__dirname, '../get-exported-function-name');
-  await go.build({ src, dest });
-}
-
-main().catch((err) => {
-  console.error(err);
-  process.exit(1);
-});

packages/now-html-minifier/index.js

@@ -1,4 +1,4 @@
-const FileBlob = require('@now/build-utils/file-blob.js'); // eslint-disable-line import/no-extraneous-dependencies
+const { FileBlob, shouldServe } = require('@now/build-utils'); // eslint-disable-line import/no-extraneous-dependencies
 const { minify } = require('html-minifier');
 
 const defaultOptions = {
@@ -28,3 +28,5 @@ exports.build = async ({ files, entrypoint, config }) => {
 
   return { [entrypoint]: result };
 };
+
+exports.shouldServe = shouldServe;

packages/now-html-minifier/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/html-minifier",
-  "version": "1.1.0",
+  "version": "1.1.3",
   "license": "MIT",
   "repository": {
     "type": "git",

packages/now-lambda/index.js

@@ -1,5 +1,6 @@
 const { Lambda } = require('@now/build-utils/lambda.js'); // eslint-disable-line import/no-extraneous-dependencies
 const streamToBuffer = require('@now/build-utils/fs/stream-to-buffer.js'); // eslint-disable-line import/no-extraneous-dependencies
+const { shouldServe } = require('@now/build-utils'); // eslint-disable-line import/no-extraneous-dependencies
 
 exports.build = async ({ files, entrypoint, config }) => {
   if (!files[entrypoint]) throw new Error('Entrypoint not found in files');
@@ -10,3 +11,5 @@ exports.build = async ({ files, entrypoint, config }) => {
   const lambda = new Lambda({ zipBuffer, handler, runtime });
   return { [entrypoint]: lambda };
 };
+
+exports.shouldServe = shouldServe;

packages/now-lambda/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@now/lambda",
-  "version": "0.5.0",
+  "version": "0.5.4",
   "license": "MIT",
   "repository": {
     "type": "git",

packages/now-lambda/test/fixtures/01-cowsay/now.json

@@ -1,11 +1,22 @@
 {
   "version": 2,
   "builds": [
-    { "src": "index.zip", "use": "@now/lambda", "config": { "handler": "index.handler", "runtime": "nodejs8.10" } },
-    { "src": "subdirectory/index.zip", "use": "@now/lambda", "config": { "handler": "index.handler", "runtime": "nodejs8.10" } }
+    {
+      "src": "index.zip",
+      "use": "@now/lambda",
+      "config": { "handler": "index.handler", "runtime": "nodejs8.10" }
+    },
+    {
+      "src": "subdirectory/index.zip",
+      "use": "@now/lambda",
+      "config": { "handler": "index.handler", "runtime": "nodejs8.10" }
+    }
   ],
   "probes": [
     { "path": "/", "mustContain": "cow:NO_REPLACE_TO_AVOID_CRC_MISMATCH" },
-    { "path": "/subdirectory/", "mustContain": "yoda:NO_REPLACE_TO_AVOID_CRC_MISMATCH" }
+    {
+      "path": "/subdirectory/",
+      "mustContain": "yoda:NO_REPLACE_TO_AVOID_CRC_MISMATCH"
+    }
   ]
 }

packages/now-layer-node/.gitignore

@@ -0,0 +1 @@
+/dist

packages/now-layer-node/package.json

@@ -0,0 +1,32 @@
+{
+  "name": "@now/layer-node",
+  "version": "0.0.2",
+  "main": "./dist/src/index",
+  "license": "MIT",
+  "files": [
+    "dist"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/zeit/now-builders.git",
+    "directory": "packages/now-layer-node"
+  },
+  "scripts": {
+    "build": "tsc",
+    "test": "tsc && jest",
+    "prepublishOnly": "tsc"
+  },
+  "dependencies": {
+    "fs-extra": "7.0.1",
+    "node-fetch": "2.6.0",
+    "promisepipe": "3.0.0",
+    "stream-to-promise": "2.2.0",
+    "tar": "4.4.6",
+    "yauzl-promise": "2.1.3"
+  },
+  "devDependencies": {
+    "@types/tar": "4.0.0",
+    "@types/yauzl-promise": "2.1.0",
+    "typescript": "3.3.3"
+  }
+}

