Fix Vercel build (#5830)

Author: schmidt-sebastian

.changeset/eight-cows-push.md

@@ -0,0 +1,5 @@
+---
+"@firebase/firestore": patch
+---
+
+Fix Proto loading for Vercel/Next.js.

packages/firestore/rollup.config.js

@@ -23,6 +23,7 @@ import replace from 'rollup-plugin-replace';
 import { terser } from 'rollup-plugin-terser';
 import typescriptPlugin from 'rollup-plugin-typescript2';
 import tmp from 'tmp';
+import { basename } from 'path';
 import typescript from 'typescript';
 
 import { generateBuildTargetReplaceConfig } from '../../scripts/build/rollup_replace_build_target';
@@ -31,16 +32,34 @@ import pkg from './package.json';
 
 const util = require('./rollup.shared');
 
-// Customize how import.meta.url is polyfilled in cjs nodejs build. We use it to be able to use require() in esm.
-// It only generates the nodejs version of the polyfill, as opposed to the default polyfill which
-// supports both browser and nodejs. The browser support is unnecessary and doesn't work well with Jest. See https://github.com/firebase/firebase-js-sdk/issues/5687
-function importMetaUrlPolyfillPlugin() {
+// Customize how import.meta.url is polyfilled in cjs nodejs build. We use it to
+// be able to use require() in esm. It only generates the nodejs version of the
+// polyfill, as opposed to the default polyfill which supports both browser and
+// nodejs. The browser support doesn't work well with Jest.
+// See https://github.com/firebase/firebase-js-sdk/issues/5687
+// Although this is a cjs Node build and shouldn't require the browser option,
+// Vercel apps using this break on deployment, but work in local development.
+// See https://github.com/firebase/firebase-js-sdk/issues/5823
+function importMetaUrlPolyfillPlugin(filename) {
   return {
     name: 'import-meta-url-current-module',
     resolveImportMeta(property, { moduleId }) {
       if (property === 'url') {
-        // copied from rollup output
-        return `new (require('url').URL)('file:' + __filename).href`;
+        // Added a check for Jest (see issue 5687 linked above)
+        // See https://jestjs.io/docs/environment-variables - apparently
+        // these are not always both set.
+        const JEST_CHECK =
+          `typeof process !== 'undefined' && process.env !== undefined` +
+          ` && (process.env.JEST_WORKER_ID !== undefined || ` +
+          `process.env.NODE_ENV === 'test')`;
+        // Copied from rollup output
+        return (
+          `((typeof document === 'undefined' || (${JEST_CHECK})) ?` +
+          ` new (require('url').URL)` +
+          `('file:' + __filename).href : (document.currentScript && ` +
+          `document.currentScript.src || new URL('${filename}', ` +
+          `document.baseURI).href))`
+        );
       }
       return null;
     }
@@ -124,7 +143,7 @@ const allBuilds = [
     plugins: [
       ...util.es2017ToEs5Plugins(/* mangled= */ false),
       replace(generateBuildTargetReplaceConfig('cjs', 2017)),
-      importMetaUrlPolyfillPlugin()
+      importMetaUrlPolyfillPlugin(basename(pkg.main))
     ],
     external: util.resolveNodeExterns,
     treeshake: {