hook new DartCompletionContributor API into existing framework

pkg/analysis_server/lib/src/services/completion/completion_dart.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 analysis_server.src.services.completion.completion_dart;
-
-import 'dart:async';
-
-import 'package:analysis_server/src/provisional/completion/completion_core.dart'
-    show CompletionRequest;
-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/completion_core.dart';
-import 'package:analyzer/file_system/file_system.dart';
-import 'package:analyzer/src/context/context.dart'
-    show AnalysisFutureHelper, AnalysisContextImpl;
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/engine.dart' hide AnalysisContextImpl;
-import 'package:analyzer/src/generated/source.dart';
-import 'package:analyzer/src/task/dart.dart';
-import 'package:analyzer/task/dart.dart';
-
-/**
- * The information about a requested list of completions within a Dart file.
- */
-class DartCompletionRequestImpl extends CompletionRequestImpl
-    implements DartCompletionRequest {
-  /**
-   * The cached completion target or `null` if not computed yet.
-   */
-  CompletionTarget _target;
-
-  /**
-   * `true` if [resolveDeclarationsInScope] has partially resolved the unit
-   * referenced by [target], else `false`.
-   */
-  bool _haveResolveDeclarationsInScope = false;
-
-  /**
-   * Initialize a newly created completion request based on the given request.
-   */
-  factory DartCompletionRequestImpl.forRequest(CompletionRequest request) {
-    return new DartCompletionRequestImpl._(request.context,
-        request.resourceProvider, request.source, request.offset);
-  }
-
-  DartCompletionRequestImpl._(AnalysisContext context,
-      ResourceProvider resourceProvider, Source source, int offset)
-      : super(context, resourceProvider, source, offset);
-
-  @override
-  Future<CompilationUnit> resolveDeclarationsInScope() async {
-    CompilationUnit unit = target.unit;
-    if (_haveResolveDeclarationsInScope) {
-      return unit;
-    }
-
-    // Determine the library source
-    Source librarySource;
-    if (unit.directives.any((d) => d is PartOfDirective)) {
-      List<Source> libraries = context.getLibrariesContaining(source);
-      if (libraries.isEmpty) {
-        return null;
-      }
-      librarySource = libraries[0];
-    } else {
-      librarySource = source;
-    }
-
-    // Resolve declarations in the target unit
-    CompilationUnit resolvedUnit =
-        await new AnalysisFutureHelper<CompilationUnit>(
-            context,
-            new LibrarySpecificUnit(librarySource, source),
-            RESOLVED_UNIT3).computeAsync();
-
-    // TODO(danrubel) determine if the underlying source has been modified
-    // in a way that invalidates the completion request
-    // and return null
-
-    // Gracefully degrade if unit cannot be resolved
-    if (resolvedUnit == null) {
-      return null;
-    }
-
-    // Recompute the target for the newly resolved unit
-    _target = new CompletionTarget.forOffset(resolvedUnit, offset);
-    _haveResolveDeclarationsInScope = true;
-    return resolvedUnit;
-  }
-
-  @override
-  CompletionTarget get target {
-    if (_target == null) {
-      CompilationUnit unit = context.computeResult(source, PARSED_UNIT);
-      _target = new CompletionTarget.forOffset(unit, offset);
-    }
-    return _target;
-  }
-}