Avoid analysis server crash when reanalyze invoked during analysis.

pkg/analysis_server/test/integration/analysis/reanalyze_concurrent_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 test verifies that if reanalysis is performed while reanalysis is in
+ * progress, no problems occur.  See dartbug.com/21448.
+ */
+library test.integration.analysis.reanalyze_concurrent;
+
+import 'dart:async';
+
+import 'package:analysis_server/src/protocol.dart';
+import 'package:unittest/unittest.dart';
+
+import '../../reflective_tests.dart';
+import '../integration_tests.dart';
+
+@ReflectiveTestCase()
+class Test extends AbstractAnalysisServerIntegrationTest {
+  test_reanalyze_concurrent() {
+    String pathname = sourcePath('test.dart');
+    String text = '''
+// Do a bunch of imports so that analysis has some work to do.
+import 'dart:io';
+import 'dart:convert';
+import 'dart:async';
+
+main() {}''';
+    writeFile(pathname, text);
+    standardAnalysisSetup();
+    return analysisFinished.then((_) {
+      sendAnalysisReanalyze();
+      // Wait for reanalysis to start.
+      return onServerStatus.first.then((_) {
+        sendAnalysisReanalyze();
+        return analysisFinished.then((_) {
+          // Now that reanalysis has finished, no further analysis should occur.
+          onServerStatus.listen((ServerStatusParams data) {
+            if (data.analysis != null) {
+              if (data.analysis.isAnalyzing) {
+                // Most likely what happened is that the first reanalyze
+                // completed before the second reanalyze had a chance to start,
+                // and we are just now starting the second reanalyze.  If this is
+                // the case, then the test isn't testing what it's meant to test
+                // (because we are trying to test what happens when one reanalyze
+                // starts while another is in progress).  In which case we will
+                // need to give the analyzer more work to do.
+                fail('First reanalyze finished before second started.');
+              }
+            }
+          });
+          // Give the server an extra second to make sure it doesn't take any
+          // more actions.
+          return new Future.delayed(new Duration(seconds: 1));
+        });
+      });
+    });
+  }
+}
+
+main() {
+  runReflectiveTests(Test);
+}