Inject FIREBASE_CONFIG environment variable for scripts executed vi…

…a emulators:exec command. (#5544)

As discussed in #5536 (comment), we learned that old versions of Firebase Functions SDK always made `process.env.FIREBASE_CONFIG` available to the underlying script that imported the Firebase Functions SDK.

While making `process.env.FIREBASE_CONFIG` available wasn't intentional, we'll consider this a case of [Hyrum's Law](https://www.hyrumslaw.com/) and will try our best to fix the regression by making `process.env.FIREBASE_CONFIG` environment variable available if not set in the parent process.

Fixes #5536

CHANGELOG.md

@@ -2,3 +2,4 @@
 - Fixes bug where passing `--port` flag in `functions:shell` does not set which port to emulate functions (#5521)
 - Improve error message during deploy when given invalid hosting rewrite rule (#5533)
 - Generate ESM-compatible SSR function for web frameworks (#5540)
+- Fix bug emulators:exec script didn't populate FIREBASE_CONFIG environment variable (#5544)

src/emulator/commandUtils.ts

@@ -329,6 +329,18 @@ async function runScript(script: string, extraEnv: Record<string, string>): Prom
   utils.logBullet(`Running script: ${clc.bold(script)}`);
 
   const env: NodeJS.ProcessEnv = { ...process.env, ...extraEnv };
+  // Hyrum's Law strikes here:
+  //   Scripts that imported older versions of Firebase Functions SDK accidentally made
+  //   the FIREBASE_CONFIG environment variable always available to the script.
+  //   Many users ended up depending on this behavior, so we conditionally inject the env var
+  //   if the FIREBASE_CONFIG env var isn't explicitly set in the parent process.
+  if (env.GCLOUD_PROJECT && !env.FIREBASE_CONFIG) {
+    env.FIREBASE_CONFIG = JSON.stringify({
+      projectId: env.GCLOUD_PROJECT,
+      storageBucket: `${env.GCLOUD_PROJECT}.appspot.com`,
+      databaseURL: `https://${env.GCLOUD_PROJECT}.firebaseio.com`,
+    });
+  }
 
   const emulatorInfos = EmulatorRegistry.listRunningWithInfo();
   setEnvVarsForEmulators(env, emulatorInfos);
@@ -448,7 +460,7 @@ const JAVA_HINT = "Please make sure Java is installed and on your system PATH.";
 /**
  * Return whether Java major verion is supported. Throws if Java not available.
  *
- * @returns Java major version (for Java >= 9) or -1 otherwise
+ * @return Java major version (for Java >= 9) or -1 otherwise
  */
 export async function checkJavaMajorVersion(): Promise<number> {
   return new Promise<string>((resolve, reject) => {
@@ -510,7 +522,7 @@ export async function checkJavaMajorVersion(): Promise<number> {
     });
   }).then((output) => {
     let versionInt = -1;
-    const match = output.match(JAVA_VERSION_REGEX);
+    const match = JAVA_VERSION_REGEX.exec(output);
     if (match) {
       const version = match[1];
       versionInt = parseInt(version, 10);