Modify the override_contributor.dart to provide the completions even when no class member characters have been typed.

Change-Id: I03164bcb0761faf7634ec219a1b1cc87dc568fa9
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/144493
Commit-Queue: Jaime Wren <jwren@google.com>
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/services/completion/dart/override_contributor.dart

@@ -15,6 +15,7 @@ import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/nullability_suffix.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/source/source_range.dart';
 import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
 import 'package:analyzer_plugin/src/utilities/completion/completion_target.dart';
 import 'package:analyzer_plugin/utilities/change_builder/change_builder_dart.dart';
@@ -26,14 +27,19 @@ class OverrideContributor implements DartCompletionContributor {
   @override
   Future<List<CompletionSuggestion>> computeSuggestions(
       DartCompletionRequest request, SuggestionBuilder builder) async {
-    var targetId = _getTargetId(request.target);
-    if (targetId == null) {
-      return const <CompletionSuggestion>[];
-    }
-    var classDecl = targetId.thisOrAncestorOfType<ClassOrMixinDeclaration>();
+    var target = request.target;
+    var containingNode = target.containingNode;
+    var classDecl =
+        containingNode.thisOrAncestorOfType<ClassOrMixinDeclaration>();
     if (classDecl == null) {
       return const <CompletionSuggestion>[];
     }
+    if (_inClassMemberBody(containingNode)) {
+      return const <CompletionSuggestion>[];
+    }
+
+    var sourceRange = _getTargetSourceRange(target);
+    sourceRange ??= range.startOffsetEndOffset(request.offset, 0);
 
     var inheritance = InheritanceManager3();
 
@@ -53,7 +59,7 @@ class OverrideContributor implements DartCompletionContributor {
       if (element.returnType != null) {
         var invokeSuper = interface.isSuperImplemented(name);
         var suggestion =
-            await _buildSuggestion(request, targetId, element, invokeSuper);
+            await _buildSuggestion(request, sourceRange, element, invokeSuper);
         if (suggestion != null) {
           suggestions.add(suggestion);
         }
@@ -62,17 +68,17 @@ class OverrideContributor implements DartCompletionContributor {
     return suggestions;
   }
 
-  /// Build a suggestion to replace [targetId] in the given [request] with an
+  /// Build a suggestion to replace [sourceRange] in the given [request] with an
   /// override of the given [element].
   Future<CompletionSuggestion> _buildSuggestion(
       DartCompletionRequest request,
-      SimpleIdentifier targetId,
+      SourceRange sourceRange,
       ExecutableElement element,
       bool invokeSuper) async {
     var displayTextBuffer = StringBuffer();
     var builder = DartChangeBuilder(request.result.session);
     await builder.addFileEdit(request.result.path, (builder) {
-      builder.addReplacement(range.node(targetId), (builder) {
+      builder.addReplacement(sourceRange, (builder) {
         builder.writeOverride(
           element,
           displayTextBuffer: displayTextBuffer,
@@ -102,7 +108,7 @@ class OverrideContributor implements DartCompletionContributor {
     if (selectionRange == null) {
       return null;
     }
-    var offsetDelta = targetId.offset + replacement.indexOf(completion);
+    var offsetDelta = sourceRange.offset + replacement.indexOf(completion);
     var displayText =
         displayTextBuffer.isNotEmpty ? displayTextBuffer.toString() : null;
     var suggestion = CompletionSuggestion(
@@ -118,24 +124,6 @@ class OverrideContributor implements DartCompletionContributor {
     return suggestion;
   }
 
-  /// If the target looks like a partial identifier inside a class declaration
-  /// then return that identifier, otherwise return `null`.
-  SimpleIdentifier _getTargetId(CompletionTarget target) {
-    var node = target.containingNode;
-    if (node is ClassOrMixinDeclaration) {
-      var entity = target.entity;
-      if (entity is FieldDeclaration) {
-        return _getTargetIdFromVarList(entity.fields);
-      }
-    } else if (node is FieldDeclaration) {
-      var entity = target.entity;
-      if (entity is VariableDeclarationList) {
-        return _getTargetIdFromVarList(entity);
-      }
-    }
-    return null;
-  }
-
   SimpleIdentifier _getTargetIdFromVarList(VariableDeclarationList fields) {
     var variables = fields.variables;
     if (variables.length == 1) {
@@ -157,6 +145,29 @@ class OverrideContributor implements DartCompletionContributor {
     return null;
   }
 
+  /// If the target looks like a partial identifier inside a class declaration
+  /// then return that identifier [SourceRange], otherwise return `null`.
+  SourceRange _getTargetSourceRange(CompletionTarget target) {
+    var containingNode = target.containingNode;
+    if (containingNode is ClassOrMixinDeclaration) {
+      if (target.entity is FieldDeclaration) {
+        var fieldDecl = target.entity as FieldDeclaration;
+        var simpleIdentifier = _getTargetIdFromVarList(fieldDecl.fields);
+        if (simpleIdentifier != null) {
+          return range.node(simpleIdentifier);
+        }
+      }
+    } else if (containingNode is FieldDeclaration) {
+      if (target.entity is VariableDeclarationList) {
+        var simpleIdentifier = _getTargetIdFromVarList(target.entity);
+        if (simpleIdentifier != null) {
+          return range.node(simpleIdentifier);
+        }
+      }
+    }
+    return null;
+  }
+
   /// Return `true` if the given [node] has an `override` annotation.
   bool _hasOverride(AstNode node) {
     if (node is AnnotatedNode) {
@@ -205,4 +216,20 @@ class OverrideContributor implements DartCompletionContributor {
       nullabilitySuffix: NullabilitySuffix.none,
     );
   }
+
+  static bool _inClassMemberBody(AstNode node) {
+    /// TODO(jwren) this method was copied from keyword_contributor.dart, all
+    ///  related methods should be moved into a superclass or mixin
+    while (true) {
+      var body = node.thisOrAncestorOfType<FunctionBody>();
+      if (body == null) {
+        return false;
+      }
+      var parent = body.parent;
+      if (parent is ConstructorDeclaration || parent is MethodDeclaration) {
+        return true;
+      }
+      node = parent;
+    }
+  }
 }

pkg/analysis_server/test/services/completion/dart/override_contributor_test.dart

@@ -285,6 +285,24 @@ method() {
         selectionLength: 22);
   }
 
+  Future<void> test_no_target_inClass_of_interface() async {
+    addTestSource('''
+class A {
+  void foo() {}
+}
+
+class B implements A {
+  ^
+}
+''');
+    await computeSuggestions();
+    _assertOverride('''
+@override
+  void foo() {
+    // TODO: implement foo
+  }''', displayText: 'foo() { … }', selectionOffset: 51, selectionLength: 0);
+  }
+
   Future<void> test_outsideOfWorkspace() async {
     testFile = convertPath('/home/other/lib/a.dart');
     addTestSource('''