[python] Add discontinue date for Python 3.6 (#7709)

This PR does a few things:
- Changes the existing warning message for Python 3.6 to print a discontinue date
- Will automatically fail new Python 3.6 deployments created after that date
- Consolidates logic to make Python version selection work in a similar manner to Node.js version selection
- Changes tests from JS to TS

packages/python/jest.config.js

@@ -0,0 +1,5 @@
+/** @type {import('@ts-jest/dist/types').InitialOptionsTsJest} */
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+};

packages/python/package.json

@@ -15,11 +15,13 @@
   },
   "scripts": {
     "build": "node build",
-    "test-integration-once": "jest --env node --verbose --runInBand --bail",
+    "test-unit": "jest --env node --verbose --runInBand --bail test/unit.test.ts ",
+    "test-integration-once": "jest --env node --verbose --runInBand --bail test/integration.test.ts",
     "prepublishOnly": "node build"
   },
   "devDependencies": {
     "@types/execa": "^0.9.0",
+    "@types/jest": "27.0.1",
     "@vercel/build-utils": "2.15.2-canary.4",
     "@vercel/ncc": "0.24.0",
     "execa": "^1.0.0",

packages/python/src/index.ts

@@ -16,6 +16,7 @@ import {
   NowBuildError,
 } from '@vercel/build-utils';
 import { installRequirement, installRequirementsFile } from './install';
+import { getLatestPythonVersion, getSupportedPythonVersion } from './version';
 
 async function pipenvConvert(cmd: string, srcDir: string) {
   debug('Running pipfile2req...');
@@ -59,9 +60,7 @@ export const build = async ({
   meta = {},
   config,
 }: BuildOptions) => {
-  let pipPath = meta.isDev ? 'pip3' : 'pip3.9';
-  let pythonPath = meta.isDev ? 'python3' : 'python3.9';
-  let pythonRuntime = meta.isDev ? 'python3' : 'python3.9';
+  let pythonVersion = getLatestPythonVersion(meta);
 
   workPath = await downloadFilesInWorkPath({
     workPath,
@@ -91,8 +90,8 @@ export const build = async ({
   console.log('Installing required dependencies...');
 
   await installRequirement({
-    pythonPath,
-    pipPath,
+    pythonPath: pythonVersion.pythonPath,
+    pipPath: pythonVersion.pipPath,
     dependency: 'werkzeug',
     version: '1.0.1',
     workPath,
@@ -114,25 +113,10 @@ export const build = async ({
     try {
       const json = await readFile(join(pipfileLockDir, 'Pipfile.lock'), 'utf8');
       const obj = JSON.parse(json);
-      const version = obj?._meta?.requires?.python_version;
-      if (!meta.isDev) {
-        if (version === '3.6') {
-          pipPath = 'pip3.6';
-          pythonPath = 'python3.6';
-          pythonRuntime = 'python3.6';
-          console.warn(
-            `Warning: Python version "${version}" detected in Pipfile.lock will reach End-Of-Life December 2021. Please upgrade. http://vercel.link/python-version`
-          );
-        } else if (version === '3.9') {
-          pipPath = 'pip3.9';
-          pythonPath = 'python3.9';
-          pythonRuntime = 'python3.9';
-        } else {
-          console.warn(
-            `Warning: Invalid Python version "${version}" detected in Pipfile.lock will be ignored. http://vercel.link/python-version`
-          );
-        }
-      }
+      pythonVersion = getSupportedPythonVersion({
+        isDev: meta.isDev,
+        pipLockPythonVersion: obj?._meta?.requires?.python_version,
+      });
     } catch (err) {
       throw new NowBuildError({
         code: 'INVALID_PIPFILE_LOCK',
@@ -146,8 +130,8 @@ export const build = async ({
     // it into a separate folder.
     const tempDir = await getWriteableDirectory();
     await installRequirement({
-      pythonPath,
-      pipPath,
+      pythonPath: pythonVersion.pythonPath,
+      pipPath: pythonVersion.pipPath,
       dependency: 'pipfile-requirements',
       version: '0.3.0',
       workPath: tempDir,
@@ -169,8 +153,8 @@ export const build = async ({
     debug('Found local "requirements.txt"');
     const requirementsTxtPath = fsFiles[requirementsTxt].fsPath;
     await installRequirementsFile({
-      pythonPath,
-      pipPath,
+      pythonPath: pythonVersion.pythonPath,
+      pipPath: pythonVersion.pipPath,
       filePath: requirementsTxtPath,
       workPath,
       meta,
@@ -179,8 +163,8 @@ export const build = async ({
     debug('Found global "requirements.txt"');
     const requirementsTxtPath = fsFiles['requirements.txt'].fsPath;
     await installRequirementsFile({
-      pythonPath,
-      pipPath,
+      pythonPath: pythonVersion.pythonPath,
+      pipPath: pythonVersion.pipPath,
       filePath: requirementsTxtPath,
       workPath,
       meta,
@@ -205,9 +189,6 @@ export const build = async ({
 
   await writeFile(join(workPath, `${handlerPyFilename}.py`), handlerPyContents);
 
