fix for unnecessary_null_aware_assignments

Fixes: https://github.com/dart-lang/lints/issues/66

Change-Id: Ib14902c76910d550fbf69161a257d59cd268be9c
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/236701
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Phil Quitslund <[email protected]>

Author: pq

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

@@ -0,0 +1,52 @@
+// Copyright (c) 2022, 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/dart/abstract_producer.dart';
+import 'package:analysis_server/src/services/correction/fix.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/source/source_range.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 RemoveAssignment extends CorrectionProducer {
+  @override
+  bool get canBeAppliedInBulk => true;
+
+  @override
+  bool get canBeAppliedToFile => true;
+
+  @override
+  FixKind get fixKind => DartFixKind.REMOVE_ASSIGNMENT;
+
+  @override
+  FixKind get multiFixKind => DartFixKind.REMOVE_ASSIGNMENT_MULTI;
+
+  @override
+  Future<void> compute(ChangeBuilder builder) async {
+    var expression = node;
+    if (expression is! AssignmentExpression) {
+      return;
+    }
+
+    SourceRange sourceRange;
+    var parent = expression.parent;
+    while (parent is ParenthesizedExpression) {
+      parent = parent.parent;
+    }
+    if (parent is ExpressionStatement) {
+      sourceRange = utils.getLinesRange(range.node(parent));
+    } else {
+      sourceRange = range.endEnd(
+          expression.leftHandSide.endToken, expression.rightHandSide.endToken);
+    }
+
+    await builder.addDartFileEdit(file, (builder) {
+      builder.addDeletion(sourceRange);
+    });
+  }
+
+  /// Return an instance of this class. Used as a tear-off in `FixProcessor`.
+  static RemoveAssignment newInstance() => RemoveAssignment();
+}

pkg/analysis_server/lib/src/services/correction/error_fix_status.yaml

@@ -1783,7 +1783,7 @@ LintCode.unnecessary_late:
 LintCode.unnecessary_new:
   status: hasFix
 LintCode.unnecessary_null_aware_assignments:
-  status: needsFix
+  status: hasFix
 LintCode.unnecessary_null_checks:
   status: needsEvaluation
 LintCode.unnecessary_null_in_if_null_operators:

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

@@ -829,6 +829,16 @@ class DartFixKind {
     DartFixKindPriority.IN_FILE,
     'Remove arguments in file',
   );
+  static const REMOVE_ASSIGNMENT = FixKind(
+    'dart.fix.remove.assignment',
+    DartFixKindPriority.DEFAULT,
+    'Remove assignment',
+  );
+  static const REMOVE_ASSIGNMENT_MULTI = FixKind(
+    'dart.fix.remove.assignment.multi',
+    DartFixKindPriority.IN_FILE,
+    'Remove unnecessary assignments everywhere in file',
+  );
   static const REMOVE_AWAIT = FixKind(
     'dart.fix.remove.await',
     DartFixKindPriority.DEFAULT,

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

@@ -104,6 +104,7 @@ import 'package:analysis_server/src/services/correction/dart/qualify_reference.d
 import 'package:analysis_server/src/services/correction/dart/remove_abstract.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_annotation.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_argument.dart';
+import 'package:analysis_server/src/services/correction/dart/remove_assignment.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_await.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_comparison.dart';
 import 'package:analysis_server/src/services/correction/dart/remove_const.dart';
@@ -628,6 +629,9 @@ class FixProcessor extends BaseProcessor {
     LintNames.unnecessary_new: [
       RemoveUnnecessaryNew.newInstance,
     ],
+    LintNames.unnecessary_null_aware_assignments: [
+      RemoveAssignment.newInstance,
+    ],
     LintNames.unnecessary_null_in_if_null_operators: [
       RemoveIfNullOperator.newInstance,
     ],

pkg/analysis_server/lib/src/services/linter/lint_names.dart

@@ -136,6 +136,8 @@ class LintNames {
   static const String unnecessary_lambdas = 'unnecessary_lambdas';
   static const String unnecessary_late = 'unnecessary_late';
   static const String unnecessary_new = 'unnecessary_new';
+  static const String unnecessary_null_aware_assignments =
+      'unnecessary_null_aware_assignments';
   static const String unnecessary_null_in_if_null_operators =
       'unnecessary_null_in_if_null_operators';
   static const String unnecessary_nullable_for_final_variable_declarations =

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

@@ -0,0 +1,88 @@
+// Copyright (c) 2022, 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/linter/lint_names.dart';
+import 'package:analyzer_plugin/utilities/fixes/fixes.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+import 'fix_processor.dart';
+
+void main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(RemoveAssignmentBulkTest);
+    defineReflectiveTests(RemoveAssignmentTest);
+  });
+}
+
+@reflectiveTest
+class RemoveAssignmentBulkTest extends BulkFixProcessorTest {
+  @override
+  String get lintCode => LintNames.unnecessary_null_aware_assignments;
+
+  Future<void> test_singleFile() async {
+    await resolveTestCode('''
+void f() {
+  var x;
+  var y;
+  x ??= null;
+  y ??= null;
+}
+''');
+    await assertHasFix('''
+void f() {
+  var x;
+  var y;
+}
+''');
+  }
+}
+
+@reflectiveTest
+class RemoveAssignmentTest extends FixProcessorLintTest {
+  @override
+  FixKind get kind => DartFixKind.REMOVE_ASSIGNMENT;
+
+  @override
+  String get lintCode => LintNames.unnecessary_null_aware_assignments;
+
+  Future<void> test_assignment() async {
+    await resolveTestCode('''
+void f() {
+  var x;
+  x ??= null;
+}
+''');
+    await assertHasFix('''
+void f() {
+  var x;
+}
+''');
+  }
+
+  Future<void> test_assignment_compound() async {
+    await resolveTestCode('''
+void f(x, y) {
+  y = x ??= null;
+}
+''');
+    await assertHasFix('''
+void f(x, y) {
+  y = x;
+}
+''');
+  }
+
+  Future<void> test_assignment_parenthesized() async {
+    await resolveTestCode('''
+void f(int? x) {
+  (x ??= null);
+}
+''');
+    await assertHasFix('''
+void f(int? x) {
+}
+''');
+  }
+}

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

@@ -129,6 +129,7 @@ import 'qualify_reference_test.dart' as qualify_reference;
 import 'remove_abstract_test.dart' as remove_abstract;
 import 'remove_annotation_test.dart' as remove_annotation;
 import 'remove_argument_test.dart' as remove_argument;
+import 'remove_assignment_test.dart' as remove_assignment;
 import 'remove_await_test.dart' as remove_await;
 import 'remove_comparison_test.dart' as remove_comparison;
 import 'remove_const_test.dart' as remove_const;
@@ -337,6 +338,7 @@ void main() {
     remove_abstract.main();
     remove_annotation.main();
     remove_argument.main();
+    remove_assignment.main();
     remove_await.main();
     remove_comparison.main();
     remove_const.main();