[pinpoint] Add message in bug when there are no change points.

dashboard/dashboard/pinpoint/models/job.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import collections
 import logging
 import os
 import traceback
 
 from google.appengine.api import taskqueue
@@ skipping 96 matching lines @@
     return 'https://%s/job/%s' % (os.environ['HTTP_HOST'], self.job_id)
 
   def AddChange(self, change):
     self.state.AddChange(change)
 
   def Start(self):
     self.Schedule()
     self._PostBugComment('started')
 
   def Complete(self):
-    self._PostBugComment('completed')
+    self._PostBugComment('completed', include_differences=True)
 
   def Fail(self):
     self.exception = traceback.format_exc()
-    self._PostBugComment('stopped with an error')
+    self._PostBugComment('stopped with an error', include_differences=True)
 
   def Schedule(self):
     task = taskqueue.add(queue_name='job-queue', url='/api/run/' + self.job_id,
                          countdown=_TASK_INTERVAL)
     self.task = task.name
 
   def Run(self):
     self.exception = None  # In case the Job succeeds on retry.
     self.task = None  # In case an exception is thrown.
 
@@ skipping 21 matching lines @@
 
         'created': self.created.isoformat(),
         'updated': self.updated.isoformat(),
         'exception': self.exception,
         'status': self.status,
     }
     if include_state:
       d.update(self.state.AsDict())
     return d
 
-  def _PostBugComment(self, status):
+  def _PostBugComment(self, status, include_differences=False):
     if not self.bug_id:
       return
 
     title = '%s Pinpoint job %s.' % (_ROUND_PUSHPIN, status)
     header = '\n'.join((title, self.url))
 
-    # Include list of Changes.
     change_details = []
-    for _, change in self.state.Differences():
-      # TODO: Store the commit info in the Commit.
-      commit = change.last_commit
-      commit_info = gitiles_service.CommitInfo(commit.repository_url,
-                                               commit.git_hash)
-      subject = '<b>%s</b>' % commit_info['message'].split('\n', 1)[0]
-      author = commit_info['author']['email']
-      time = commit_info['committer']['time']
-
-      byline = 'By %s %s %s' % (author, _MIDDLE_DOT, time)
-      git_link = commit.repository + '@' + commit.git_hash
-      change_details.append('\n'.join((subject, byline, git_link)))
+    if include_differences:
+      # Include list of Changes.
+      differences = tuple(self.state.Differences())
+      if differences:
+        if len(differences) == 1:
+          change_details.append(
+              '<b>Found significant differences after 1 commit:</b>')
+        else:
+          change_details.append(
+              '<b>Found significant differences after each of %d commits:</b>' %
+              len(differences))
+        for _, change in differences:
+          change_details.append(_FormatChangeForBug(change))
+      else:
+        change_details.append("<b>Couldn't reproduce a difference.</b>")
 
     comment = '\n\n'.join([header] + change_details)
 
     issue_tracker = issue_tracker_service.IssueTrackerService(
         utils.ServiceAccountHttp())
     issue_tracker.AddBugComment(self.bug_id, comment, send_email=False)
 
 
 class _JobState(object):
   """The internal state of a Job.
@@ skipping 151 matching lines @@
     # Here, "the same" means that we fail to reject the null hypothesis. We can
     # never be completely sure that the two Changes have the same results, but
     # we've run everything that we planned to, and didn't detect any difference.
     if (len(attempts_a) >= self._repeat_count and
         len(attempts_b) >= self._repeat_count):
       return _SAME
 
     return _UNKNOWN
 
 
+def _FormatChangeForBug(change):
+  # TODO: Store the commit info in the Commit.
+  commit = change.last_commit
+  commit_info = gitiles_service.CommitInfo(commit.repository_url,
+                                           commit.git_hash)
+  subject = '<b>%s</b>' % commit_info['message'].split('\n', 1)[0]
+  author = commit_info['author']['email']
+  time = commit_info['committer']['time']
+
+  byline = 'By %s %s %s' % (author, _MIDDLE_DOT, time)
+  git_link = commit.repository + '@' + commit.git_hash
+  return '\n'.join((subject, byline, git_link))
+
+
 def _CombineResultsPerQuest(attempts):
   aggregate_results = collections.defaultdict(list)
   for attempt in attempts:
     if not attempt.completed:
       continue
 
     for quest, results in attempt.result_values.iteritems():
       aggregate_results[quest] += results
 
   return aggregate_results
 
 
 def _CompareValues(values_a, values_b):
   if not (values_a and values_b):
     return _UNKNOWN
 
   try:
     p_value = mann_whitney_u.MannWhitneyU(values_a, values_b)
   except ValueError:
     return _UNKNOWN
 
   if p_value < _SIGNIFICANCE_LEVEL:
     return _DIFFERENT
   else:
     return _UNKNOWN