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fix: handle non-FlutterFire-generated firebase_options.dart gracefully #430

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fix: handle non-FlutterFire-generated firebase_options.dart gracefully #430

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ba0cf72
fix: handle non-FlutterFire-generated firebase_options.dart gracefully
solvejet-team Mar 29, 2026
b32853c
refactor: use CLI header comment for file detection per review feedback
solvejet-team Mar 29, 2026
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138 changes: 62 additions & 76 deletions packages/flutterfire_cli/lib/src/firebase/firebase_dart_configuration_write.dart
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Original file line number Diff line number Diff line change
Expand Up @@ -53,12 +53,12 @@ class FirebaseDartConfigurationWrite {

FirebaseJsonWrites write() {
final outputFile = File(configurationFilePath);
if (outputFile.existsSync()) {
final updatedFileString = _updateExistingConfigurationFile(
outputFile,
);
if (outputFile.existsSync() && _isFlutterFireGeneratedFile(outputFile)) {
final updatedFileString = _updateExistingConfigurationFile(outputFile);
outputFile.writeAsStringSync(updatedFileString);
} else {
// File doesn't exist or wasn't generated by FlutterFire CLI
// (e.g. a placeholder file). Generate from scratch.
_writeHeader();
_writeClass();

Expand All @@ -69,9 +69,15 @@ class FirebaseDartConfigurationWrite {
return _firebaseJsonWrites();
}

String _updateExistingConfigurationFile(
File outputFile,
) {
/// Checks whether the existing file was generated by FlutterFire CLI
/// by looking for the CLI's header comment.
/// Returns false for placeholder or manually written files.
bool _isFlutterFireGeneratedFile(File file) {
final contents = file.readAsStringSync();
return contents.startsWith('// File generated by FlutterFire CLI.');
}
Comment on lines +72 to +78
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@gemini-code-assist gemini-code-assist bot Mar 29, 2026

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medium

The current check for whether a file is generated by FlutterFire CLI is based on the presence of certain keywords. This might be brittle and could lead to false positives if a user's placeholder file happens to contain these keywords.

A more robust method would be to check for the specific comment header // File generated by FlutterFire CLI. that this tool adds to the beginning of every generated file. This is a much stronger and more reliable signal that the file was auto-generated.

  /// Checks whether the existing file was generated by FlutterFire CLI
  /// by looking for the header comment.
  /// Returns false for placeholder or manually written files.
  bool _isFlutterFireGeneratedFile(File file) {
    final contents = file.readAsStringSync();
    return contents.startsWith('// File generated by FlutterFire CLI.');
  }


String _updateExistingConfigurationFile(File outputFile) {
final fileConfigurationLines = outputFile.readAsLinesSync();

final optionsList = [
Expand All @@ -92,8 +98,9 @@ class FirebaseDartConfigurationWrite {
if (options == null) continue;

final configExists = fileConfigurationLines.any(
(line) => line
.contains('static const FirebaseOptions ${platform.toLowerCase()}'),
(line) => line.contains(
'static const FirebaseOptions ${platform.toLowerCase()}',
),
);
if (configExists) {
// find the indexes for start/end of existing platform configuration
Expand All @@ -118,10 +125,7 @@ class FirebaseDartConfigurationWrite {
// Insert the new platform configuration
fileConfigurationLines.insertAll(
startIndex - 1,
_buildFirebaseOptions(
options,
platform.toLowerCase(),
),
_buildFirebaseOptions(options, platform.toLowerCase()),
);
} else {
// remove `UnsupportedError` and write static const FirebaseOptions $platform
Expand All @@ -132,8 +136,9 @@ class FirebaseDartConfigurationWrite {
);
final unsupportedErrorLineIndex = startIndex + 1;

if (fileConfigurationLines[unsupportedErrorLineIndex]
.contains('UnsupportedError')) {
if (fileConfigurationLines[unsupportedErrorLineIndex].contains(
'UnsupportedError',
)) {
final endIndex = fileConfigurationLines.indexWhere(
(line) => line.contains(');'),
unsupportedErrorLineIndex,
Expand All @@ -150,18 +155,19 @@ class FirebaseDartConfigurationWrite {
: ' return ${platform.toLowerCase()};',
);
} else {
throw Exception('`UnsupportedError` not found in $platform');
throw Exception(
'Unable to update existing firebase_options.dart for platform '
'$platform. The file exists but does not match the expected '
'format. Delete the file and re-run `flutterfire configure`.',
);
}

final insertIndex = fileConfigurationLines.lastIndexOf('}');

