step toward new completion API

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

Index: pkg/analysis_server/lib/src/services/completion/dart/inherited_contributor.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/inherited_contributor.dart b/pkg/analysis_server/lib/src/services/completion/dart/inherited_contributor.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3b56e40881498c36934a5c9bb6dfec90b8f66712
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+++ b/pkg/analysis_server/lib/src/services/completion/dart/inherited_contributor.dart
@@ -0,0 +1,175 @@
+// Copyright (c) 2015, 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.
+
+library services.completion.computer.dart.invocation;
+
+import 'dart:async';
+
+import 'package:analysis_server/src/protocol_server.dart'
+    show CompletionSuggestion, CompletionSuggestionKind, SourceChange;
+import 'package:analysis_server/src/protocol_server.dart' as protocol
+    hide CompletionSuggestion, CompletionSuggestionKind;
+import 'package:analysis_server/src/provisional/completion/completion_core.dart';
+import 'package:analysis_server/src/provisional/completion/completion_dart.dart';
+import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
+import 'package:analysis_server/src/services/completion/dart_completion_manager.dart'
+    show DART_RELEVANCE_HIGH;
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/source.dart';
+// import 'package:analysis_server/plugin/edit/utilities/change_builder_dart.dart';
+// import 'package:analyzer/src/generated/engine.dart';
+
+/**
+ * A completion contributor used to suggest replacing partial identifiers inside
+ * a class declaration with templates for inherited members.
+ */
+class InheritedContributor implements DartCompletionContributor {
+  @override
+  Future<List<CompletionSuggestion>> computeSuggestions(
+      DartCompletionRequest request) async {
+    // Determine if the target looks like a partial identifier
+    // inside a class declaration
+    SimpleIdentifier targetId = _getTargetId(request.target);
+    if (targetId == null) {
+      return EMPTY_LIST;
+    }
+
+    // Partially resolve the compilation unit
+    CompilationUnit unit = await request.resolveDeclarationsInScope();
+    // Gracefully degrade if the compilation unit could not be resolved
+    // e.g. detached part file or source change
+    if (unit == null) {
+      return EMPTY_LIST;
+    }
+
+    // Recompute the target since resolution may have changed it
+    targetId = _getTargetId(request.target);
+    if (targetId == null) {
+      return EMPTY_LIST;
+    }
+    ClassDeclaration classDecl =
+        targetId.getAncestor((p) => p is ClassDeclaration);
+    if (classDecl == null) {
+      return EMPTY_LIST;
+    }
+
+    // Generate a collection of inherited members
+    ClassElement classElem = classDecl.element;
+    InheritanceManager manager = new InheritanceManager(classElem.library);
+    MemberMap map = manager.getMapOfMembersInheritedFromInterfaces(classElem);
+    List<String> memberNames = _computeMemberNames(map, classElem);
+
+    // Build suggestions
+    List<CompletionSuggestion> suggestions = <CompletionSuggestion>[];
+    for (String memberName in memberNames) {
+      ExecutableElement element = map.get(memberName);
+      // Gracefully degrade if the overridden element has not been resolved.
+      if (element.returnType != null) {
+        CompletionSuggestion suggestion =
+            _buildSuggestion(request, targetId, unit, element);
+        if (suggestion != null) {
+          suggestions.add(suggestion);
+        }
+      }
+    }
+    return suggestions;
+  }
+
+  /**
+   * If the target looks like a partial identifier inside a class declaration
+   * then return that identifier, otherwise return `null`.
+   */
+  SimpleIdentifier _getTargetId(CompletionTarget target) {
+    AstNode node = target.containingNode;
+    if (node is ClassDeclaration) {
+      Object entity = target.entity;
+      if (entity is FieldDeclaration) {
+        NodeList<VariableDeclaration> variables = entity.fields.variables;
+        if (variables.length == 1) {
+          SimpleIdentifier targetId = variables[0].name;
+          if (targetId.name.isEmpty) {
+            return targetId;
+          }
+        }
+      }
+    }
+    return null;
+  }
+
+  /**
+   * Return a template for an override of the given [element] in the given
+   * [source]. If selected, the template will replace [targetId].
+   */
+  String _buildRepacementText(Source source, SimpleIdentifier targetId,
+      CompilationUnit unit, ExecutableElement element) {
+    // AnalysisContext context = element.context;
+    // Inject partially resolved unit for use by change builder
+    // DartChangeBuilder builder = new DartChangeBuilder(context, unit);
+    // builder.addFileEdit(source, context.getModificationStamp(source),
+    //     (DartFileEditBuilder builder) {
+    //   builder.addReplacement(targetId.offset, targetId.length,
+    //       (DartEditBuilder builder) {
+    //     builder.writeOverrideOfInheritedMember(element);
+    //   });
+    // });
+    // return builder.sourceChange.edits[0].edits[0].replacement.trim();
+    return '';
+  }
+
+  /**
+   * Build a suggestion to replace [targetId] in the given [unit]
+   * with an override of the given [element].
+   */
+  CompletionSuggestion _buildSuggestion(
+      DartCompletionRequest request,
+      SimpleIdentifier targetId,
+      CompilationUnit unit,
+      ExecutableElement element) {
+    String completion =
+        _buildRepacementText(request.source, targetId, unit, element);
+    if (completion == null || completion.length == 0) {
+      return null;
+    }
+    CompletionSuggestion suggestion = new CompletionSuggestion(
+        CompletionSuggestionKind.IDENTIFIER,
+        DART_RELEVANCE_HIGH,
+        completion,
+        targetId.offset,
+        0,
+        element.isDeprecated,
+        false);
+    suggestion.element = protocol.convertElement(element);
+    return suggestion;
+  }
+
+  /**
+   * Return a list containing the names of all of the inherited but not
+   * implemented members of the class represented by the given [element].
+   * The [map] is used to find all of the members that are inherited.
+   */
+  List<String> _computeMemberNames(MemberMap map, ClassElement element) {
+    List<String> memberNames = <String>[];
+    int count = map.size;
+    for (int i = 0; i < count; i++) {
+      String memberName = map.getKey(i);
+      if (!_hasMember(element, memberName)) {
+        memberNames.add(memberName);
+      }
+    }
+    return memberNames;
+  }
+
+  /**
+   * Return `true` if the given [classElement] directly declares a member with
+   * the given [memberName].
+   */
+  bool _hasMember(ClassElement classElement, String memberName) {
+    return classElement.getField(memberName) != null ||
+        classElement.getGetter(memberName) != null ||
+        classElement.getMethod(memberName) != null ||
+        classElement.getSetter(memberName) != null;
+  }
+}