add fix for no_duplicate_case_values

See: https://github.com/dart-lang/linter/issues/1374.

Change-Id: Ia09f2530c9a943b8b80fda63fb313b752748264a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/95709
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Phil Quitslund <pquitslund@google.com>

pkg/analysis_server/lib/src/services/correction/fix.dart

@@ -209,6 +209,8 @@ class DartFixKind {
   static const REMOVE_AWAIT = const FixKind('REMOVE_AWAIT', 50, "Remove await");
   static const REMOVE_DEAD_CODE =
       const FixKind('REMOVE_DEAD_CODE', 50, "Remove dead code");
+  static const REMOVE_DUPLICATE_CASE = const FixKind(
+      'REMOVE_DUPLICATE_CASE', 50, "Remove duplicate case statement");
   static const REMOVE_EMPTY_CATCH =
       const FixKind('REMOVE_EMPTY_CATCH', 50, "Remove empty catch clause");
   static const REMOVE_EMPTY_CONSTRUCTOR_BODY = const FixKind(

pkg/analysis_server/lib/src/services/correction/fix_internal.dart

@@ -586,6 +586,9 @@ class FixProcessor {
       if (name == LintNames.empty_statements) {
         await _addFix_removeEmptyStatement();
       }
+      if (name == LintNames.no_duplicate_case_values) {
+        await _addFix_removeCaseStatement();
+      }
       if (name == LintNames.non_constant_identifier_names) {
         await _addFix_renameToCamelCase();
       }
@@ -2699,6 +2702,16 @@ class FixProcessor {
     }
   }
 
+  Future<void> _addFix_removeCaseStatement() async {
+    if (coveredNode is SwitchCase) {
+      var changeBuilder = _newDartChangeBuilder();
+      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
+        builder.addDeletion(utils.getLinesRange(range.node(coveredNode)));
+      });
+      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_DUPLICATE_CASE);
+    }
+  }
+
   Future<void> _addFix_removeConstKeyword() async {
     final instanceCreationExpression = node;
     if (instanceCreationExpression is InstanceCreationExpression) {
@@ -4325,6 +4338,7 @@ class LintNames {
   static const String empty_catches = 'empty_catches';
   static const String empty_constructor_bodies = 'empty_constructor_bodies';
   static const String empty_statements = 'empty_statements';
+  static const String no_duplicate_case_values = 'no_duplicate_case_values';
   static const String non_constant_identifier_names =
       'non_constant_identifier_names';
   static const String prefer_collection_literals = 'prefer_collection_literals';

pkg/analysis_server/test/src/services/correction/fix/remove_duplicate_case_test.dart

@@ -0,0 +1,89 @@
+// Copyright (c) 2018, 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:analysis_server/src/services/correction/fix_internal.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'fix_processor.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(RemoveDuplicateCaseTest);
+  });
+}
+
+@reflectiveTest
+class RemoveDuplicateCaseTest extends FixProcessorLintTest {
+  @override
+  FixKind get kind => DartFixKind.REMOVE_DUPLICATE_CASE;
+
+  @override
+  String get lintCode => LintNames.no_duplicate_case_values;
+
+  test_removeStringCase() async {
+    await resolveTestUnit('''
+void switchString() {
+  String v = 'a';
+  switch (v) {
+    case 'a':
+      print('a');
+      break;
+    case 'b':
+      print('b');
+      break;
+    case 'a' /*LINT*/:
+      print('a');
+      break;
+    default:
+      print('?);
+  }
+}
+''');
+    await assertHasFix('''
+void switchString() {
+  String v = 'a';
+  switch (v) {
+    case 'a':
+      print('a');
+      break;
+    case 'b':
+      print('b');
+      break;
+    default:
+      print('?);
+  }
+}
+''');
+  }
+
+  test_removeIntCase() async {
+    await resolveTestUnit('''
+void switchInt() {
+  switch (2) {
+    case 1:
+      print('a');
+      break;
+    case 2:
+    case 2 /*LINT*/:
+    default:
+      print('?);
+  }
+}
+''');
+    await assertHasFix('''
+void switchInt() {
+  switch (2) {
+    case 1:
+      print('a');
+      break;
+    case 2:
+    default:
+      print('?);
+  }
+}
+''');
+  }
+}