update code completion suggestion relevance based on common usage

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

Index: pkg/analysis_server/lib/src/services/completion/common_usage_computer.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/common_usage_computer.dart b/pkg/analysis_server/lib/src/services/completion/common_usage_computer.dart
new file mode 100644
index 0000000000000000000000000000000000000000..5c7d340b41e455d09dbfb5dddc25dd31da455629
--- /dev/null
+++ b/pkg/analysis_server/lib/src/services/completion/common_usage_computer.dart
@@ -0,0 +1,160 @@
+// 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/services/completion/dart_completion_manager.dart';
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/element.dart';
+
+/**
+ * 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.
+ */
+const Map<String, List<String>> defaultSelectorRelevance = const {//
+// Sample implementation which updates the relevance of the following
+//     new Random().nextInt(...)
+//     new Random().nextDouble(...)
+//     new Random().nextBool() - not commonly used thus omitted from list
+// Entries should look something like this
+//     'dart.math.Random': const ['nextInt', 'nextDouble'],
+//     'dart.async.Future': const ['value', 'wait'],
+};
+
+/**
+ * A computer for adjusting the relevance of completions computed by others
+ * based upon common Dart usage patterns.
+ */
+class CommonUsageComputer {
+  /**
+   * 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]);
+
+  /**
+   * Adjusts the relevance based on the given completion context.
+   * The compilation unit and completion node
+   * in the given completion context may not be resolved.
+   * This method should execute quickly and not block waiting for any analysis.
+   */
+  void computeFast(DartCompletionRequest request) {
+    _update(request);
+  }
+
+  /**
+   * Adjusts the relevance based on the given completion context.
+   * The compilation unit and completion node
+   * in the given completion context are resolved.
+   */
+  void computeFull(DartCompletionRequest request) {
+    _update(request);
+  }
+
+  /**
+   * 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(DartCompletionRequest request) {
+    var visitor = new _BestTypeVisitor(request.target.entity);
+    DartType type = request.target.containingNode.accept(visitor);
+    if (type != null) {
+      Element typeElem = type.element;
+      if (typeElem != null) {
+        LibraryElement libElem = typeElem.library;
+        if (libElem != null) {
+          _updateInvocationRelevance(request, type, libElem);
+        }
+      }
+    }
+  }
+
+  /**
+   * Adjusts the relevance of all method suggestions based upon the given
+   * target type and library.
+   */
+  void _updateInvocationRelevance(DartCompletionRequest request, DartType type,
+      LibraryElement libElem) {
+    String typeName = type.name;
+    List<String> selectors = selectorRelevance['${libElem.name}.${typeName}'];
+    if (selectors != null) {
+      for (CompletionSuggestion suggestion in request.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;
+  }
+}