[analysis_server] fix AddNullCheck with null-aware operators

Fixes #50506

Change-Id: I8f7564ec7aaaf32888e9979254e450cd2633e307
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/274442
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

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

@@ -13,10 +13,14 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/extensions.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 AddNullCheck extends CorrectionProducer {
   @override
-  FixKind get fixKind => DartFixKind.ADD_NULL_CHECK;
+  FixKind fixKind = DartFixKind.ADD_NULL_CHECK;
+
+  @override
+  List<Object>? fixArguments;
 
   @override
   Future<void> compute(ChangeBuilder builder) async {
@@ -24,9 +28,15 @@ class AddNullCheck extends CorrectionProducer {
       // Don't suggest a feature that isn't supported.
       return;
     }
+
     Expression? target;
     final coveredNode = this.coveredNode;
     var coveredNodeParent = coveredNode?.parent;
+
+    if (await _isNullAware(builder, coveredNode)) {
+      return;
+    }
+
     if (coveredNode is SimpleIdentifier) {
       if (coveredNodeParent is MethodInvocation) {
         target = coveredNodeParent.realTarget;
@@ -34,6 +44,10 @@ class AddNullCheck extends CorrectionProducer {
         target = coveredNodeParent.prefix;
       } else if (coveredNodeParent is PropertyAccess) {
         target = coveredNodeParent.realTarget;
+      } else if (coveredNodeParent is CascadeExpression &&
+          await _isNullAware(
+              builder, coveredNodeParent.cascadeSections.first)) {
+        return;
       } else {
         target = coveredNode;
       }
@@ -81,6 +95,10 @@ class AddNullCheck extends CorrectionProducer {
       // Adding a null check after an explicit `null` is pointless.
       return;
     }
+
+    if (await _isNullAware(builder, target)) {
+      return;
+    }
     DartType? toType;
     var parent = target.parent;
     if (parent is AssignmentExpression && target == parent.rightHandSide) {
@@ -160,4 +178,42 @@ class AddNullCheck extends CorrectionProducer {
       });
     });
   }
+
+  /// Return `true` if the specified [node] or one of its parents `isNullAware`,
+  /// in which case [_replaceWithNullCheck] would also be called.
+  Future<bool> _isNullAware(ChangeBuilder builder, AstNode? node) async {
+    if (node is PropertyAccess) {
+      if (node.isNullAware) {
+        await _replaceWithNullCheck(builder, node.operator);
+        return true;
+      }
+      return await _isNullAware(builder, node.target);
+    } else if (node is MethodInvocation) {
+      var operator = node.operator;
+      if (operator != null && node.isNullAware) {
+        await _replaceWithNullCheck(builder, operator);
+        return true;
+      }
+      return await _isNullAware(builder, node.target);
+    } else if (node is IndexExpression) {
+      var question = node.question;
+      if (question != null) {
+        await _replaceWithNullCheck(builder, question);
+        return true;
+      }
+      return await _isNullAware(builder, node.target);
+    }
+    return false;
+  }
+
+  /// Replace the null aware [token] with the null check operator.
+  Future<void> _replaceWithNullCheck(ChangeBuilder builder, Token token) async {
+    fixKind = DartFixKind.REPLACE_WITH_NULL_AWARE;
+    var lexeme = token.lexeme;
+    var replacement = '!${lexeme.substring(1)}';
+    fixArguments = [lexeme, replacement];
+    await builder.addDartFileEdit(file, (builder) {
+      builder.addSimpleReplacement(range.token(token), replacement);
+    });
+  }
 }

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

@@ -13,9 +13,124 @@ import 'fix_processor.dart';
 void main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(AddNullCheckTest);
+    defineReflectiveTests(AddNullCheckReplaceWithNullAwareTest);
   });
 }
 
+@reflectiveTest
+class AddNullCheckReplaceWithNullAwareTest extends FixProcessorTest {
+  @override
+  FixKind get kind => DartFixKind.REPLACE_WITH_NULL_AWARE;
+
+  Future<void> test_cascade() async {
+    await resolveTestCode('''
+void g(int i) {}
+void f(int? i) {
+  g(i?..sign);
+}
+''');
+    await assertHasFix('''
+void g(int i) {}
+void f(int? i) {
+  g(i!..sign);
+}
+''');
+  }
+
+  Future<void> test_indexExpression() async {
+    await resolveTestCode('''
+void f(List<int>? l) {
+  l?[0] + 1;
+}
+''');
+    await assertHasFix('''
+void f(List<int>? l) {
+  l![0] + 1;
+}
+''', matchFixMessage: "Replace the '?' with a '!' in the invocation");
+  }
+
+  Future<void> test_indexExpression_notLast() async {
+    await resolveTestCode('''
+void f(List<int>? l) {
+  l?[0].sign + 1;
+}
+''');
+    await assertHasFix('''
+void f(List<int>? l) {
+  l![0].sign + 1;
+}
+''');
+  }
+
+  Future<void> test_methodInvocation() async {
+    await resolveTestCode('''
+void f(String? s) {
+  s?.toString() + '';
+}
+''');
+    await assertHasFix('''
+void f(String? s) {
+  s!.toString() + '';
+}
+''');
+  }
+
+  Future<void> test_methodInvocation_notLast() async {
+    await resolveTestCode('''
+void f(String? s) {
+  s?.toString().toString() + '';
+}
+''');
+    await assertHasFix('''
+void f(String? s) {
+  s!.toString().toString() + '';
+}
+''');
+  }
+
+  Future<void> test_propertyAccess() async {
+    await resolveTestCode('''
+void f(String? s) {
+  s?.length > 1;
+}
+''');
+    await assertHasFix('''
+void f(String? s) {
+  s!.length > 1;
+}
+''');
+  }
+
+  Future<void> test_propertyAccess_coveredNode() async {
+    await resolveTestCode('''
+void g(int i) {}
+void f(int? i) {
+  g(i?.sign);
+}
+''');
+    await assertHasFix('''
+void g(int i) {}
+void f(int? i) {
+  g(i!.sign);
+}
+''');
+  }
+
+  Future<void> test_propertyAccess_notLast() async {
+    await resolveTestCode('''
+void f(String? s) {
+  s?.length.sign > 1;
+}
+''');
+    await assertHasFix('''
+void f(String? s) {
+  s!.length.sign > 1;
+}
+''');
+  }
+}
+
 @reflectiveTest
 class AddNullCheckTest extends FixProcessorTest {
   @override