packages/now-layer-node/src/index.ts

@@ -0,0 +1,37 @@
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { glob, Files } from '@now/build-utils';
+import { mkdir, remove, pathExists } from 'fs-extra';
+import { install } from './install';
+
+interface BuildLayerConfig {
+  runtimeVersion: string;
+  platform: string;
+  arch: string;
+}
+
+interface BuildLayerResult {
+  files: Files;
+  entrypoint: string;
+}
+
+export async function buildLayer({
+  runtimeVersion,
+  platform,
+  arch,
+}: BuildLayerConfig): Promise<BuildLayerResult> {
+  const dir = join(
+    tmpdir(),
+    `now-layer-node-${runtimeVersion}-${platform}-${arch}`
+  );
+  const exists = await pathExists(dir);
+  if (exists) {
+    await remove(dir);
+  }
+  await mkdir(dir);
+  const { entrypoint } = await install(dir, runtimeVersion, platform, arch);
+  const files = await glob('{bin/node,bin/node.exe,include/**}', {
+    cwd: dir,
+  });
+  return { files, entrypoint };
+}

packages/now-layer-node/src/install.ts

@@ -0,0 +1,68 @@
+import { basename, join } from 'path';
+import fetch from 'node-fetch';
+import { extract } from 'tar';
+import pipe from 'promisepipe';
+import { createWriteStream } from 'fs-extra';
+import { unzip, zipFromFile } from './unzip';
+
+export async function install(
+  dest: string,
+  version: string,
+  platform: string,
+  arch: string
+) {
+  const tarballUrl = getUrl(version, platform, arch);
+  console.log('Downloading from ' + tarballUrl);
+  console.log('Downloading to ' + dest);
+  const res = await fetch(tarballUrl);
+  if (!res.ok) {
+    throw new Error(`HTTP request failed: ${res.status}`);
+  }
+  let entrypoint: string;
+  if (platform === 'win32') {
+    // Put it in the `bin` dir for consistency with the tarballs
+    const finalDest = join(dest, 'bin');
+    const zipName = basename(tarballUrl);
+    const zipPath = join(dest, zipName);
+
+    await pipe(
+      res.body,
+      createWriteStream(zipPath)
+    );
+
+    const zipFile = await zipFromFile(zipPath);
+    await unzip(zipFile, finalDest, { strip: 1 });
+    entrypoint = join('bin', 'node.exe');
+  } else {
+    const extractStream = extract({ strip: 1, C: dest });
+    if (!extractStream.destroy) {
+      // If there is an error in promisepipe,
+      // it expects a destroy method
+      extractStream.destroy = () => {};
+    }
+    await pipe(
+      res.body,
+      extractStream
+    );
+    entrypoint = join('bin', 'node');
+  }
+
+  return { entrypoint };
+}
+
+export function getUrl(
+  version: string,
+  platform: string = process.platform,
+  arch: string = process.arch
+): string {
+  let ext: string;
+  let plat: string;
+  if (platform === 'win32') {
+    ext = 'zip';
+    plat = 'win';
+  } else {
+    ext = 'tar.gz';
+    plat = platform;
+  }
+  return `https://nodejs.org/dist/v${version}/node-v${version}-${plat}-${arch}.${ext}`;
+}

packages/now-layer-node/src/unzip.ts

@@ -0,0 +1,96 @@
+import { tmpdir } from 'os';
+import pipe from 'promisepipe';
+import { dirname, join } from 'path';
+import { createWriteStream, mkdirp, symlink, unlink } from 'fs-extra';
+import streamToPromise from 'stream-to-promise';
+import {
+  Entry,
+  ZipFile,
+  open as zipFromFile,
+  fromBuffer as zipFromBuffer,
+} from 'yauzl-promise';
+
+export { zipFromFile, zipFromBuffer, ZipFile };
+
+export async function unzipToTemp(
+  data: Buffer | string,
+  tmpDir: string = tmpdir()
+): Promise<string> {
+  const dir = join(
+    tmpDir,
+    `zeit-fun-${Math.random()
+      .toString(16)
+      .substring(2)}`
+  );
+  let zip: ZipFile;
+  if (Buffer.isBuffer(data)) {
+    zip = await zipFromBuffer(data);
+  } else {
+    zip = await zipFromFile(data);
+  }
+  await unzip(zip, dir);
+  await zip.close();
+  return dir;
+}
+
+interface UnzipOptions {
+  strip?: number;
+}
+
+export async function unzip(
+  zipFile: ZipFile,
+  dir: string,
+  opts: UnzipOptions = {}
+): Promise<void> {
+  let entry: Entry;
+  const strip = opts.strip || 0;
+  while ((entry = await zipFile.readEntry()) !== null) {
+    const fileName =
+      strip === 0
+        ? entry.fileName
+        : entry.fileName
+            .split('/')
+            .slice(strip)
+            .join('/');
+    const destPath = join(dir, fileName);
+    if (/\/$/.test(entry.fileName)) {
+      await mkdirp(destPath);
+    } else {
+      const [entryStream] = await Promise.all([
+        entry.openReadStream(),
+        // ensure parent directory exists
+        mkdirp(dirname(destPath)),
+      ]);
+      const mode = entry.externalFileAttributes >>> 16;
+      if (isSymbolicLink(mode)) {
+        const linkDest = String(await streamToPromise(entryStream));
+        await symlink(linkDest, destPath);
+      } else {
+        const octal = mode & 4095 /* 07777 */;
+        const modeOctal = ('0000' + octal.toString(8)).slice(-4);
+        const modeVal = parseInt(modeOctal, 8);
+        try {
+          await unlink(destPath);
+        } catch (err) {
+          if (err.code !== 'ENOENT') {
+            throw err;
+          }
+        }
+        const destStream = createWriteStream(destPath, {
+          mode: modeVal,
+        });
+        await pipe(
+          entryStream,
+          destStream
+        );
+      }
+    }
+  }
+}
+
+const S_IFMT = 61440; /* 0170000 type of file */
+const S_IFLNK = 40960; /* 0120000 symbolic link */
+
+export function isSymbolicLink(mode: number): boolean {
+  return (mode & S_IFMT) === S_IFLNK;
+}