-  // Use the system-installed version of `python3` when running via `vercel dev`
-  const runtime = meta.isDev ? 'python3' : pythonRuntime;
-
   const globOptions: GlobOptions = {
     cwd: workPath,
     ignore:
@@ -219,7 +200,7 @@ export const build = async ({
   const lambda = await createLambda({
     files: await glob('**', globOptions),
     handler: `${handlerPyFilename}.vc_handler`,
-    runtime,
+    runtime: pythonVersion.runtime,
     environment: {},
   });
 

packages/python/src/version.ts

@@ -0,0 +1,95 @@
+import { NowBuildError } from '@vercel/build-utils';
+
+interface PythonVersion {
+  version: string;
+  pipPath: string;
+  pythonPath: string;
+  runtime: string;
+  discontinueDate?: Date;
+}
+
+// The order must be most recent first
+const allOptions: PythonVersion[] = [
+  {
+    version: '3.9',
+    pipPath: 'pip3.9',
+    pythonPath: 'python3.9',
+    runtime: 'python3.9',
+  },
+  {
+    version: '3.6',
+    pipPath: 'pip3.6',
+    pythonPath: 'python3.6',
+    runtime: 'python3.6',
+    discontinueDate: new Date('2022-07-18'),
+  },
+];
+
+const upstreamProvider =
+  'This change is the result of a decision made by an upstream infrastructure provider (AWS)';
+
+function getDevPythonVersion(): PythonVersion {
+  // Use the system-installed version of `python3` when running `vercel dev`
+  return {
+    version: '3',
+    pipPath: 'pip3',
+    pythonPath: 'python3',
+    runtime: 'python3',
+  };
+}
+export function getLatestPythonVersion({
+  isDev,
+}: {
+  isDev?: boolean;
+}): PythonVersion {
+  if (isDev) {
+    return getDevPythonVersion();
+  }
+  return allOptions[0];
+}
+
+export function getSupportedPythonVersion({
+  isDev,
+  pipLockPythonVersion,
+}: {
+  isDev?: boolean;
+  pipLockPythonVersion: string | undefined;
+}): PythonVersion {
+  if (isDev) {
+    return getDevPythonVersion();
+  }
+  let selection = getLatestPythonVersion({ isDev: false });
+
+  if (typeof pipLockPythonVersion === 'string') {
+    const found = allOptions.find(o => o.version === pipLockPythonVersion);
+    if (found) {
+      selection = found;
+    } else {
+      console.warn(
+        `Warning: Python version "${pipLockPythonVersion}" detected in Pipfile.lock is invalid and will be ignored. http://vercel.link/python-version`
+      );
+    }
+  }
+
+  if (isDiscontinued(selection)) {
+    throw new NowBuildError({
+      code: 'BUILD_UTILS_PYTHON_VERSION_DISCONTINUED',
+      link: 'http://vercel.link/python-version',
+      message: `Python version "${selection.version}" detected in Pipfile.lock is discontinued and must be upgraded. ${upstreamProvider}.`,
+    });
+  }
+
+  if (selection.discontinueDate) {
+    const d = selection.discontinueDate.toISOString().split('T')[0];
+    console.warn(
+      `Error: Python version "${selection.version}" detected in Pipfile.lock is deprecated. Deployments created on or after ${d} will fail to build. ${upstreamProvider}. http://vercel.link/python-version`
+    );
+  }
+
+  return selection;
+}
+
+function isDiscontinued({ discontinueDate }: PythonVersion): boolean {
+  const today = Date.now();
+  return discontinueDate !== undefined && discontinueDate.getTime() <= today;
+}

packages/python/test/fixtures/02-wsgi-pipenv/vercel.json

@@ -5,7 +5,7 @@
     {
       "path": "/",
       "mustContain": "wsgi:RANDOMNESS_PLACEHOLDER",
-      "logMustContain": "Warning: Python version \"3.6\" detected in Pipfile.lock will reach End-Of-Life December 2021. Please upgrade."
+      "logMustContain": "Python version \"3.6\" detected in Pipfile.lock is deprecated. Deployments created on or after 2022-07-18 will fail to build"
     }
   ]
 }

