Port two completion contributors for use by plugins

pkg/analyzer_plugin/lib/utilities/completion/type_member_contributor.dart

+// Copyright (c) 2017, 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.
+
+import 'dart:async';
+import 'dart:collection';
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart' hide Element;
+import 'package:analyzer_plugin/src/utilities/completion/completion_target.dart';
+import 'package:analyzer_plugin/src/utilities/completion/suggestion_builder.dart';
+import 'package:analyzer_plugin/src/utilities/visitors/local_declaration_visitor.dart';
+import 'package:analyzer_plugin/utilities/completion/completion_core.dart';
+import 'package:analyzer_plugin/utilities/completion/relevance.dart';
+import 'package:analyzer_plugin/utilities/completion/suggestion_builder.dart';
+
+/**
+ * A completion contributor that will generate suggestions for instance
+ * invocations and accesses.
+ */
+class TypeMemberContributor implements CompletionContributor {
+  @override
+  Future<Null> computeSuggestions(
+      CompletionRequest request, CompletionCollector collector) async {
+    LibraryElement containingLibrary = request.result.libraryElement;
+    // Gracefully degrade if the library element is not resolved
+    // e.g. detached part file or source change
+    if (containingLibrary == null) {
+      return;
+    }
+
+    // Recompute the target since resolution may have changed it
+    Expression expression = _computeDotTarget(request);
+    if (expression == null || expression.isSynthetic) {
+      return;
+    }
+    if (expression is Identifier) {
+      Element element = expression.bestElement;
+      if (element is ClassElement) {
+        // Suggestions provided by StaticMemberContributor
+        return;
+      }
+      if (element is PrefixElement) {
+        // Suggestions provided by LibraryMemberContributor
+        return;
+      }
+    }
+
+    // Determine the target expression's type
+    DartType type = expression.bestType;
+    if (type.isDynamic) {
+      // If the expression does not provide a good type
+      // then attempt to get a better type from the element
+      if (expression is Identifier) {
+        Element elem = expression.bestElement;
+        if (elem is FunctionTypedElement) {
+          type = elem.returnType;
+        } else if (elem is ParameterElement) {
+          type = elem.type;
+        } else if (elem is LocalVariableElement) {
+          type = elem.type;
+        }
+        if ((type == null || type.isDynamic) &&
+            expression is SimpleIdentifier) {
+          // If the element does not provide a good type
+          // then attempt to get a better type from a local declaration
+          _LocalBestTypeVisitor visitor =
+              new _LocalBestTypeVisitor(expression.name, request.offset);
+          if (visitor.visit(expression) && visitor.typeFound != null) {
+            type = visitor.typeFound;
+          }
+        }
+      }
+    }
+    String containingMethodName;
+    if (expression is SuperExpression && type is InterfaceType) {
+      // Suggest members from superclass if target is "super"
+      type = (type as InterfaceType).superclass;
+      // Determine the name of the containing method because
+      // the most likely completion is a super expression with same name
+      MethodDeclaration containingMethod =
+          expression.getAncestor((p) => p is MethodDeclaration);
+      if (containingMethod != null) {
+        SimpleIdentifier id = containingMethod.name;
+        if (id != null) {
+          containingMethodName = id.name;
+        }
+      }
+    }
+    if (type.isDynamic) {
+      // Suggest members from object if target is "dynamic"
+      type = request.result.typeProvider.objectType;
+    }
+
+    // Build the suggestions
+    if (type is InterfaceType) {
+      _SuggestionBuilder builder = new _SuggestionBuilder(
+          request.resourceProvider, collector, containingLibrary);
+      builder.buildSuggestions(type, containingMethodName);
+    }
+  }
+
+  /**
+   * Update the completion [target] and [dotTarget] based on the given [unit].