packages/now-layer-node/test/test.js

@@ -0,0 +1,54 @@
+/* global jest, expect, it */
+jest.setTimeout(30 * 1000);
+const { buildLayer } = require('../');
+
+describe('buildLayer', () => {
+  it('should get node 10 and metadata for windows', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '10.16.0',
+      platform: 'win32',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(names.size).toBeGreaterThan(0);
+    expect(entrypoint).toBe('bin/node.exe');
+    expect(names.has('bin/node.exe')).toBeTruthy();
+    expect(names.has('bin/npm.cmd')).toBeFalsy();
+    expect(names.has('bin/npx.cmd')).toBeFalsy();
+    expect(names.has('bin/node_modules')).toBeFalsy();
+  });
+
+  it('should get node 10 and metadata for macos', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '10.16.0',
+      platform: 'darwin',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(names.size).toBeGreaterThan(0);
+    expect(entrypoint).toBe('bin/node');
+    expect(names.has('bin/node')).toBeTruthy();
+    expect(names.has('bin/npm')).toBeFalsy();
+    expect(names.has('bin/npx')).toBeFalsy();
+    expect(names.has('lib/node_modules')).toBeFalsy();
+  });
+
+  it('should get node 10 and metadata for linux', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '10.16.0',
+      platform: 'linux',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(names.size).toBeGreaterThan(0);
+    expect(entrypoint).toBe('bin/node');
+    expect(names.has('bin/node')).toBeTruthy();
+    expect(names.has('include/node/node.h')).toBeTruthy();
+    expect(names.has('bin/npm')).toBeFalsy();
+    expect(names.has('bin/npx')).toBeFalsy();
+    expect(names.has('lib/node_modules')).toBeFalsy();
+  });
+});

packages/now-layer-node/tsconfig.json

@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "declaration": false,
+    "esModuleInterop": true,
+    "lib": ["esnext"],
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "noEmitOnError": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "outDir": "dist",
+    "types": ["node"],
+    "strict": true,
+    "target": "esnext"
+  }
+}

packages/now-layer-node/types/promisepipe.ts

@@ -0,0 +1,4 @@
+declare module 'promisepipe' {
+  import { Stream } from 'stream';
+  export default function pipe(...args: Stream[]): Promise<void>;
+}

packages/now-layer-node/types/stream-to-promise.ts

@@ -0,0 +1,6 @@
+declare module 'stream-to-promise' {
+  import { Stream } from 'stream';
+  export default function streamToPromise(
+    stream: NodeJS.ReadableStream
+  ): Promise<string>;
+}

packages/now-layer-npm/.gitignore

@@ -0,0 +1 @@
+/dist

packages/now-layer-npm/package.json

@@ -0,0 +1,29 @@
+{
+  "name": "@now/layer-npm",
+  "version": "0.0.2",
+  "main": "./dist/src/index",
+  "license": "MIT",
+  "files": [
+    "dist"
+  ],
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/zeit/now-builders.git",
+    "directory": "packages/now-layer-npm"
+  },
+  "scripts": {
+    "build": "tsc",
+    "test": "tsc && jest",
+    "prepublishOnly": "tsc"
+  },
+  "dependencies": {
+    "fs-extra": "7.0.1",
+    "node-fetch": "2.6.0",
+    "promisepipe": "3.0.0",
+    "tar": "4.4.6"
+  },
+  "devDependencies": {
+    "@types/tar": "4.0.0",
+    "typescript": "3.3.3"
+  }
+}

