_scheduler/queue.py: Queue.done() return value now represents whether it was "skipped"

This is entirely for reporting purposes, so that operations which needed
to be processed in order to determine if they were possible or not (like
pulling an artifact which we dont know exists remotely yet), can display
themselves as "skipped" in the case that nothing was done.

1 files changed, 21 insertions, 9 deletions

diff --git a/buildstream/_scheduler/queue.py b/buildstream/_scheduler/queue.py
index ce0a1e682..6f82d3266 100644
--- a/buildstream/_scheduler/queue.py
+++ b/buildstream/_scheduler/queue.py
@@ -125,6 +125,11 @@ class Queue():
     #    result (any): The return value of the process() implementation
     #    returncode (int): The process return code, 0 = success
     #
+    # Returns:
+    #    (bool): True if the element should appear to be skipped,
+    #            this is useful in cases where we can only determine
+    #            "skipped" status after processing.
+    #
     def done(self, element, result, returncode):
         pass
 
@@ -182,19 +187,26 @@ class Queue():
 
     def job_done(self, job, returncode, element):
 
-        if returncode == 0:
-            self.done_queue.append(element)
-            self.processed_elements.append(element)
-        else:
-            self.failed_elements.append(element)
-
         # Shutdown the job
         job.shutdown()
-
         self.active_jobs.remove(job)
 
-        # Give the result of the job to the Queue implementor
-        self.done(element, job.result, returncode)
+        # Give the result of the job to the Queue implementor,
+        # and determine if it should be considered as processed
+        # or skipped.
+        if self.done(element, job.result, returncode):
+            skip = True
+        else:
+            skip = False
+
+        if returncode == 0:
+            self.done_queue.append(element)
+            if skip:
+                self.skipped_elements.append(element)
+            else:
+                self.processed_elements.append(element)
+        else:
+            self.failed_elements.append(element)
 
         # Notify frontend
         self.scheduler.job_completed(job, returncode == 0)