Add .env file support for option `--dart-define-from-file` (#128668)

# Proposal

I suggest to make possible to specify .env files to the --dart-define-from-file in addition to the Json format.

# Issue

Close #128667

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -612,17 +612,17 @@ abstract class FlutterCommand extends Command<void> {
       valueHelp: 'foo=bar',
       splitCommas: false,
     );
-    useDartDefineConfigJsonFileOption();
+    useDartDefineFromFileOption();
   }
 
-  void useDartDefineConfigJsonFileOption() {
+  void useDartDefineFromFileOption() {
     argParser.addMultiOption(
       FlutterOptions.kDartDefineFromFileOption,
-      help: 'The path of a json format file where flutter define a global constant pool. '
-          'Json entry will be available as constants from the String.fromEnvironment, bool.fromEnvironment, '
-          'and int.fromEnvironment constructors; the key and field are json values.\n'
+      help:
+          'The path of a .json or .env file containing key-value pairs that will be available as environment variables.\n'
+          'These can be accessed using the String.fromEnvironment, bool.fromEnvironment, and int.fromEnvironment constructors.\n'
           'Multiple defines can be passed by repeating "--${FlutterOptions.kDartDefineFromFileOption}" multiple times.',
-      valueHelp: 'use-define-config.json',
+      valueHelp: 'use-define-config.json|.env',
       splitCommas: false,
     );
   }
@@ -1341,18 +1341,29 @@ abstract class FlutterCommand extends Command<void> {
     final Map<String, Object?> dartDefineConfigJsonMap = <String, Object?>{};
 
     if (argParser.options.containsKey(FlutterOptions.kDartDefineFromFileOption)) {
-      final List<String> configJsonPaths = stringsArg(
+      final List<String> configFilePaths = stringsArg(
         FlutterOptions.kDartDefineFromFileOption,
       );
 
-      for (final String path in configJsonPaths) {
+      for (final String path in configFilePaths) {
         if (!globals.fs.isFileSync(path)) {
           throwToolExit('Json config define file "--${FlutterOptions
               .kDartDefineFromFileOption}=$path" is not a file, '
               'please fix first!');
         }
 
-        final String configJsonRaw = globals.fs.file(path).readAsStringSync();
+        final String configRaw = globals.fs.file(path).readAsStringSync();
+
+        // Determine whether the file content is JSON or .env format.
+        String configJsonRaw;
+        if (configRaw.trim().startsWith('{')) {
+          configJsonRaw = configRaw;
+        } else {
+
+          // Convert env file to JSON.
+          configJsonRaw = convertEnvFileToJsonRaw(configRaw);
+        }
+
         try {
           // Fix json convert Object value :type '_InternalLinkedHashMap<String, dynamic>' is not a subtype of type 'Map<String, Object>' in type cast
           (json.decode(configJsonRaw) as Map<String, dynamic>)
@@ -1370,6 +1381,88 @@ abstract class FlutterCommand extends Command<void> {
     return dartDefineConfigJsonMap;
   }
 