packages/now-layer-npm/src/index.ts

@@ -0,0 +1,37 @@
+import { tmpdir } from 'os';
+import { join } from 'path';
+import { glob, Files } from '@now/build-utils';
+import { mkdir, remove, pathExists } from 'fs-extra';
+import { install } from './install';
+
+interface BuildLayerConfig {
+  runtimeVersion: string;
+  platform: string;
+  arch: string;
+}
+
+interface BuildLayerResult {
+  files: Files;
+  entrypoint: string;
+}
+
+export async function buildLayer({
+  runtimeVersion,
+  platform,
+  arch,
+}: BuildLayerConfig): Promise<BuildLayerResult> {
+  const dir = join(
+    tmpdir(),
+    `now-layer-npm-${runtimeVersion}-${platform}-${arch}`
+  );
+  const exists = await pathExists(dir);
+  if (exists) {
+    await remove(dir);
+  }
+  await mkdir(dir);
+  const { entrypoint } = await install(dir, runtimeVersion);
+  const files = await glob('{bin/**,lib/**,node_modules/**}', {
+    cwd: dir,
+  });
+  return { files, entrypoint };
+}

packages/now-layer-npm/src/install.ts

@@ -0,0 +1,29 @@
+import { join } from 'path';
+import fetch from 'node-fetch';
+import { extract } from 'tar';
+import pipe from 'promisepipe';
+
+export async function install(dest: string, version: string) {
+  const tarballUrl = `https://registry.npmjs.org/npm/-/npm-${version}.tgz`;
+  console.log('Downloading from ' + tarballUrl);
+  console.log('Downloading to ' + dest);
+  const res = await fetch(tarballUrl);
+  if (!res.ok) {
+    throw new Error(`HTTP request failed: ${res.status}`);
+  }
+  const extractStream = extract({ strip: 1, C: dest });
+  if (!extractStream.destroy) {
+    // If there is an error in promisepipe,
+    // it expects a destroy method
+    extractStream.destroy = () => {};
+  }
+  await pipe(
+    res.body,
+    extractStream
+  );
+
+  const pathToManifest = join(dest, 'package.json');
+  const manifest = require(pathToManifest);
+  const entrypoint = manifest.bin.npm;
+  return { entrypoint };
+}

packages/now-layer-npm/test/test.js

@@ -0,0 +1,50 @@
+/* global jest, expect, it */
+jest.setTimeout(30 * 1000);
+const { buildLayer } = require('../');
+
+describe('buildLayer', () => {
+  it('should get npm 6 but not npm for windows', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '6.9.0',
+      platform: 'win32',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(entrypoint).toBe('./bin/npm-cli.js');
+    expect(names.size).toBeGreaterThan(0);
+    expect(names.has('bin/npm.cmd')).toBeTruthy();
+    expect(names.has('bin/npx.cmd')).toBeTruthy();
+    expect(names.has('README.md')).toBeFalsy();
+  });
+
+  it('should get npm 6 but not npm for macos', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '6.9.0',
+      platform: 'darwin',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(entrypoint).toBe('./bin/npm-cli.js');
+    expect(names.size).toBeGreaterThan(0);
+    expect(names.has('bin/npm')).toBeTruthy();
+    expect(names.has('bin/npx')).toBeTruthy();
+    expect(names.has('README.md')).toBeFalsy();
+  });
+
+  it('should get npm 6 but not npm for linux', async () => {
+    const { files, entrypoint } = await buildLayer({
+      runtimeVersion: '6.9.0',
+      platform: 'linux',
+      arch: 'x64',
+    });
+    const names = new Set(Object.keys(files));
+    expect(names).toBeTruthy();
+    expect(entrypoint).toBe('./bin/npm-cli.js');
+    expect(names.size).toBeGreaterThan(0);
+    expect(names.has('bin/npm')).toBeTruthy();
+    expect(names.has('bin/npx')).toBeTruthy();
+    expect(names.has('README.md')).toBeFalsy();
+  });
+});

packages/now-layer-npm/tsconfig.json

@@ -0,0 +1,18 @@
+{
+  "compilerOptions": {
+    "declaration": false,
+    "esModuleInterop": true,
+    "lib": ["esnext"],
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "noEmitOnError": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "outDir": "dist",
+    "types": ["node"],
+    "strict": true,
+    "target": "esnext"
+  }
+}

packages/now-layer-npm/types/promisepipe.ts

@@ -0,0 +1,4 @@
+declare module 'promisepipe' {
+  import { Stream } from 'stream';
+  export default function pipe(...args: Stream[]): Promise<void>;
+}

packages/now-layer-yarn/.gitignore

@@ -0,0 +1 @@
+/dist