Make futures returned by AnalysisContext cancelable.

pkg/analyzer/test/generated/engine_test.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine.engine_test;
 
 import 'dart:async';
 import 'dart:collection';
 
+import 'package:analyzer/src/cancelable_future.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/constant.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/html.dart' as ht;
 import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/java_engine.dart';
 import 'package:analyzer/src/generated/java_engine_io.dart';
 import 'package:analyzer/src/generated/parser.dart';
@@ skipping 1122 matching lines @@
       completed = true;
     });
     return pumpEventQueue().then((_) {
       expect(completed, isFalse);
       while (_context.performAnalysisTask().hasMoreWork) {}
     }).then((_) => pumpEventQueue()).then((_) {
       expect(completed, isTrue);
     });
   }
 
+  Future test_getResolvedCompilationUnitFuture_cancel() {
+    _context = AnalysisContextFactory.contextWithCore();
+    _sourceFactory = _context.sourceFactory;
+    Source source = _addSource("/lib.dart", "library lib;");
+    // Complete all pending analysis tasks and flush the AST so that it won't
+    // be available immediately.
+    while (_context.performAnalysisTask().hasMoreWork) {}

[Brian Wilkerson, 2014/12/15 19:49:26]

We have normally put in some limit on the number of times we will invoke
performAnalysisTask before failing in order to guard against infinite loops.

[Paul Berry, 2014/12/16 16:58:06]

Done.

+    DartEntry dartEntry = _context.getReadableSourceEntryOrNull(source);
+    dartEntry.flushAstStructures();
+    CancelableFuture<CompilationUnit> future =
+        _context.getResolvedCompilationUnitFuture(source, source);
+    bool completed = false;
+    future.then((CompilationUnit unit) {
+      fail('Future should have been canceled');
+    }, onError: (error) {
+      expect(error, new isInstanceOf<FutureCanceledError>());
+      completed = true;
+    });
+    expect(completed, isFalse);
+    expect(_context.pendingFutureSources_forTesting, isNotEmpty);
+    future.cancel();
+    expect(_context.pendingFutureSources_forTesting, isEmpty);
+    return pumpEventQueue().then((_) {
+      expect(completed, isTrue);
+      expect(_context.pendingFutureSources_forTesting, isEmpty);
+    });
+  }
+
   Future test_getResolvedCompilationUnitFuture_unrelatedLibrary() {
     _context = AnalysisContextFactory.contextWithCore();
     _sourceFactory = _context.sourceFactory;
     Source librarySource = _addSource("/lib.dart", "library lib;");
     Source partSource = _addSource("/part.dart", "part of foo;");
     bool completed = false;
     _context.getResolvedCompilationUnitFuture(
         partSource,
         librarySource).then((_) {
       fail('Expected resolution to fail');
@@ skipping 5889 matching lines @@
   bool contains(Source source) => source == libB;
 }
 
 
 class _UniversalCachePartitionTest_test_setMaxCacheSize implements
     CacheRetentionPolicy {
   @override
   RetentionPriority getAstPriority(Source source, SourceEntry sourceEntry) =>
       RetentionPriority.LOW;
 }