+  /// Parse a property line from an env file.
+  /// Supposed property structure should be:
+  ///   key=value
+  ///
+  /// Where: key is a string without spaces and value is a string.
+  /// Value can also contain '=' char.
+  ///
+  /// Returns a record of key and value as strings.
+  MapEntry<String, String> _parseProperty(String line) {
+    final RegExp blockRegExp = RegExp(r'^\s*([a-zA-Z_]+[a-zA-Z0-9_]*)\s*=\s*"""\s*(.*)$');
+    if (blockRegExp.hasMatch(line)) {
+      throwToolExit('Multi-line value is not supported: $line');
+    }
+
+    final RegExp propertyRegExp = RegExp(r'^\s*([a-zA-Z_]+[a-zA-Z0-9_]*)\s*=\s*(.*)?$');
+    final Match? match = propertyRegExp.firstMatch(line);
+    if (match == null) {
+      throwToolExit('Unable to parse file provided for '
+        '--${FlutterOptions.kDartDefineFromFileOption}.\n'
+        'Invalid property line: $line');
+    }
+
+    final String key = match.group(1)!;
+    final String value = match.group(2) ?? '';
+
+    // Remove wrapping quotes and trailing line comment.
+    final RegExp doubleQuoteValueRegExp = RegExp(r'^"(.*)"\s*(\#\s*.*)?$');
+    final Match? doubleQuoteValue = doubleQuoteValueRegExp.firstMatch(value);
+    if (doubleQuoteValue != null) {
+      return MapEntry<String, String>(key, doubleQuoteValue.group(1)!);
+    }
+
+    final RegExp quoteValueRegExp = RegExp(r"^'(.*)'\s*(\#\s*.*)?$");
+    final Match? quoteValue = quoteValueRegExp.firstMatch(value);
+    if (quoteValue != null) {
+      return MapEntry<String, String>(key, quoteValue.group(1)!);
+    }
+
+    final RegExp backQuoteValueRegExp = RegExp(r'^`(.*)`\s*(\#\s*.*)?$');
+    final Match? backQuoteValue = backQuoteValueRegExp.firstMatch(value);
+    if (backQuoteValue != null) {
+      return MapEntry<String, String>(key, backQuoteValue.group(1)!);
+    }
+
+    final RegExp noQuoteValueRegExp = RegExp(r'^([^#\n\s]*)\s*(?:\s*#\s*(.*))?$');
+    final Match? noQuoteValue = noQuoteValueRegExp.firstMatch(value);
+    if (noQuoteValue != null) {
+      return MapEntry<String, String>(key, noQuoteValue.group(1)!);
+    }
+
+    return MapEntry<String, String>(key, value);
+  }
+
+  /// Converts an .env file string to its equivalent JSON string.
+  ///
+  /// For example, the .env file string
+  ///   key=value # comment
+  ///   complexKey="foo#bar=baz"
+  /// would be converted to a JSON string equivalent to:
+  ///   {
+  ///     "key": "value",
+  ///     "complexKey": "foo#bar=baz"
+  ///   }
+  ///
+  /// Multiline values are not supported.
+  String convertEnvFileToJsonRaw(String configRaw) {
+    final List<String> lines = configRaw
+        .split('\n')
+        .map((String line) => line.trim())
+        .where((String line) => line.isNotEmpty)
+        .where((String line) => !line.startsWith('#')) // Remove comment lines.
+        .toList();
+
+    final Map<String, String> propertyMap = <String, String>{};
+    for (final String line in lines) {
+      final MapEntry<String, String> property = _parseProperty(line);
+      propertyMap[property.key] = property.value;
+    }
+
+    return jsonEncode(propertyMap);
+  }
+
   /// Updates dart-defines based on [webRenderer].
   @visibleForTesting
   static List<String> updateDartDefines(List<String> dartDefines, WebRendererMode webRenderer) {

packages/flutter_tools/test/commands.shard/permeable/build_bundle_test.dart

@@ -518,7 +518,8 @@ void main() {
           "kDouble": 1.1,
           "name": "denghaizhu",
           "title": "this is title from config json file",
-          "nullValue": null
+          "nullValue": null,
+          "containEqual": "sfadsfv=432f"
         }
       '''
     );
@@ -549,6 +550,7 @@ void main() {
           'name=denghaizhu',
           'title=this is title from config json file',
           'nullValue=null',
+          'containEqual=sfadsfv=432f',
           'body=this is body from config json file',
         ]),
       );
@@ -557,6 +559,155 @@ void main() {
     ProcessManager: () => FakeProcessManager.any(),
   });
 
