Add a refactor to convert an unnamed constructor to a named constructor

Let me know whether there are any missed cases that ought to be covered
here. There are tests for the rename constructor that cover a lot of
the additional cases, so I mostly focused here on tests related to where
the refactor is and isn't provided, but that might not be sufficient.

Change-Id: I6e0008597cf852b4acc81a96fa564e0e1a414bd9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/489620
Reviewed-by: Samuel Rawlins <srawlins@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

Author: bwilkerson

pkg/analysis_server/lib/src/services/refactoring/add_constructor_name.dart

@@ -0,0 +1,90 @@
+// Copyright (c) 2026, 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/refactoring/framework/refactoring_producer.dart';
+import 'package:analysis_server/src/services/refactoring/legacy/refactoring.dart';
+import 'package:analysis_server/src/services/search/search_engine_internal.dart';
+import 'package:analysis_server/src/utilities/extensions/selection.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/src/dart/analysis/driver_based_analysis_context.dart';
+import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
+import 'package:language_server_protocol/protocol_custom_generated.dart';
+
+/// The refactoring that adds a name to an unnamed constructor.
+class AddConstructorName extends RefactoringProducer {
+  static const String commandName = 'dart.refactor.add_constructor_name';
+
+  static const String constTitle = 'Add a name to the constructor';
+
+  AddConstructorName(super.context);
+
+  @override
+  bool get isExperimental => false;
+
+  @override
+  List<CommandParameter> get parameters => const <CommandParameter>[];
+
+  @override
+  String get title => constTitle;
+
+  @override
+  Future<ComputeStatus> compute(
+    List<Object?> commandArguments,
+    ChangeBuilder builder,
+  ) async {
+    var element = selection?.constructor(mustNotHaveName: true);
+    if (element == null) {
+      // This should never happen because `isAvailable` would have returned
+      // `false`, so this method wouldn't have been called.
+      return ComputeStatusFailure();
+    }
+
+    var refactoring = _createRefactoring(element);
+    if (refactoring == null) {
+      return ComputeStatusFailure();
+    }
+    refactoring.newName = _computeName(element);
+    var status = await refactoring.checkAllConditions();
+    if (status.hasError) {
+      return ComputeStatusFailure();
+    }
+    await refactoring.createChange(builder: builder);
+    return ComputeStatusSuccess();
+  }
+
+  @override
+  bool isAvailable() {
+    return selection?.constructor(mustNotHaveName: true) != null;
+  }
+
+  /// Compute a name for the new constructor.
+  String _computeName(ConstructorElement element) {
+    var enclosingElement = element.enclosingElement;
+    var usedNames = <String>{};
+    usedNames.addAll(enclosingElement.constructors.map((c) => c.name ?? ''));
+    usedNames.addAll(enclosingElement.methods.map((m) => m.name ?? ''));
+    usedNames.addAll(enclosingElement.fields.map((f) => f.name ?? ''));
+    var candidate = 'name';
+    var index = 1;
+    while (usedNames.contains(candidate)) {
+      candidate = 'name$index';
+      index++;
+    }
+    return candidate;
+  }
+
+  RenameRefactoring? _createRefactoring(ConstructorElement element) {
+    var analysisContext = libraryResult.session.analysisContext;
+    if (analysisContext is! DriverBasedAnalysisContext) {
+      return null;
+    }
+    var driver = analysisContext.driver;
+    var searchEngine = SearchEngineImpl([driver]);
+    return RenameRefactoring.create(
+      RefactoringWorkspace([driver], searchEngine),
+      unitResult,
+      element,
+    );
+  }
+}

pkg/analysis_server/lib/src/services/refactoring/framework/refactoring_processor.dart