+   */
+  Expression _computeDotTarget(CompletionRequest request) {
+    CompletionTarget target =
+        new CompletionTarget.forOffset(request.result.unit, request.offset);
+    AstNode node = target.containingNode;
+    if (node is MethodInvocation) {
+      if (identical(node.methodName, target.entity)) {
+        return node.realTarget;
+      } else if (node.isCascaded && node.operator.offset + 1 == target.offset) {
+        return node.realTarget;
+      }
+    }
+    if (node is PropertyAccess) {
+      if (identical(node.propertyName, target.entity)) {
+        return node.realTarget;
+      } else if (node.isCascaded && node.operator.offset + 1 == target.offset) {
+        return node.realTarget;
+      }
+    }
+    if (node is PrefixedIdentifier) {
+      if (identical(node.identifier, target.entity)) {
+        return node.prefix;
+      }
+    }
+    return null;
+  }
+}
+
+/**
+ * An [AstVisitor] which looks for a declaration with the given name
+ * and if found, tries to determine a type for that declaration.
+ */
+class _LocalBestTypeVisitor extends LocalDeclarationVisitor {
+  /**
+   * The name for the declaration to be found.
+   */
+  final String targetName;
+
+  /**
+   * The best type for the found declaration,
+   * or `null` if no declaration found or failed to determine a type.
+   */
+  DartType typeFound;
+
+  /**
+   * Construct a new instance to search for a declaration
+   */
+  _LocalBestTypeVisitor(this.targetName, int offset) : super(offset);
+
+  @override
+  void declaredClass(ClassDeclaration declaration) {
+    if (declaration.name.name == targetName) {
+      // no type
+      finished();
+    }
+  }
+
+  @override
+  void declaredClassTypeAlias(ClassTypeAlias declaration) {
+    if (declaration.name.name == targetName) {
+      // no type
+      finished();
+    }
+  }
+
+  @override
+  void declaredField(FieldDeclaration fieldDecl, VariableDeclaration varDecl) {
+    if (varDecl.name.name == targetName) {
+      // Type provided by the element in computeFull above
+      finished();
+    }
+  }
+
+  @override
+  void declaredFunction(FunctionDeclaration declaration) {
+    if (declaration.name.name == targetName) {
+      TypeAnnotation typeName = declaration.returnType;
+      if (typeName != null) {
+        typeFound = typeName.type;
+      }
+      finished();
+    }
+  }
+
+  @override
+  void declaredFunctionTypeAlias(FunctionTypeAlias declaration) {
+    if (declaration.name.name == targetName) {
+      TypeAnnotation typeName = declaration.returnType;
+      if (typeName != null) {
+        typeFound = typeName.type;
+      }
+      finished();
+    }
+  }
+
+  @override
+  void declaredLabel(Label label, bool isCaseLabel) {
+    if (label.label.name == targetName) {
+      // no type
+      finished();
+    }
+  }
+
+  @override
+  void declaredLocalVar(SimpleIdentifier name, TypeAnnotation type) {
+    if (name.name == targetName) {
+      typeFound = name.bestType;
+      finished();
+    }
+  }
+
+  @override
+  void declaredMethod(MethodDeclaration declaration) {
+    if (declaration.name.name == targetName) {
+      TypeAnnotation typeName = declaration.returnType;
+      if (typeName != null) {
+        typeFound = typeName.type;
+      }
+      finished();
+    }
+  }
+
+  @override
+  void declaredParam(SimpleIdentifier name, TypeAnnotation type) {
+    if (name.name == targetName) {
+      // Type provided by the element in computeFull above
+      finished();
+    }
+  }
+
+  @override
+  void declaredTopLevelVar(
+      VariableDeclarationList varList, VariableDeclaration varDecl) {
+    if (varDecl.name.name == targetName) {
+      // Type provided by the element in computeFull above
+      finished();
+    }
+  }
+}
+
+/**
+ * This class provides suggestions based upon the visible instance members in
+ * an interface type.
