feat(cli): add --firebase-out flag for custom firebase.json path

packages/flutterfire_cli/lib/src/commands/base.dart

@@ -20,6 +20,7 @@ import 'dart:io';
 import 'package:args/args.dart';
 import 'package:args/command_runner.dart';
 import 'package:cli_util/cli_logging.dart';
+import 'package:path/path.dart' as path;
 
 import '../common/strings.dart';
 import '../common/utils.dart';
@@ -42,6 +43,25 @@ abstract class FlutterFireCommand extends Command<void> {
     return argResults!['account'] as String?;
   }
 
+  /// Resolves the path to the `firebase.json` file.
+  ///
+  /// If a [customPath] is provided, it is returned directly if it is absolute.
+  /// If it is relative, it is resolved relative to the project root (`FlutterApp.package.path`).
+  /// If no [customPath] is provided, it defaults to `firebase.json` in the project root.
+  String resolveFirebaseJsonPath(String? customPath) {
+    if (customPath != null) {
+      // If a custom path was provided, check if it is relative.
+      if (path.isRelative(customPath)) {
+        // Resolve relative paths relative to the project root to ensure consistent behavior.
+        return path.join(flutterApp!.package.path, customPath);
+      }
+      // Use absolute paths as provided.
+      return customPath;
+    }
+    // Default to the standard firebase.json in the project root if no custom path is specified.
+    return path.join(flutterApp!.package.path, 'firebase.json');
+  }
+
   void setupDefaultFirebaseCliOptions() {
     argParser.addOption(
       'project',

packages/flutterfire_cli/lib/src/commands/config.dart

@@ -18,7 +18,6 @@
 import 'dart:io';
 
 import 'package:ansi_styles/ansi_styles.dart';
-import 'package:path/path.dart' as path;
 
 import '../common/global.dart';
 import '../common/inputs.dart';
@@ -188,6 +187,12 @@ class ConfigCommand extends FlutterFireCommand {
           'Where to write the `google-services.json` file to be written for android platform. Useful for different flavors',
     );
 
+    argParser.addOption(
+      kFirebaseOutFlag,
+      valueHelp: 'filePath',
+      help: 'The output file path of the `firebase.json` file that will be generated or updated.',
+    );
+
     argParser.addFlag(
       kOverwriteFirebaseOptionsFlag,
       abbr: 'f',
@@ -345,6 +350,10 @@ class ConfigCommand extends FlutterFireCommand {
     return argResults!['out'] as String;
   }
 
+  String get firebaseJsonPath {
+    return resolveFirebaseJsonPath(argResults![kFirebaseOutFlag] as String?);
+  }
+
   bool get overwriteFirebaseOptions {
     if (argResults!['overwrite-firebase-options'] == null) {
       return false;
@@ -536,8 +545,6 @@ class ConfigCommand extends FlutterFireCommand {
   }
 
   Future<bool> checkIfUserRequiresReconfigure() async {
-    final firebaseJsonPath =
-        path.join(flutterApp!.package.path, 'firebase.json');
     final file = File(firebaseJsonPath);
 
     if (file.existsSync()) {
@@ -550,7 +557,7 @@ class ConfigCommand extends FlutterFireCommand {
             );
 
         if (reuseFirebaseJsonValues) {
-          final reconfigure = Reconfigure(flutterApp, token: testAccessToken);
+          final reconfigure = Reconfigure(flutterApp, token: testAccessToken, firebaseJsonPath: firebaseJsonPath);
           reconfigure.logger = logger;
           await reconfigure.run();
           return true;
@@ -705,12 +712,11 @@ class ConfigCommand extends FlutterFireCommand {
         firebaseJsonWrites.add(firebaseJsonWrite);
       }
 
-      // 5. Writes for "firebase.json" file in root of project
+      // 5. Writes for "firebase.json" file
       if (firebaseJsonWrites.isNotEmpty) {
         await writeToFirebaseJson(
           listOfWrites: firebaseJsonWrites,
-          firebaseJsonPath:
-              path.join(flutterApp!.package.path, 'firebase.json'),
+          firebaseJsonPath: firebaseJsonPath,
         );
       }
 

packages/flutterfire_cli/lib/src/commands/reconfigure.dart

@@ -56,18 +56,27 @@ class ConfigFileWrite {
 }
 
 class Reconfigure extends FlutterFireCommand {
-  Reconfigure(FlutterApp? flutterApp, {String? token}) : super(flutterApp) {
+  Reconfigure(FlutterApp? flutterApp, {String? token, String? firebaseJsonPath})
+      : super(flutterApp) {
     setupDefaultFirebaseCliOptions();
     _accessToken = token;
+    _firebaseJsonPath = firebaseJsonPath;
     argParser.addOption(
       'ci-access-token',
       valueHelp: 'ciAccessToken',
       hide: true,
       help:
           'Set the access token for making Firebase API requests. Required for CI environment.',
     );
+    argParser.addOption(
+      kFirebaseOutFlag,
+      valueHelp: 'filePath',
+      help: 'The path to the `firebase.json` file that will be used for reconfiguration.',
+    );
   }
 