packages/python/test/fixtures/03-env-vars/vercel.json

@@ -8,7 +8,7 @@
     {
       "path": "/",
       "mustContain": "RANDOMNESS_PLACEHOLDER:env",
-      "logMustContain": "Warning: Python version \"3.6\" detected in Pipfile.lock will reach End-Of-Life December 2021. Please upgrade."
+      "logMustContain": "Python version \"3.6\" detected in Pipfile.lock is deprecated. Deployments created on or after 2022-07-18 will fail to build"
     }
   ]
 }

packages/python/test/fixtures/04-cowsay-pipfile/vercel.json

@@ -5,7 +5,7 @@
     {
       "path": "/",
       "mustContain": "pip:RANDOMNESS_PLACEHOLDER",
-      "logMustContain": "Warning: Invalid Python version \"3.7\" detected in Pipfile.lock will be ignored."
+      "logMustContain": "Python version \"3.7\" detected in Pipfile.lock is invalid and will be ignored."
     }
   ]
 }

packages/python/test/integration.test.ts

@@ -12,7 +12,7 @@ const {
 
 jest.setTimeout(4 * 60 * 1000);
 const buildUtilsUrl = '@canary';
-let builderUrl;
+let builderUrl: string;
 
 beforeAll(async () => {
   const builderPath = path.resolve(__dirname, '..');

packages/python/test/tsconfig.json

@@ -0,0 +1,4 @@
+{
+  "extends": "../tsconfig.json",
+  "include": ["*.test.ts"]
+}

packages/python/test/unit.test.ts

@@ -0,0 +1,75 @@
+import { getSupportedPythonVersion } from '../src/version';
+
+let warningMessages: string[];
+const originalConsoleWarn = console.warn;
+const realDateNow = Date.now.bind(global.Date);
+beforeEach(() => {
+  warningMessages = [];
+  console.warn = m => {
+    warningMessages.push(m);
+  };
+});
+
+afterEach(() => {
+  console.warn = originalConsoleWarn;
+  global.Date.now = realDateNow;
+});
+
+it('should only match supported versions, otherwise throw an error', async () => {
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.9' })
+  ).toHaveProperty('runtime', 'python3.9');
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.6' })
+  ).toHaveProperty('runtime', 'python3.6');
+});
+
+it('should ignore minor version in vercel dev', async () => {
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.9', isDev: true })
+  ).toHaveProperty('runtime', 'python3');
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.6', isDev: true })
+  ).toHaveProperty('runtime', 'python3');
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '999', isDev: true })
+  ).toHaveProperty('runtime', 'python3');
+  expect(warningMessages).toStrictEqual([]);
+});
+
+it('should select latest version when no Piplock detected', async () => {
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: undefined })
+  ).toHaveProperty('runtime', 'python3.9');
+  expect(warningMessages).toStrictEqual([]);
+});
+
+it('should select latest version and warn when invalid Piplock detected', async () => {
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '999' })
+  ).toHaveProperty('runtime', 'python3.9');
+  expect(warningMessages).toStrictEqual([
+    'Warning: Python version "999" detected in Pipfile.lock is invalid and will be ignored. http://vercel.link/python-version',
+  ]);
+});
+
+it('should throw for discontinued versions', async () => {
+  global.Date.now = () => new Date('2022-07-31').getTime();
+  expect(() =>
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.6' })
+  ).toThrow(
+    'Python version "3.6" detected in Pipfile.lock is discontinued and must be upgraded. This change is the result of a decision made by an upstream infrastructure provider (AWS).'
+  );
+  expect(warningMessages).toStrictEqual([]);
+});
+
+it('should warn for deprecated versions, soon to be discontinued', async () => {
+  global.Date.now = () => new Date('2021-07-01').getTime();
+
+  expect(
+    getSupportedPythonVersion({ pipLockPythonVersion: '3.6' })
+  ).toHaveProperty('runtime', 'python3.6');
+  expect(warningMessages).toStrictEqual([
+    'Error: Python version "3.6" detected in Pipfile.lock is deprecated. Deployments created on or after 2022-07-18 will fail to build. This change is the result of a decision made by an upstream infrastructure provider (AWS). http://vercel.link/python-version',
+  ]);
+});

packages/python/tsconfig.json

@@ -11,8 +11,10 @@
     "noUnusedLocals": true,
     "noUnusedParameters": true,
     "outDir": "dist",
-    "types": ["node"],
+    "types": ["node", "jest"],
     "strict": true,
     "target": "es2018"
-  }
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules"]
 }