+  testUsingContext('--dart-define-from-file correctly parses a valid env file', () async {
+    globals.fs
+        .file(globals.fs.path.join('lib', 'main.dart'))
+        .createSync(recursive: true);
+    globals.fs.file('pubspec.yaml').createSync();
+    globals.fs.file('.packages').createSync();
+    await globals.fs.file('.env').writeAsString('''
+        # comment
+        kInt=1
+        kDouble=1.1 # should be double
+
+        name=piotrfleury
+        title=this is title from config env file
+        empty=
+
+        doubleQuotes="double quotes 'value'#=" # double quotes
+        singleQuotes='single quotes "value"#=' # single quotes
+        backQuotes=`back quotes "value" '#=` # back quotes
+
+        hashString="some-#-hash-string-value"
+
+        # Play around with spaces around the equals sign.
+        spaceBeforeEqual =value
+        spaceAroundEqual = value
+        spaceAfterEqual= value
+
+      ''');
+    await globals.fs.file('.env2').writeAsString('''
+        # second comment
+
+        body=this is body from config env file
+      ''');
+    final CommandRunner<void> runner =
+        createTestCommandRunner(BuildBundleCommand(
+      logger: BufferLogger.test(),
+    ));
+
+    await runner.run(<String>[
+      'bundle',
+      '--no-pub',
+      '--dart-define-from-file=.env',
+      '--dart-define-from-file=.env2',
+    ]);
+  }, overrides: <Type, Generator>{
+    BuildSystem: () => TestBuildSystem.all(BuildResult(success: true),
+            (Target target, Environment environment) {
+          expect(
+            _decodeDartDefines(environment),
+            containsAllInOrder(const <String>[
+              'kInt=1',
+              'kDouble=1.1',
+              'name=piotrfleury',
+              'title=this is title from config env file',
+              'empty=',
+              "doubleQuotes=double quotes 'value'#=",
+              'singleQuotes=single quotes "value"#=',
+              'backQuotes=back quotes "value" \'#=',
+              'hashString=some-#-hash-string-value',
+              'spaceBeforeEqual=value',
+              'spaceAroundEqual=value',
+              'spaceAfterEqual=value',
+              'body=this is body from config env file'
+            ]),
+          );
+        }),
+    FileSystem: fsFactory,
+    ProcessManager: () => FakeProcessManager.any(),
+  });
+
+  testUsingContext('--dart-define-from-file option env file throws a ToolExit when .env file contains a multiline value', () async {
+    globals.fs
+        .file(globals.fs.path.join('lib', 'main.dart'))
+        .createSync(recursive: true);
+    globals.fs.file('pubspec.yaml').createSync();
+    globals.fs.file('.packages').createSync();
+    await globals.fs.file('.env').writeAsString('''
+        # single line value
+        name=piotrfleury
+
+        # multi-line value
+        multiline = """ Welcome to .env demo
+        a simple counter app with .env file support
+        for more info, check out the README.md file
+        Thanks! """ # This is the welcome message that will be displayed on the counter app
+
+      ''');
+    final CommandRunner<void> runner =
+        createTestCommandRunner(BuildBundleCommand(
+      logger: BufferLogger.test(),
+    ));
+
+    expect(() => runner.run(<String>[
+      'bundle',
+      '--no-pub',
+      '--dart-define-from-file=.env',
+    ]), throwsToolExit(message: 'Multi-line value is not supported: multiline = """ Welcome to .env demo'));
+  }, overrides: <Type, Generator>{
+    BuildSystem: () => TestBuildSystem.all(BuildResult(success: true)),
+    FileSystem: fsFactory,
+    ProcessManager: () => FakeProcessManager.any(),
+  });
+
+  testUsingContext('--dart-define-from-file option works with mixed file formats',
+      () async {
+    globals.fs
+        .file(globals.fs.path.join('lib', 'main.dart'))
+        .createSync(recursive: true);
+    globals.fs.file('pubspec.yaml').createSync();
+    globals.fs.file('.packages').createSync();
+    await globals.fs.file('.env').writeAsString('''
+        kInt=1
+        kDouble=1.1
+        name=piotrfleury
+        title=this is title from config env file
+      ''');
+    await globals.fs.file('config.json').writeAsString('''
+        {
+          "body": "this is body from config json file"
+        }
+      ''');
+    final CommandRunner<void> runner =
+        createTestCommandRunner(BuildBundleCommand(
+      logger: BufferLogger.test(),
+    ));
+
+    await runner.run(<String>[
+      'bundle',
+      '--no-pub',
+      '--dart-define-from-file=.env',
+      '--dart-define-from-file=config.json',
+    ]);
+  }, overrides: <Type, Generator>{
+    BuildSystem: () => TestBuildSystem.all(BuildResult(success: true),
+            (Target target, Environment environment) {
+          expect(
+            _decodeDartDefines(environment),
+            containsAllInOrder(const <String>[
+              'kInt=1',
+              'kDouble=1.1',
+              'name=piotrfleury',
+              'title=this is title from config env file',
+              'body=this is body from config json file',
+            ]),
+          );
+        }),
+    FileSystem: fsFactory,
+    ProcessManager: () => FakeProcessManager.any(),
+  });
+
   testUsingContext('test --dart-define-from-file option if conflict', () async {
     globals.fs.file(globals.fs.path.join('lib', 'main.dart')).createSync(recursive: true);
     globals.fs.file('pubspec.yaml').createSync();