+ */
+class _SuggestionBuilder {
+  /**
+   * Enumerated value indicating that we have not generated any completions for
+   * a given identifier yet.
+   */
+  static const int _COMPLETION_TYPE_NONE = 0;
+
+  /**
+   * Enumerated value indicating that we have generated a completion for a
+   * getter.
+   */
+  static const int _COMPLETION_TYPE_GETTER = 1;
+
+  /**
+   * Enumerated value indicating that we have generated a completion for a
+   * setter.
+   */
+  static const int _COMPLETION_TYPE_SETTER = 2;
+
+  /**
+   * Enumerated value indicating that we have generated a completion for a
+   * field, a method, or a getter/setter pair.
+   */
+  static const int _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET = 3;
+
+  /**
+   * The resource provider used to access the file system.
+   */
+  final ResourceProvider resourceProvider;
+
+  /**
+   * The collector being used to collect completion suggestions.
+   */
+  final CompletionCollector collector;
+
+  /**
+   * The library containing the unit in which the completion is requested.
+   */
+  final LibraryElement containingLibrary;
+
+  /**
+   * Map indicating, for each possible completion identifier, whether we have
+   * already generated completions for a getter, setter, or both.  The "both"
+   * case also handles the case where have generated a completion for a method
+   * or a field.
+   *
+   * Note: the enumerated values stored in this map are intended to be bitwise
+   * compared.
+   */
+  Map<String, int> _completionTypesGenerated = new HashMap<String, int>();
+
+  /**
+   * Map from completion identifier to completion suggestion
+   */
+  Map<String, CompletionSuggestion> _suggestionMap =
+      <String, CompletionSuggestion>{};
+
+  /**
+   * The builder used to build suggestions.
+   */
+  final SuggestionBuilder builder;
+
+  _SuggestionBuilder(
+      this.resourceProvider, this.collector, this.containingLibrary)
+      : builder = new SuggestionBuilderImpl(resourceProvider);
+
+  Iterable<CompletionSuggestion> get suggestions => _suggestionMap.values;
+
+  /**
+   * Create completion suggestions for 'dot' completions on the given [type].
+   * If the 'dot' completion is a super expression, then [containingMethodName]
+   * is the name of the method in which the completion is requested.
+   */
+  void buildSuggestions(InterfaceType type, String containingMethodName) {
+    // Visit all of the types in the class hierarchy, collecting possible
+    // completions.  If multiple elements are found that complete to the same
+    // identifier, addSuggestion will discard all but the first (with a few
+    // exceptions to handle getter/setter pairs).
+    List<InterfaceType> types = _getTypeOrdering(type);
+    for (InterfaceType targetType in types) {
+      for (MethodElement method in targetType.methods) {
+        // Exclude static methods when completion on an instance
+        if (!method.isStatic) {
+          // Boost the relevance of a super expression
+          // calling a method of the same name as the containing method
+          _addSuggestion(method,
+              relevance: method.name == containingMethodName
+                  ? DART_RELEVANCE_HIGH
+                  : null);
+        }
+      }
+      for (PropertyAccessorElement propertyAccessor in targetType.accessors) {
+        if (!propertyAccessor.isStatic) {
+          if (propertyAccessor.isSynthetic) {
+            // Avoid visiting a field twice
+            if (propertyAccessor.isGetter) {
+              _addSuggestion(propertyAccessor.variable);
+            }
+          } else {
+            _addSuggestion(propertyAccessor);
+          }
+        }
+      }
+    }
+    for (CompletionSuggestion suggestion in suggestions) {
+      collector.addSuggestion(suggestion);
+    }
+  }
+
+  /**
+   * Add a suggestion based upon the given element, provided that it is not
+   * shadowed by a previously added suggestion.
