[linter, DAS] Adds simplify_variable_pattern lint and fix

FMorschel · Commit Queue · commit 3de6f28a1eb8 · 2025-12-11T11:15:11.000-08:00
Fixes: #60518 Change-Id: Id02cc06a68c14bda578058e34050947253a888ee Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/450421 Reviewed-by: Brian Wilkerson <brianwilkerson@google.com> Auto-Submit: Felipe Morschel <git@fmorschel.dev> Reviewed-by: Samuel Rawlins <srawlins@google.com> Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>
diff --git a/pkg/analysis_server/lib/src/services/correction/assist.dart b/pkg/analysis_server/lib/src/services/correction/assist.dart
@@ -402,6 +402,11 @@ abstract final class DartAssistKind {
     DartAssistKindPriority.priority,
     'Remove type annotation',
   );
+  static const removeUnnecessaryName = AssistKind(
+    'dart.assist.remove.unnecessaryName',
+    DartAssistKindPriority.default_,
+    'Remove unnecessary name from pattern',
+  );
   static const replaceConditionalWithIfElse = AssistKind(
     'dart.assist.convert.conditionalToIfElse',
     DartAssistKindPriority.default_,
diff --git a/pkg/analysis_server/lib/src/services/correction/assist_internal.dart b/pkg/analysis_server/lib/src/services/correction/assist_internal.dart
@@ -69,6 +69,7 @@ import 'package:analysis_server/src/services/correction/dart/join_variable_decla
 import 'package:analysis_server/src/services/correction/dart/remove_async.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_digit_separators.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_type_annotation.dart';
+import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_name.dart';
 import 'package:analysis_server/src/services/correction/dart/replace_conditional_with_if_else.dart';
 import 'package:analysis_server/src/services/correction/dart/replace_if_else_with_conditional.dart';
 import 'package:analysis_server/src/services/correction/dart/replace_with_var.dart';
@@ -150,6 +151,7 @@ const Set<ProducerGenerator> _builtInGenerators = {
   JoinIfWithOuter.new,
   JoinVariableDeclaration.new,
   RemoveAsync.new,
+  RemoveUnnecessaryName.new,
   RemoveDigitSeparators.new,
   RemoveTypeAnnotation.other,
   ReplaceConditionalWithIfElse.new,
diff --git a/pkg/analysis_server/lib/src/services/correction/dart/remove_unnecessary_name.dart b/pkg/analysis_server/lib/src/services/correction/dart/remove_unnecessary_name.dart
@@ -0,0 +1,52 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analysis_server/src/services/correction/assist.dart';
+import 'package:analysis_server/src/services/correction/fix.dart';
+import 'package:analysis_server_plugin/edit/dart/correction_producer.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer_plugin/utilities/assist/assist.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:analyzer_plugin/utilities/range_factory.dart';
+
+class RemoveUnnecessaryName extends ResolvedCorrectionProducer {
+  RemoveUnnecessaryName({required super.context});
+
+  @override
+  CorrectionApplicability get applicability =>
+      CorrectionApplicability.automatically;
+
+  @override
+  AssistKind get assistKind => DartAssistKind.removeUnnecessaryName;
+
+  @override
+  FixKind get fixKind => DartFixKind.removeUnnecessaryName;
+
+  @override
+  FixKind? get multiFixKind => DartFixKind.removeUnnecessaryNameMulti;
+
+  @override
+  Future<void> compute(ChangeBuilder builder) async {
+    var node = this.node;
+    if (node.parent case PatternField patternField) {
+      node = patternField;
+    }
+    if (node is! PatternField) {
+      return;
+    }
+
+    var pattern = node.pattern;
+    if (pattern is! DeclaredVariablePattern) return;
+
+    var name = node.name;
+    if (name?.name case Token(:var isSynthetic, :var lexeme) && var name
+        when !isSynthetic && pattern.name.lexeme == lexeme) {
+      await builder.addDartFileEdit(file, (builder) {
+        builder.addDeletion(range.token(name));
+      });
+    }
+  }
+}
diff --git a/pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml b/pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml
@@ -2385,6 +2385,8 @@ require_trailing_commas:
   status: hasFix
 secure_pubspec_urls:
   status: noFix
+simplify_variable_pattern:
+  status: hasFix
 sized_box_for_whitespace:
   status: hasFix
