Rework contribution sorter to use futures

pkg/analysis_server/lib/src/services/completion/common_usage_computer.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.relevance;
-
-import 'package:analysis_server/src/protocol_server.dart' as protocol;
-import 'package:analysis_server/src/protocol_server.dart'
-    show CompletionSuggestion, CompletionSuggestionKind;
-import 'package:analysis_server/src/provisional/completion/completion_core.dart';
-import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
-import 'package:analysis_server/src/services/completion/contribution_sorter.dart';
-import 'package:analysis_server/src/services/completion/dart_completion_manager.dart'
-    show DART_RELEVANCE_COMMON_USAGE;
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/element.dart';
-import 'package:analyzer/src/task/dart.dart';
-import 'package:analyzer/task/dart.dart';
-
-part 'common_usage_generated.dart';
-
-/**
- * A computer for adjusting the relevance of completions computed by others
- * based upon common Dart usage patterns. This is a long-lived object
- * that should not maintain state between calls to it's [sort] method.
- */
-class CommonUsageComputer implements ContributionSorter {
-  /**
-   * A map of <library>.<classname> to an ordered list of method names,
-   * field names, getter names, and named constructors.
-   * The names are ordered from most relevant to least relevant.
-   * Names not listed are considered equally less relevant than those listed.
-   */
-  Map<String, List<String>> selectorRelevance;
-
-  CommonUsageComputer([this.selectorRelevance = defaultSelectorRelevance]);
-
-  @override
-  AnalysisRequest sort(CompletionRequest request,
-      Iterable<CompletionSuggestion> suggestions) {
-    _update(request, suggestions);
-    return null;
-  }
-
-  CompletionTarget _getCompletionTarget(CompletionRequest request) {
-    // TODO (danrubel) get cached completion target
-    var libSrcs = request.context.getLibrariesContaining(request.source);
-    if (libSrcs.length == 0) {
-      return null;
-    }
-    var libElem = request.context.getResult(libSrcs[0], LIBRARY_ELEMENT1);
-    if (libElem is LibraryElement) {
-      var unit = request.context.getResult(
-          new LibrarySpecificUnit(libElem.source, request.source),
-          RESOLVED_UNIT3);
-      if (unit is CompilationUnit) {
-        return new CompletionTarget.forOffset(unit, request.offset);
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Adjusts the relevance based on the given completion context.
-   * The compilation unit and completion node
-   * in the given completion context may not be resolved.
-   */
-  void _update(
-      CompletionRequest request, Iterable<CompletionSuggestion> suggestions) {
-    var target = _getCompletionTarget(request);
-    if (target != null) {
-      var visitor = new _BestTypeVisitor(target.entity);
-      DartType type = target.containingNode.accept(visitor);
-      if (type != null) {
-        Element typeElem = type.element;
-        if (typeElem != null) {
-          LibraryElement libElem = typeElem.library;
-          if (libElem != null) {
-            _updateInvocationRelevance(type, libElem, suggestions);
-          }
-        }
-      }
-    }
-  }
-
-  /**
-   * Adjusts the relevance of all method suggestions based upon the given
-   * target type and library.
-   */
-  void _updateInvocationRelevance(DartType type, LibraryElement libElem,
-      Iterable<CompletionSuggestion> suggestions) {
-    String typeName = type.name;
-    List<String> selectors = selectorRelevance['${libElem.name}.${typeName}'];
-    if (selectors != null) {
-      for (CompletionSuggestion suggestion in suggestions) {
-        protocol.Element element = suggestion.element;
-        if (element != null &&
-            (element.kind == protocol.ElementKind.CONSTRUCTOR ||
-                element.kind == protocol.ElementKind.FIELD ||
-                element.kind == protocol.ElementKind.GETTER ||
-                element.kind == protocol.ElementKind.METHOD ||
-                element.kind == protocol.ElementKind.SETTER) &&
-            suggestion.kind == CompletionSuggestionKind.INVOCATION &&
-            suggestion.declaringType == typeName) {
-          int index = selectors.indexOf(suggestion.completion);
-          if (index != -1) {
-            suggestion.relevance = DART_RELEVANCE_COMMON_USAGE - index;
-          }
-        }
-      }
-    }
-  }
-}
-
-/**
- * An [AstVisitor] used to determine the best defining type of a node.
- */
-class _BestTypeVisitor extends GeneralizingAstVisitor {
-  /**
-   * The entity which the completed text will replace (or which will be
-   * displaced once the completed text is inserted).  This may be an AstNode or
-   * a Token, or it may be null if the cursor is after all tokens in the file.
-   * See field of the same name in [CompletionTarget].
-   */
-  final Object entity;
-
-  _BestTypeVisitor(this.entity);
-
-  DartType visitConstructorName(ConstructorName node) {
-    if (node.period != null && node.name == entity) {
-      TypeName typeName = node.type;
-      if (typeName != null) {
-        return typeName.type;
-      }
-    }
-    return null;
-  }
-
-  DartType visitNode(AstNode node) {
-    return null;
-  }
-
-  DartType visitPrefixedIdentifier(PrefixedIdentifier node) {
-    if (node.identifier == entity) {
-      SimpleIdentifier prefix = node.prefix;
-      if (prefix != null) {
-        return prefix.bestType;
-      }
-    }
-    return null;
-  }
-
-  DartType visitPropertyAccess(PropertyAccess node) {
-    if (node.propertyName == entity) {
-      Expression target = node.realTarget;
-      if (target != null) {
-        return target.bestType;
-      }
-    }
-    return null;
-  }
-}