Introduce CompletionTarget to take the place of the Node being completed.

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 services.completion.dart;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/services/completion/arglist_computer.dart';
 import 'package:analysis_server/src/services/completion/combinator_computer.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
+import 'package:analysis_server/src/services/completion/completion_target.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
 import 'package:analysis_server/src/services/completion/imported_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/completion/optype.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
@@ skipping 67 matching lines @@
    * Compute suggestions based upon cached information only
    * then send an initial response to the client.
    * Return a list of computers for which [computeFull] should be called
    */
   List<DartCompletionComputer> computeFast(DartCompletionRequest request) {
     return request.performance.logElapseTime('computeFast', () {
       CompilationUnit unit = context.parseCompilationUnit(source);
       request.unit = unit;
       request.node = new NodeLocator.con1(request.offset).searchWithin(unit);
       request.node.accept(new _ReplacementOffsetBuilder(request));
+      request.target = new CompletionTarget.forOffset(unit, request.offset);
       List<DartCompletionComputer> todo = new List.from(computers);
       todo.removeWhere((DartCompletionComputer c) {
         return request.performance.logElapseTime(
             'computeFast ${c.runtimeType}',
             () {
           return c.computeFast(request);
         });
       });
       sendResults(request, todo.isEmpty);
       return todo;
@@ skipping 12 matching lines @@
         return;
       }
       request.performance.logElapseTime('waitForAnalysis');
       if (unit == null) {
         sendResults(request, true);
         return;
       }
       request.performance.logElapseTime('computeFull', () {
         request.unit = unit;
         request.node = new NodeLocator.con1(request.offset).searchWithin(unit);
+        // TODO(paulberry): Do we need to invoke _ReplacementOffsetBuilder
+        // again?
+        request.target = new CompletionTarget.forOffset(unit, request.offset);
         int count = todo.length;
         todo.forEach((DartCompletionComputer c) {
           String name = c.runtimeType.toString();
           String completeTag = 'computeFull $name complete';
           request.performance.logStartTime(completeTag);
           request.performance.logElapseTime('computeFull $name', () {
             c.computeFull(request).then((bool changed) {
               request.performance.logElapseTime(completeTag);
               bool last = --count == 0;
               if (changed || last) {
@@ skipping 89 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 completion target.  This determines what part of the parse tree
+   * will receive the newly inserted text.
+   *
+   * TODO(paulberry) gradually transition code over to using this rather than
+   * [node].
+   */
+  CompletionTarget target;
+
+  /**
    * Information about the types of suggestions that should be included.
    */
   OpType _optype;
 
   /**
    * 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.
@@ skipping 20 matching lines @@
    * Return the original text from the [replacementOffset] to the [offset]
    * that can be used to filter the suggestions on the server side.
    */
   String get filterText {
     return context.getContents(
         source).data.substring(replacementOffset, offset);
   }
 
   /**
    * Information about the types of suggestions that should be included.
-   * This will return `null` if the [node] has not been set.
+   * The [target] must be set first.
    */
   OpType get optype {
-    if (_optype == null && node != null) {
-      _optype = new OpType.forCompletion(node, offset);
+    if (_optype == null) {
+      _optype = new OpType.forCompletion(target, offset);
     }
     return _optype;
   }
 }
 
 /**
  * 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;
   }
 }