Time box _FilesReferencingNameTask.

pkg/analyzer/lib/src/dart/analysis/driver.dart

Index: pkg/analyzer/lib/src/dart/analysis/driver.dart
diff --git a/pkg/analyzer/lib/src/dart/analysis/driver.dart b/pkg/analyzer/lib/src/dart/analysis/driver.dart
index 329f385c52d47eafcf9642f393b06da55b547552..c72732ac2bccb3a0c8fb24fa871d5414aafdb6d3 100644
--- a/pkg/analyzer/lib/src/dart/analysis/driver.dart
+++ b/pkg/analyzer/lib/src/dart/analysis/driver.dart
@@ -1256,30 +1256,33 @@ class _FilesReferencingNameTask {
   _FilesReferencingNameTask(this.driver, this.name);
 
   /**
-   * Perform a single chunk of work, and either complete the [completer] and
+   * Perform work for `10 ms`, and either complete the [completer] and

[Paul Berry, 2016/11/28 20:17:40]

This says "10 ms" but the code below seems to allow 5 ms.  Suggestion: change
the comment to say "a fixed length of time" instead of naming a specific
interval.

[scheglov, 2016/11/28 20:20:17]

Ah, good idea.
Done.

    * return `true` to indicate that the task is done, return `false` to
    * indicate that the task should continue to be run.
    */
   Future<bool> perform() async {
-    // Prepare files to check.
-    if (filesToCheck.isEmpty) {
-      Set<String> newFiles = driver.addedFiles.difference(checkedFiles);
-      filesToCheck.addAll(newFiles);
-    }
+    Stopwatch timer = new Stopwatch()..start();
+    while (timer.elapsedMilliseconds < 5) {

[Brian Wilkerson, 2016/11/28 20:45:04]

Please add a comment describing the tradeoffs you outlined in the CL's comment,
so that we remember the implications of tweaking this value (and explaining why
it was chosen).

[scheglov, 2016/11/28 21:19:27]

Done.

+      // Prepare files to check.
+      if (filesToCheck.isEmpty) {
+        Set<String> newFiles = driver.addedFiles.difference(checkedFiles);
+        filesToCheck.addAll(newFiles);
+      }
 
-    // If no more files to check, complete and done.
-    if (filesToCheck.isEmpty) {
-      completer.complete(referencingFiles);
-      return true;
-    }
+      // If no more files to check, complete and done.
+      if (filesToCheck.isEmpty) {

[Brian Wilkerson, 2016/11/28 20:45:04]

Do we need to perform these two checks on every iteration, or could these be
moved outside the while-loop, allowing us to get more work done in the 5 ms?

[scheglov, 2016/11/28 21:19:27]

These checks are cheap.

+        completer.complete(referencingFiles);
+        return true;
+      }
 
-    // Check the next file.
-    String path = filesToCheck.removeLast();
-    FileState file = driver._fsState.getFileForPath(path);
-    if (file.referencedNames.contains(name)) {
-      referencingFiles.add(path);
+      // Check the next file.
+      String path = filesToCheck.removeLast();
+      FileState file = driver._fsState.getFileForPath(path);
+      if (file.referencedNames.contains(name)) {
+        referencingFiles.add(path);
+      }
+      checkedFiles.add(path);
     }
-    checkedFiles.add(path);
 
     // We're not done yet.
     return false;