return correct replacementOffset and replacementLength

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

 // Copyright (c) 2014, 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 test.services.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
-import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analysis_server/src/services/completion/imported_type_computer.dart';
 import 'package:analysis_server/src/services/completion/invocation_computer.dart';
 import 'package:analysis_server/src/services/completion/keyword_computer.dart';
 import 'package:analysis_server/src/services/completion/local_computer.dart';
+import 'package:analysis_server/src/services/search/search_engine.dart';
 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/source.dart';
 
 /**
  * The base class for computing code completion suggestions.
  */
 abstract class DartCompletionComputer {
   /**
@@ skipping 40 matching lines @@
   }
 
   /**
    * Compute suggestions based upon cached information only
    * then send an initial response to the client.
    */
   void computeFast() {
     CompilationUnit unit = context.parseCompilationUnit(source);
     request.unit = unit;
     request.node = new NodeLocator.con1(offset).searchWithin(unit);
+    if (request.node != null) {
+      request.node.accept(new _ReplacementOffsetBuilder(request));
+    }
     computers.removeWhere((DartCompletionComputer c) => c.computeFast(request));
     sendResults(computers.isEmpty);
   }
 
   /**
    * If there is remaining work to be done, then wait for the unit to be
    * resolved and request that each remaining computer finish their work.
    */
   void computeFull() {
     waitForAnalysis().then((CompilationUnit unit) {
@@ skipping 26 matching lines @@
           new ImportedTypeComputer(),
           new InvocationComputer()];
     }
   }
 
   /**
    * Send the current list of suggestions to the client.
    */
   void sendResults(bool last) {
     controller.add(
-        new CompletionResult(request.offset, 0, request.suggestions, last));
+        new CompletionResult(
+            request.replacementOffset,
+            request.replacementLength,
+            request.suggestions,
+            last));
     if (last) {
       controller.close();
     }
   }
 
   /**
    * Return a future that completes when analysis is complete.
    * Return `true` if the compilation unit is be resolved.
    */
   Future<CompilationUnit> waitForAnalysis() {
@@ skipping 42 matching lines @@
   CompilationUnit unit;
 
   /**
    * The node in which the completion occurred. This node
    * may or may not be resolved when [DartCompletionComputer.computeFast]
    * is called but is resolved when [DartCompletionComputer.computeFull].
    */
   AstNode node;
 
   /**
+   * The offset of the start of the text to be replaced.
+   * This will be different than the offset used to request the completion
+   * suggestions if there was a portion of an identifier before the original
+   * offset. In particular, the replacementOffset will be the offset of the
+   * beginning of said identifier.
+   */
+  int replacementOffset;
+
+  /**
+   * The length of the text to be replaced if the remainder of the identifier
+   * containing the cursor is to be replaced when the suggestion is applied
+   * (that is, the number of characters in the existing identifier).
+   */
+  int replacementLength;
+
+  /**
    * The list of suggestions to be sent to the client.
    */
   final List<CompletionSuggestion> suggestions = [];
 
   DartCompletionRequest(this.context, this.searchEngine, this.source,
       this.offset);
 }
+
+/**
+ * Visitor used to determine the replacement offset and length
+ * based upon the cursor location.
+ */
+class _ReplacementOffsetBuilder extends SimpleAstVisitor {
+  final DartCompletionRequest request;
+
+  _ReplacementOffsetBuilder(this.request) {
+    request.replacementOffset = request.offset;
+    request.replacementLength = 0;
+  }
+
+  visitSimpleIdentifier(SimpleIdentifier node) {
+    request.replacementOffset = node.offset;
+    request.replacementLength = node.length;
+  }
+}