 sized_box_shrink_expand:
diff --git a/pkg/analysis_server/lib/src/services/correction/fix.dart b/pkg/analysis_server/lib/src/services/correction/fix.dart
@@ -1660,6 +1660,16 @@ abstract final class DartFixKind {
     DartFixKindPriority.inFile,
     'Remove all unnecessary casts in file',
   );
+  static const removeUnnecessaryName = FixKind(
+    'dart.fix.remove.unnecessaryName',
+    DartFixKindPriority.standard,
+    'Remove unnecessary name from pattern',
+  );
+  static const removeUnnecessaryNameMulti = FixKind(
+    'dart.fix.remove.unnecessaryName.multi',
+    DartFixKindPriority.inFile,
+    'Remove unnecessary names from patterns in file',
+  );
   static const removeUnnecessaryFinal = FixKind(
     'dart.fix.remove.unnecessaryFinal',
     DartFixKindPriority.standard,
diff --git a/pkg/analysis_server/lib/src/services/correction/fix_internal.dart b/pkg/analysis_server/lib/src/services/correction/fix_internal.dart
@@ -186,6 +186,7 @@ import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_final.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_late.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_library_directive.dart';
+import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_name.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_new.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_parentheses.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_unnecessary_raw_string.dart';
@@ -412,6 +413,7 @@ final _builtInLintGenerators = <DiagnosticCode, List<ProducerGenerator>>{
   ],
   diag.preferVoidToNull: [ReplaceNullWithVoid.new],
   diag.requireTrailingCommas: [AddTrailingComma.new],
+  diag.simplifyVariablePattern: [RemoveUnnecessaryName.new],
   diag.sizedBoxForWhitespace: [ReplaceContainerWithSizedBox.new],
   diag.slashForDocComments: [ConvertDocumentationIntoLine.new],
   diag.sortChildPropertiesLast: [SortChildPropertyLast.new],
diff --git a/pkg/analysis_server/test/src/services/correction/assist/remove_unnecessary_name_test.dart b/pkg/analysis_server/test/src/services/correction/assist/remove_unnecessary_name_test.dart
@@ -0,0 +1,86 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analysis_server/src/services/correction/assist.dart';
+import 'package:analyzer_plugin/utilities/assist/assist.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'assist_processor.dart';
+
+void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(RemoveUnnecessaryNameTest);
+  });
+}
+
+@reflectiveTest
+class RemoveUnnecessaryNameTest extends AssistProcessorTest {
+  @override
+  AssistKind get kind => DartAssistKind.removeUnnecessaryName;
+
+  Future<void> test_objectDestructuring() async {
+    await resolveTestCode('''
+void f(int value) {
+  var int(isEven: is^Even) = value;
+  print(isEven);
+}
+''');
+    await assertHasAssist('''
+void f(int value) {
+  var int(: is^Even) = value;
+  print(isEven);
+}
+''');
+  }
+
+  Future<void> test_objectPatternField_explicit() async {
+    await resolveTestCode('''
+void f(Object o) {
+  if (o case int(isEv^en:var isEven) when isEven) {}
+}
+''');
+    await assertHasAssist('''
+void f(Object o) {
+  if (o case int(:var isEven) when isEven) {}
+}
+''');
+  }
+
+  Future<void> test_objectPatternField_otherName() async {
+    await resolveTestCode('''
+void f(Object o) {
+  if (o case int(isEv^en:var other) when other) {}
+}
+''');
+    await assertNoAssist();
+  }
+
+  Future<void> test_recordDestructuring() async {
+    await resolveTestCode('''
+void f((int, {String name}) record) {
+  var (x, name: na^me) = record;
+  print(name);
+}
+''');
+    await assertHasAssist('''
+void f((int, {String name}) record) {
+  var (x, : name) = record;
+  print(name);
+}
+''');
+  }
+
+  Future<void> test_recordPatternField_explicit() async {
+    await resolveTestCode('''
+void f(({bool isEven,}) o) {
+  if (o case (isEv^en:var isEven) when isEven) {}
+}
+''');
+    await assertHasAssist('''
+void f(({bool isEven,}) o) {
+  if (o case (:var isEven) when isEven) {}
+}
+''');
+  }
+}
diff --git a/pkg/analysis_server/test/src/services/correction/assist/test_all.dart b/pkg/analysis_server/test/src/services/correction/assist/test_all.dart
@@ -94,6 +94,7 @@ import 'join_variable_declaration_test.dart' as join_variable_declaration;
