Add initial vercel-plugin-middleware (#6892)

* Add initial `vercel-plugin-middleware`

* Ignore `entries.js` from ESLint

* Add `runDevMiddleware()` stub

* Add test

* Add support for "_middleware.{js,ts}" to `vercel dev` (#6880)

* Add websandbox from next.js codebase.

* Use node-fetch instead of next's polyfilled fetch.

* Handle middleware rewrites.

* Add response, headers, and request to websandbox context.

* Move websandbox dependency to middleware plugin.

* Add integration tests, update websandbox to support ts files and json imports.

* commit yarn.lock changes after rebasing

* Clean up left over console.logs, fix some tsc issues, and rebase issue.

* Fix failing test and eslint.

* Fix middleware test on windows.

* [examples] Update Vercel Next.js example template to 12.0.1 (#6905)

* Mark the Plugins as external to CLI's ncc build

* [cli] Improve tracing in vc build (#6898)

* [cli] Fix tracing for `vc build`

* Ignore object when there are no changes

* Make Next < 12 work with FS API w/ nft

* Update packages/cli/src/commands/build.ts

Co-authored-by: Nathan Rajlich <n@n8.io>

* Document how Next.js processing works in build

* [cli] Fix static assets (#6906)

* Make sure output path is .next

* Fix up require-server-files for processing

* Fix typo

* Move static

* Update static rename

Co-authored-by: Andy Bitz <artzbitz@gmail.com>
Co-authored-by: Nathan Rajlich <n@n8.io>
Co-authored-by: Andy <AndyBitz@users.noreply.github.com>

* Publish Canary

 - vercel@23.1.3-canary.17
 - @vercel/client@10.2.3-canary.15
 - @vercel/static-config@0.0.1-canary.0

* [cli] Ignore `.env` and `.gitignore` in "vc build" (#6910)

* Publish Canary

 - vercel@23.1.3-canary.18

* Pass workPath to plugins.

The new plugin architecture doesn't pass a full BuildOptions object, previous
to this commit it wasn't passing any options at all. I've added workingPath to
support running dev/build from directories other than the project root.

* Remove error state when package.json exists, but no build script

This allows vercel build to continue working for projects that are not using
frameworks, but use package.json to manage dependencies.

* Fix types, pull in middleware header fix from next.js

Next js PR w/ the header fix:
https://github.com/vercel/next.js/pull/30560

* Fix missing entries file for vc build.

* Update call signature of middleware when using vc build.

Co-authored-by: Drew Bredvick <dbredvick@gmail.com>
Co-authored-by: Nathan Rajlich <n@n8.io>
Co-authored-by: Jared Palmer <jared@jaredpalmer.com>
Co-authored-by: Andy Bitz <artzbitz@gmail.com>
Co-authored-by: Andy <AndyBitz@users.noreply.github.com>

Co-authored-by: Gary Borton <gdborton@gmail.com>
Co-authored-by: Drew Bredvick <dbredvick@gmail.com>
Co-authored-by: Jared Palmer <jared@jaredpalmer.com>
Co-authored-by: Andy Bitz <artzbitz@gmail.com>
Co-authored-by: Andy <AndyBitz@users.noreply.github.com>

packages/cli/src/util/dev/server.ts

@@ -22,6 +22,8 @@ import deepEqual from 'fast-deep-equal';
 import which from 'which';
 import npa from 'npm-package-arg';
 
+import { runDevMiddleware } from 'vercel-plugin-middleware';
+
 import { getVercelIgnore, fileNameSymbol } from '@vercel/client';
 import {
   getTransformedRoutes,
@@ -1416,6 +1418,26 @@ export default class DevServer {
     let prevUrl = req.url;
     let prevHeaders: HttpHeadersConfig = {};
 
+    const middlewareResult = await runDevMiddleware(req, res, this.cwd);
+
+    if (middlewareResult) {
+      if (middlewareResult.finished) {
+        return;
+      }
+
+      if (middlewareResult.pathname) {
+        const origUrl = url.parse(req.url || '/', true);
+        origUrl.pathname = middlewareResult.pathname;
+        prevUrl = url.format(origUrl);
+      }
+      if (middlewareResult.query && prevUrl) {
+        const origUrl = url.parse(req.url || '/', true);
+        delete origUrl.search;
+        Object.assign(origUrl.query, middlewareResult.query);
+        prevUrl = url.format(origUrl);
+      }
+    }
+
     for (const phase of phases) {
       statusCode = undefined;