// write the static property for the platform
fileConfigurationLines.insertAll(
insertIndex,
_buildFirebaseOptions(
options,
platform.toLowerCase(),
),
_buildFirebaseOptions(options, platform.toLowerCase()),
);
}
}
Expand All @@ -179,10 +185,7 @@ class FirebaseDartConfigurationWrite {
});
}

List<String> _buildFirebaseOptions(
FirebaseOptions options,
String platform,
) {
List<String> _buildFirebaseOptions(FirebaseOptions options, String platform) {
return <String>[
'',
' static const FirebaseOptions $platform = FirebaseOptions(',
Expand All @@ -196,10 +199,7 @@ class FirebaseDartConfigurationWrite {

FirebaseJsonWrites _firebaseJsonWrites() {
final relativePathConfigurationFile = replaceBackslash(
relative(
configurationFilePath,
from: flutterAppPath,
),
relative(configurationFilePath, from: flutterAppPath),
);

final keysToMap = [
Expand Down Expand Up @@ -238,56 +238,48 @@ class FirebaseDartConfigurationWrite {
}

void _writeHeader() {
_stringBuffer.writeAll(
<String>[
'// File generated by FlutterFire CLI.',
'// ignore_for_file: type=lint',
"import 'package:firebase_core/firebase_core.dart' show FirebaseOptions;",
"import 'package:flutter/foundation.dart'",
' show defaultTargetPlatform, kIsWeb, TargetPlatform;',
'',
'/// Default [FirebaseOptions] for use with your Firebase apps.',
'///',
'/// Example:',
'/// ```dart',
"/// import '${basename(configurationFilePath)}';",
'/// // ...',
'/// await Firebase.initializeApp(',
'/// options: DefaultFirebaseOptions.currentPlatform,',
'/// );',
'/// ```',
'',
],
'\n',
);
_stringBuffer.writeAll(<String>[
'// File generated by FlutterFire CLI.',
'// ignore_for_file: type=lint',
"import 'package:firebase_core/firebase_core.dart' show FirebaseOptions;",
"import 'package:flutter/foundation.dart'",
' show defaultTargetPlatform, kIsWeb, TargetPlatform;',
'',
'/// Default [FirebaseOptions] for use with your Firebase apps.',
'///',
'/// Example:',
'/// ```dart',
"/// import '${basename(configurationFilePath)}';",
'/// // ...',
'/// await Firebase.initializeApp(',
'/// options: DefaultFirebaseOptions.currentPlatform,',
'/// );',
'/// ```',
'',
], '\n');
}

void _writeClass() {
_stringBuffer.writeAll(
<String>[
'class DefaultFirebaseOptions {',
' static FirebaseOptions get currentPlatform {',
'',
],
'\n',
);
_stringBuffer.writeAll(<String>[
'class DefaultFirebaseOptions {',
' static FirebaseOptions get currentPlatform {',
'',
], '\n');
_writeCurrentPlatformWeb();
_stringBuffer.writeln(' switch (defaultTargetPlatform) {');
_writeCurrentPlatformSwitchAndroid();
_writeCurrentPlatformSwitchIos();
_writeCurrentPlatformSwitchMacos();
_writeCurrentPlatformSwitchWindows();
_writeCurrentPlatformSwitchLinux();
_stringBuffer.write(
'''
_stringBuffer.write('''
default:
throw UnsupportedError(
'DefaultFirebaseOptions are not supported for this platform.',
);
}
}
''',
);
''');
_writeFirebaseOptionsStatic(kWeb, webOptions);
_writeFirebaseOptionsStatic(kAndroid, androidOptions);
_writeFirebaseOptionsStatic(kIos, iosOptions);
Expand All @@ -299,23 +291,17 @@ class FirebaseDartConfigurationWrite {

void _writeFirebaseOptionsStatic(String platform, FirebaseOptions? options) {
if (options == null) return;
_stringBuffer.writeAll(
_buildFirebaseOptions(options, platform),
'\n',
);
_stringBuffer.writeAll(_buildFirebaseOptions(options, platform), '\n');
}

void _writeThrowUnsupportedForPlatform(String platform, String indentation) {
_stringBuffer.writeAll(
<String>[
'${indentation}throw UnsupportedError(',
"$indentation 'DefaultFirebaseOptions have not been configured for $platform - '",
"$indentation 'you can reconfigure this by running the FlutterFire CLI again.',",
'$indentation);',
'',
],
'\n',
);
_stringBuffer.writeAll(<String>[
'${indentation}throw UnsupportedError(',
"$indentation 'DefaultFirebaseOptions have not been configured for $platform - '",
"$indentation 'you can reconfigure this by running the FlutterFire CLI again.',",
'$indentation);',
'',
], '\n');
}

void _writeCurrentPlatformWeb() {
Expand Down
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