Fix Vercel build

Author: schmidt-sebastian

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 +32,21 @@ 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 is unnecessary and doesn't work well with Jest.
+// See https://github.com/firebase/firebase-js-sdk/issues/5687
+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`;
+        return "(typeof document === 'undefined' ? new (require('url').URL)"
+          + "('file:' + __filename).href : (document.currentScript && "
+          + `document.currentScript.src || new URL('${filename}', `
+          + "document.baseURI).href))";
       }
       return null;
     }
@@ -124,7 +130,7 @@ const allBuilds = [
     plugins: [
       ...util.es2017ToEs5Plugins(/* mangled= */ false),
       replace(generateBuildTargetReplaceConfig('cjs', 2017)),
-      importMetaUrlPolyfillPlugin()
+      importMetaUrlPolyfillPlugin(basename(pkg.main))
     ],
     external: util.resolveNodeExterns,
     treeshake: {