 import 'remove_async_test.dart' as remove_async;
 import 'remove_digit_separators_test.dart' as remove_digit_separators;
 import 'remove_type_annotation_test.dart' as remove_type_annotation;
+import 'remove_unnecessary_name_test.dart' as remove_unnecessary_name;
 import 'replace_conditional_with_if_else_test.dart'
     as replace_conditional_with_if_else;
 import 'replace_if_else_with_conditional_test.dart'
@@ -191,6 +192,7 @@ void main() {
     join_variable_declaration.main();
     remove_async.main();
     remove_digit_separators.main();
+    remove_unnecessary_name.main();
     remove_type_annotation.main();
     replace_conditional_with_if_else.main();
     replace_if_else_with_conditional.main();
diff --git a/pkg/analysis_server/test/src/services/correction/fix/remove_unnecessary_name_test.dart b/pkg/analysis_server/test/src/services/correction/fix/remove_unnecessary_name_test.dart
@@ -0,0 +1,75 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:analysis_server/src/services/correction/fix.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:linter/src/lint_names.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'fix_processor.dart';
+
+void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(RemoveUnnecessaryNameBulkTest);
+    defineReflectiveTests(RemoveUnnecessaryNameTest);
+  });
+}
+
+@reflectiveTest
+class RemoveUnnecessaryNameBulkTest extends BulkFixProcessorTest {
+  @override
+  String get lintCode => LintNames.simplify_variable_pattern;
+
+  Future<void> test_singleFile() async {
+    await parseTestCode('''
+void f(Object o) {
+  if (o case int(isEven:var isEven) when isEven) {}
+  if (o case int(isOdd:var isOdd) when isOdd) {}
+}
+''');
+    await assertHasFix('''
+void f(Object o) {
+  if (o case int(:var isEven) when isEven) {}
+  if (o case int(:var isOdd) when isOdd) {}
+}
+''');
+  }
+}
+
+@reflectiveTest
+class RemoveUnnecessaryNameTest extends FixProcessorLintTest {
+  @override
+  FixKind get kind => DartFixKind.removeUnnecessaryName;
+
+  @override
+  String get lintCode => LintNames.simplify_variable_pattern;
+
+  Future<void> test_patternField_explicit() async {
+    await resolveTestCode('''
+void f(Object o) {
+  if (o case int(isEven:var isEven) when isEven) {}
+}
+''');
+    await assertHasFix('''
+void f(Object o) {
+  if (o case int(:var isEven) when isEven) {}
+}
+''');
+  }
+
+  Future<void> test_recordDestructuring() async {
+    await resolveTestCode('''
+void f((int, {String name}) record) {
+  var (x, name: name) = record;
+  print(name);
+}
+''');
+    await assertHasFix('''
+void f((int, {String name}) record) {
+  var (x, : name) = record;
+  print(name);
+}
+''');
+  }
+}
diff --git a/pkg/analysis_server/test/src/services/correction/fix/test_all.dart b/pkg/analysis_server/test/src/services/correction/fix/test_all.dart
@@ -239,6 +239,7 @@ import 'remove_unnecessary_final_test.dart' as remove_unnecessary_final;
 import 'remove_unnecessary_late_test.dart' as remove_unnecessary_late;
 import 'remove_unnecessary_library_directive_test.dart'
     as remove_unnecessary_library_directive;
+import 'remove_unnecessary_name_test.dart' as remove_unnecessary_name;
 import 'remove_unnecessary_new_test.dart' as remove_unnecessary_new;
 import 'remove_unnecessary_parentheses_test.dart'
     as remove_unnecessary_parentheses;
@@ -528,6 +529,7 @@ void main() {
     remove_unnecessary_final.main();
     remove_unnecessary_late.main();
     remove_unnecessary_library_directive.main();
+    remove_unnecessary_name.main();
     remove_unnecessary_new.main();
     remove_unnecessary_parentheses.main();
     remove_unnecessary_raw_string.main();
diff --git a/pkg/linter/example/all.yaml b/pkg/linter/example/all.yaml
@@ -162,6 +162,7 @@ linter:
     - remove_deprecations_in_breaking_versions
     - require_trailing_commas
     - secure_pubspec_urls
+    - simplify_variable_pattern
     - sized_box_for_whitespace
     - sized_box_shrink_expand
     - slash_for_doc_comments
diff --git a/pkg/linter/lib/src/diagnostic.g.dart b/pkg/linter/lib/src/diagnostic.g.dart
@@ -2737,6 +2737,26 @@ securePubspecUrls = LinterLintTemplate(
   expectedTypes: [ExpectedType.object],
 );
 
+/// Parameters:
+/// String memberName: The redundant member name.
