Send responses for any pending 'analysis.getErrors' requests during context removal.

pkg/analysis_server/lib/src/analysis_server.dart

Index: pkg/analysis_server/lib/src/analysis_server.dart
diff --git a/pkg/analysis_server/lib/src/analysis_server.dart b/pkg/analysis_server/lib/src/analysis_server.dart
index 285e82ff8cbfd104ffe69cedcd6e1667301da125..62beafe4b3bdf819f7401bf281090258051127a8 100644
--- a/pkg/analysis_server/lib/src/analysis_server.dart
+++ b/pkg/analysis_server/lib/src/analysis_server.dart
@@ -56,13 +56,20 @@ class AnalysisServerContextDirectoryManager extends ContextDirectoryManager {
   @override
   void applyChangesToContext(Folder contextFolder, ChangeSet changeSet) {
     AnalysisContext context = analysisServer.folderMap[contextFolder];
-    context.applyChanges(changeSet);
-    analysisServer.schedulePerformAnalysisOperation(context);
+    if (context != null) {

[Paul Berry, 2014/07/23 15:06:51]

This check shouldn't be necessary.  The caller will only call
applyChangesToContext() on folders that have an associated context.

[scheglov, 2014/07/24 16:54:04]

We need this in case if "folder removed" watch event happens before some "file
changed" event.
I trigger this situation in the test, because I remove the context before events
for "addFile" are handled.

[Paul Berry, 2014/07/24 17:32:04]

I believe this won't ever happen in production code, and is unnecessary to unit
test for.  If you look at ContextDirectoryManager._destroyContext(), it cancels
the subscription that is watching for "file changed" events before calling
removeContext().  

But I guess I'm ok with leaving this check in as defensive coding.

+      context.applyChanges(changeSet);
+      analysisServer.schedulePerformAnalysisOperation(context);
+    }
   }
 
   @override
   void removeContext(Folder folder) {
-    analysisServer.folderMap.remove(folder);
+    AnalysisContext context = analysisServer.folderMap.remove(folder);
+    if (context != null) {

[Paul Berry, 2014/07/23 15:06:51]

Similar situation with this check.

[scheglov, 2014/07/24 16:54:03]

OK

I think we can trust watcher that it won't tell us about removing the same
folder twice unless if it was recreated, so that there is also a corresponding
AnalysisContext.

+      analysisServer.sendContextAnalysisCancelledNotifications(
+          context,
+          'Context was removed');
+    }
   }
 
   @override
@@ -572,11 +579,16 @@ class AnalysisServer {
   }
 
   /**
-   * Returns all the [AnalysisErrorInfo] for [file].
-   * It does not wait for all errors to be computed, and returns just the
-   * current state.
+   * Return an analysis error info containing the array of all of the errors and
+   * the line info associated with [file].
+   *
+   * Returns `null` if [file] does not belong to any [AnalysisContext].
    *
-   * May return `null`.
+   * The array of errors will be empty if [file] does not exist or if there are
+   * no errors in [file]. The errors contained in the array can be incomplete.
+   *
+   * This method does not wait for all errors to be computed, and returns just
+   * the current state.
    */
   AnalysisErrorInfo getErrors(String file) {
     // prepare AnalysisContext
@@ -643,12 +655,6 @@ class AnalysisServer {
    *
    * 2. We should complete the future as soon as the file is analyzed (not wait
    *    until the context is completely finished)
-   *
-   * 3. Since contexts can be created and deleted asynchronously as a result of
-   *    changes to the filesystem, there's a danger that the future might never
-   *    get completed. We should add a mechanism to make sure that we return an
-   *    error for any getErrors request that is unsatisfiable due to its context
-   *    being deleted.
    */
   Future onFileAnalysisComplete(String file) {
     // prepare AnalysisContext
@@ -672,13 +678,24 @@ class AnalysisServer {
    * done.
    */
   void sendContextAnalysisDoneNotifications(AnalysisContext context) {
-    Completer completer = contextAnalysisDoneCompleters[context];
+    Completer completer = contextAnalysisDoneCompleters.remove(context);
     if (completer != null) {
       completer.complete();
     }
   }
 
   /**
+   * This method is called when analysis of the given [AnalysisContext] is
+   * cancelled.
+   */
+  void sendContextAnalysisCancelledNotifications(AnalysisContext context, String message) {
+    Completer completer = contextAnalysisDoneCompleters.remove(context);
+    if (completer != null) {
+      completer.completeError(message);
+    }
+  }
+
+  /**
    * Return the [CompilationUnit] of the Dart file with the given [path].
    * Return `null` if the file is not a part of any context.
    */