BREAKING: Ignore 'functions' directory in a Firebase project without a functions config in firebase.json (#6555)

Historically, Firebase CLI reserved directory named `functions` inside a Firebase project directory for use by Cloud Functions for Firebase. This meant that if `functions` directory exists, it was assumed to hold CF3 source code.

However, we recognize that there are valid use case for using `functions` directory name, especially in monorepo-like setups.

With this change, Firebase CLI will only reserve `functions` directory when there is a `functions` configuration entry in firebase.json that does not specify the `source` directory.

This change will be released in the next breaking change of the Firebase CLI (v13).

Fixes #6450

Author: taeold

scripts/functions-discover-tests/fixtures/esm/firebase.json

@@ -1 +1,3 @@
-{}
+{
+  "functions": {}
+}

scripts/functions-discover-tests/fixtures/pnpm/firebase.json

@@ -1 +1,3 @@
-{}
+{
+  "functions": {}
+}

scripts/functions-discover-tests/fixtures/simple/firebase.json

@@ -1 +1,3 @@
-{}
+{
+  "functions": {}
+}

src/config.ts

@@ -76,15 +76,17 @@ export class Config {
       }
     });
 
-    // Inject default functions config and source if missing.
-    if (this.projectDir && fsutils.dirExistsSync(this.path(Config.DEFAULT_FUNCTIONS_SOURCE))) {
-      if (Array.isArray(this.get("functions"))) {
-        if (!this.get("functions.[0].source")) {
-          this.set("functions.[0].source", Config.DEFAULT_FUNCTIONS_SOURCE);
-        }
-      } else {
-        if (!this.get("functions.source")) {
-          this.set("functions.source", Config.DEFAULT_FUNCTIONS_SOURCE);
+    // Inject default functions source if missing.
+    if (this.get("functions")) {
+      if (this.projectDir && fsutils.dirExistsSync(this.path(Config.DEFAULT_FUNCTIONS_SOURCE))) {
+        if (Array.isArray(this.get("functions"))) {
+          if (!this.get("functions.[0].source")) {
+            this.set("functions.[0].source", Config.DEFAULT_FUNCTIONS_SOURCE);
+          }
+        } else {
+          if (!this.get("functions.source")) {
+            this.set("functions.source", Config.DEFAULT_FUNCTIONS_SOURCE);
+          }
         }
       }
     }