+   */
+  void _addSuggestion(Element element, {int relevance}) {
+    if (element.isPrivate) {
+      if (element.library != containingLibrary) {
+        // Do not suggest private members for imported libraries
+        return;
+      }
+    }
+    String identifier = element.displayName;
+
+    if (relevance == null) {
+      // Decrease relevance of suggestions starting with $
+      // https://github.com/dart-lang/sdk/issues/27303
+      if (identifier != null && identifier.startsWith(r'$')) {
+        relevance = DART_RELEVANCE_LOW;
+      } else {
+        relevance = DART_RELEVANCE_DEFAULT;
+      }
+    }
+
+    int alreadyGenerated = _completionTypesGenerated.putIfAbsent(
+        identifier, () => _COMPLETION_TYPE_NONE);
+    if (element is MethodElement) {
+      // Anything shadows a method.
+      if (alreadyGenerated != _COMPLETION_TYPE_NONE) {
+        return;
+      }
+      _completionTypesGenerated[identifier] =
+          _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
+    } else if (element is PropertyAccessorElement) {
+      if (element.isGetter) {
+        // Getters, fields, and methods shadow a getter.
+        if ((alreadyGenerated & _COMPLETION_TYPE_GETTER) != 0) {
+          return;
+        }
+        _completionTypesGenerated[identifier] |= _COMPLETION_TYPE_GETTER;
+      } else {
+        // Setters, fields, and methods shadow a setter.
+        if ((alreadyGenerated & _COMPLETION_TYPE_SETTER) != 0) {
+          return;
+        }
+        _completionTypesGenerated[identifier] |= _COMPLETION_TYPE_SETTER;
+      }
+    } else if (element is FieldElement) {
+      // Fields and methods shadow a field.  A getter/setter pair shadows a
+      // field, but a getter or setter by itself doesn't.
+      if (alreadyGenerated == _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET) {
+        return;
+      }
+      _completionTypesGenerated[identifier] =
+          _COMPLETION_TYPE_FIELD_OR_METHOD_OR_GETSET;
+    } else {
+      // Unexpected element type; skip it.
+      assert(false);
+      return;
+    }
+    CompletionSuggestion suggestion =
+        builder.forElement(element, relevance: relevance);
+    if (suggestion != null) {
+      _suggestionMap[suggestion.completion] = suggestion;
+    }
+  }
+
+  /**
+   * Get a list of [InterfaceType]s that should be searched to find the
+   * possible completions for an object having type [type].
+   */
+  List<InterfaceType> _getTypeOrdering(InterfaceType type) {
+    // Candidate completions can come from [type] as well as any types above it
+    // in the class hierarchy (including mixins, superclasses, and interfaces).
+    // If a given completion identifier shows up in multiple types, we should
+    // use the element that is nearest in the superclass chain, so we will
+    // visit [type] first, then its mixins, then its superclass, then its
+    // superclass's mixins, etc., and only afterwards visit interfaces.
+    //
+    // We short-circuit loops in the class hierarchy by keeping track of the
+    // classes seen (not the interfaces) so that we won't be fooled by nonsense
+    // like "class C<T> extends C<List<T>> {}"
+    List<InterfaceType> result = <InterfaceType>[];
+    Set<ClassElement> classesSeen = new HashSet<ClassElement>();
+    List<InterfaceType> typesToVisit = <InterfaceType>[type];
+    while (typesToVisit.isNotEmpty) {
+      InterfaceType nextType = typesToVisit.removeLast();
+      if (!classesSeen.add(nextType.element)) {
+        // Class had already been seen, so ignore this type.
+        continue;
+      }
+      result.add(nextType);
+      // typesToVisit is a stack, so push on the interfaces first, then the
+      // superclass, then the mixins.  This will ensure that they are visited
+      // in the reverse order.
+      typesToVisit.addAll(nextType.interfaces);
+      if (nextType.superclass != null) {
+        typesToVisit.add(nextType.superclass);
+      }
+      typesToVisit.addAll(nextType.mixins);
+    }
+    return result;
+  }
+}