+/// String memberType: The type of the matched object. Whether a field,
+///                    getter, or method.
+const DiagnosticWithArguments<
+  LocatableDiagnostic Function({
+    required String memberName,
+    required String memberType,
+  })
+>
+simplifyVariablePattern = LinterLintTemplate(
+  name: 'simplify_variable_pattern',
+  problemMessage:
+      "The {1} identification '{0}:' is redundant and can be removed.",
+  correctionMessage: "Try removing the redundant {1} identification.",
+  uniqueName: 'simplify_variable_pattern',
+  withArguments: _withArgumentsSimplifyVariablePattern,
+  expectedTypes: [ExpectedType.string, ExpectedType.string],
+);
+
 /// No parameters.
 const LinterLintWithoutArguments sizedBoxForWhitespace =
     LinterLintWithoutArguments(
@@ -4226,6 +4246,16 @@ LocatableDiagnostic _withArgumentsSecurePubspecUrls({required Object p0}) {
   return LocatableDiagnosticImpl(diag.securePubspecUrls, [p0]);
 }
 
+LocatableDiagnostic _withArgumentsSimplifyVariablePattern({
+  required String memberName,
+  required String memberType,
+}) {
+  return LocatableDiagnosticImpl(diag.simplifyVariablePattern, [
+    memberName,
+    memberType,
+  ]);
+}
+
 LocatableDiagnostic _withArgumentsSizedBoxShrinkExpand({required Object p0}) {
   return LocatableDiagnosticImpl(diag.sizedBoxShrinkExpand, [p0]);
 }
diff --git a/pkg/linter/lib/src/lint_names.g.dart b/pkg/linter/lib/src/lint_names.g.dart
@@ -467,6 +467,8 @@ abstract final class LintNames {
 
   static const String secure_pubspec_urls = 'secure_pubspec_urls';
 
+  static const String simplify_variable_pattern = 'simplify_variable_pattern';
+
   static const String sized_box_for_whitespace = 'sized_box_for_whitespace';
 
   static const String sized_box_shrink_expand = 'sized_box_shrink_expand';
diff --git a/pkg/linter/lib/src/rules.dart b/pkg/linter/lib/src/rules.dart
@@ -182,6 +182,7 @@ import 'rules/public_member_api_docs.dart';
 import 'rules/recursive_getters.dart';
 import 'rules/remove_deprecations_in_breaking_version.dart';
 import 'rules/require_trailing_commas.dart';
+import 'rules/simplify_variable_pattern.dart';
 import 'rules/sized_box_for_whitespace.dart';
 import 'rules/sized_box_shrink_expand.dart';
 import 'rules/slash_for_doc_comments.dart';
@@ -436,6 +437,7 @@ void registerLintRules() {
     ..registerLintRule(RemoveDeprecationsInBreakingVersion())
     ..registerLintRule(RequireTrailingCommas())
     ..registerLintRule(SecurePubspecUrls())
+    ..registerLintRule(SimplifyVariablePattern())
     ..registerLintRule(SizedBoxForWhitespace())
     ..registerLintRule(SizedBoxShrinkExpand())
     ..registerLintRule(SlashForDocComments())
diff --git a/pkg/linter/lib/src/rules/simplify_variable_pattern.dart b/pkg/linter/lib/src/rules/simplify_variable_pattern.dart
diff --git a/pkg/linter/messages.yaml b/pkg/linter/messages.yaml
diff --git a/pkg/linter/test/rules/all.dart b/pkg/linter/test/rules/all.dart
diff --git a/pkg/linter/test/rules/simplify_variable_pattern_test.dart b/pkg/linter/test/rules/simplify_variable_pattern_test.dart