+  String? _firebaseJsonPath;
+
   @override
   final String description =
       'Updates the configurations for all build variants included in the "firebase.json" added by running `flutterfire configure`.';
@@ -378,12 +387,12 @@ class Reconfigure extends FlutterFireCommand {
   Future<void> run() async {
     try {
       commandRequiresFlutterApp();
-      final firebaseJson = File(
-        path.join(
-          flutterApp!.package.path,
-          'firebase.json',
-        ),
-      );
+      final customPath =
+          argResults != null ? argResults![kFirebaseOutFlag] as String? : null;
+      // Determine the raw path, prioritizing the programmatic path passed from the configure command.
+      final rawPath = _firebaseJsonPath ?? customPath;
+
+      final firebaseJson = File(resolveFirebaseJsonPath(rawPath));
 
       if (!firebaseJson.existsSync()) {
         throw Exception(

packages/flutterfire_cli/lib/src/common/utils.dart

@@ -79,6 +79,7 @@ const String kMacosTargetFlag = 'macos-target';
 const String kIosOutFlag = 'ios-out';
 const String kMacosOutFlag = 'macos-out';
 const String kAndroidOutFlag = 'android-out';
+const String kFirebaseOutFlag = 'firebase-out';
 const String kOverwriteFirebaseOptionsFlag = 'overwrite-firebase-options';
 const String kTestAccessTokenFlag = 'test-access-token';
 

packages/flutterfire_cli/test/configure_test.dart

@@ -1740,4 +1740,52 @@ void main() {
       Duration(minutes: 3),
     ),
   );
+
+  test('flutterfire configure: --firebase-out flag should dictate where firebase.json is written', () async {
+    // Install flutterfire_cli from local path
+    final installDevDependency = Process.runSync(
+      'flutter',
+      [
+        'pub',
+        'add',
+        '--dev',
+        'flutterfire_cli',
+        '--path=${Directory.current.path}',
+      ],
+      workingDirectory: projectPath,
+    );
+
+    if (installDevDependency.exitCode != 0) {
+      fail(installDevDependency.stderr as String);
+    }
+
+    const customFirebaseJsonPath = 'custom/firebase.json';
+    final result = Process.runSync(
+      'dart',
+      [
+        'run',
+        'flutterfire_cli:flutterfire',
+        'configure',
+        '--yes',
+        '--project=$firebaseProjectId',
+        '--platforms=android',
+        '--firebase-out=$customFirebaseJsonPath',
+      ],
+      workingDirectory: projectPath,
+      runInShell: true,
+    );
+
+    if (result.exitCode != 0) {
+      fail(result.stderr as String);
+    }
+
+    // check custom "firebase.json" was created and has correct content
+    final firebaseJsonFile = p.join(projectPath!, 'custom', 'firebase.json');
+    expect(File(firebaseJsonFile).existsSync(), true);
+
+    final firebaseJsonFileContent = await File(firebaseJsonFile).readAsString();
+    final decodedFirebaseJson = jsonDecode(firebaseJsonFileContent) as Map<String, dynamic>;
+
+    expect(decodedFirebaseJson[kFlutter], isNotNull);
+  });
 }

packages/flutterfire_cli/test/reconfigure_test.dart

@@ -393,4 +393,77 @@ void main() {
       Duration(minutes: 2),
     ),
   );
+
+  test(
+    'flutterfire reconfigure: should use custom firebase.json path specified by --firebase-out',
+    () async {
+      const customFirebaseJsonPath = 'custom/firebase.json';
+      final scriptPath = p.join(Directory.current.path, 'bin', 'flutterfire.dart');
+
+      // 1. Run "flutterfire configure" with custom output path
+      final result = Process.runSync(
+        'dart',
+        [
+          scriptPath,
+          'configure',
+          '--yes',
+          '--platforms=android',
+          '--project=$firebaseProjectId',
+          '--firebase-out=$customFirebaseJsonPath',
+        ],
+        workingDirectory: projectPath,
+        runInShell: true,
+      );
+
+      if (result.exitCode != 0) {
+        fail(result.stderr);
+      }
+
+      // Verify custom file exists
+      final customFile = File(p.join(projectPath!, 'custom', 'firebase.json'));
+      expect(customFile.existsSync(), true);
+
+      // Delete generated files to force reconfigure to do work
+      final firebaseOptionsPath = p.join(projectPath!, 'lib', 'firebase_options.dart');
+      final androidServiceFilePath = p.join(
+        projectPath!,
+        'android',
+        'app',
+        androidServiceFileName,
+      );
+
+      if (File(firebaseOptionsPath).existsSync()) {
+        await File(firebaseOptionsPath).delete();
+      }
+      if (File(androidServiceFilePath).existsSync()) {
+        await File(androidServiceFilePath).delete();
+      }
+
+      final accessToken = await generateAccessTokenCI();
+
+      // 2. Run "flutterfire reconfigure" pointing to the custom path
+      final result2 = Process.runSync(
+        'dart',
+        [
+          scriptPath,
+          'reconfigure',
+          '--firebase-out=$customFirebaseJsonPath',
+          if (accessToken != null) '--ci-access-token=$accessToken',
+        ],
+        workingDirectory: projectPath,
+        runInShell: true,
+      );
+
+      if (result2.exitCode != 0) {
+        fail(result2.stderr);
+      }
+
+      // Check the files have been recreated
+      expect(File(firebaseOptionsPath).existsSync(), true);
+      expect(File(androidServiceFilePath).existsSync(), true);
+    },
+    timeout: const Timeout(
+      Duration(minutes: 2),
+    ),
+  );
 }