step toward new completion API

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

+// 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/plugin/edit/utilities/change_builder_dart.dart';
+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_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/engine.dart';
+import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/source.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 null;

[Brian Wilkerson, 2015/11/22 18:02:46]

The documentation for this method doesn't mention allowing `null` as an
equivalent for an empty list, and I think it's better to require an empty list.
(If CompletionSuggestion doesn't have an EMPTY_LIST constant we can add one.)

[danrubel, 2015/11/23 17:47:32]

Done.

+    }
+
+    // Partially resolve the compilation unit

[scheglov, 2015/11/22 05:19:02]

If we pretend that these are sentences, I'd love to have a period at the end :-)

[danrubel, 2015/11/23 17:47:32]

Acknowledged.

+    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 null;
+    }
+
+    // Recompute the target since resolution may have changed it
+    targetId = _getTargetId(request.target);
+    if (targetId == null) {
+      return null;
+    }
+    ClassDeclaration classDecl =
+        targetId.getAncestor((p) => p is ClassDeclaration);
+    if (classDecl == null) {
+      return null;
+    }
+
+    // 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.

[Brian Wilkerson, 2015/11/22 18:02:47]

Is that actually necessary? We already have the context because we have the
resolved compilation unit in which completion is being requested. (In fact, if
the element is from the core library, we could get the wrong context by asking
it.)

[danrubel, 2015/11/23 17:47:32]

I have found situations where the element has not been resolved, I'd like to
keep this guard code.

+      if (element.returnType != null) {
+        CompletionSuggestion suggestion =
+            _buildSuggestion(request, targetId, unit, element);
+        if (suggestion != null) {

[scheglov, 2015/11/22 05:19:02]

It seems that it cannot be null.

[danrubel, 2015/11/23 17:47:32]

It can now. :-)

+          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, Element element) {

[Brian Wilkerson, 2015/11/22 18:02:47]

"Element" --> "ExecutableElement"

[danrubel, 2015/11/23 17:47:32]

Done.

+    AnalysisContext context = element.context;
+    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();
+  }
+
+  /**
+   * 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, Element element) {

[Brian Wilkerson, 2015/11/22 18:02:47]

"Element" --> "ExecutableElement"

[danrubel, 2015/11/23 17:47:32]

Done.

+    String completion =
+        _buildRepacementText(request.source, targetId, unit, element);
+    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;
+  }
+}