@@ -4,6 +4,7 @@
 
 import 'package:analysis_server/src/lsp/constants.dart';
 import 'package:analysis_server/src/services/correction/refactoring_performance.dart';
+import 'package:analysis_server/src/services/refactoring/add_constructor_name.dart';
 import 'package:analysis_server/src/services/refactoring/convert_all_formal_parameters_to_named.dart';
 import 'package:analysis_server/src/services/refactoring/convert_selected_formal_parameters_to_named.dart';
 import 'package:analysis_server/src/services/refactoring/framework/refactoring_context.dart';
@@ -19,6 +20,7 @@ typedef RefactoringProducerGenerator =
 class RefactoringProcessor {
   /// A list of the generators used to produce refactorings.
   static const Map<String, RefactoringProducerGenerator> generators = {
+    AddConstructorName.commandName: AddConstructorName.new,
     ConvertAllFormalParametersToNamed.commandName:
         ConvertAllFormalParametersToNamed.new,
     ConvertSelectedFormalParametersToNamed.commandName:

pkg/analysis_server/lib/src/services/refactoring/legacy/rename_constructor.dart

@@ -61,7 +61,6 @@ class RenameConstructorRefactoringImpl extends RenameRefactoringImpl {
         });
         continue;
       } else if (coveringParent is ConstructorDeclaration &&
-          // TODO(scheglov): support primary constructors
           coveringParent.typeName!.offset == reference.range.offset) {
         await builder.addDartFileEdit(reference.file, (builder) {
           _addSuperInvocationToConstructor(

pkg/analysis_server/lib/src/utilities/extensions/selection.dart

@@ -0,0 +1,76 @@
+// Copyright (c) 2026, 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_plugin/src/utilities/selection.dart';
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+
+extension SelectionExtension on Selection {
+  /// The end of the selection.
+  int get end => offset + length;
+
+  /// Returns the element of the constructor at the given [selection].
+  ///
+  /// Returns `null` if
+  /// - the selection doesn't identify a constructor, or
+  /// - [mustHaveName] is `true` and the referenced constructor doesn't have a
+  ///   name, or
+  /// - [mustNotHaveName] is `true` and the referenced constructor has a name.
+  ConstructorElement? constructor({
+    bool mustHaveName = false,
+    bool mustNotHaveName = false,
+  }) {
+    var node = coveringNode;
+
+    bool meetsRequirements(Object? name) {
+      if (name == null) {
+        if (mustHaveName) return false;
+      } else {
+        if (mustNotHaveName) return false;
+      }
+      return true;
+    }
+
+    if (node is ConstructorDeclaration) {
+      if (!meetsRequirements(node.name)) return null;
+      var left =
+          node.typeName?.offset ??
+          node.factoryKeyword?.offset ??
+          node.newKeyword?.offset ??
+          node.firstTokenAfterCommentAndMetadata.offset;
+      var right = node.separator?.offset ?? node.parameters.offset;
+      if (left <= offset && end <= right) {
+        return node.declaredFragment?.element;
+      }
+    } else if (node is SimpleIdentifier || node is FormalParameterList) {
+      var parent = node.parent;
+      if (parent is ConstructorDeclaration) {
+        if (!meetsRequirements(parent.name)) return null;
+        return parent.declaredFragment?.element;
+      } else if (parent is ConstructorName) {
+        if (!meetsRequirements(parent.name)) return null;
+        return parent.element;
+      }
+    } else if (node is PrimaryConstructorDeclaration) {
+      if (!meetsRequirements(node.constructorName)) return null;
+      return node.declaredFragment?.element;
+    } else if (node is PrimaryConstructorName) {
+      if (!meetsRequirements(node.name)) return null;
+      var parent = node.parent;
+      if (parent is PrimaryConstructorDeclaration) {
+        return parent.declaredFragment?.element;
+      }
+    } else if (node is NamedType) {
+      var parent = node.parent;
+      if (parent is ConstructorName) {
+        if (!meetsRequirements(node.name)) return null;
+        return parent.element;
+      }
+    } else if (node is ConstructorName) {
+      if (!meetsRequirements(node.name)) return null;
+      return node.element;
+    }
+    return null;
+  }
+}