Refactor stages 1, 2 and test_api overhaul.

scripts/slave/recipe_modules/auto_bisect/local_bisect.py

 # Copyright 2015 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 base64
 import collections
 import json
 
+from . import exceptions
 
 def perform_bisect(api, **flags):
   # Try catch all the exceptions thrown in bisection so that recipe can
   # post the failed job result to dashboard
   try:
     bisect_attempts = []
     if api.m.chromium.c.TARGET_PLATFORM != 'android':
       _perform_single_bisect(api, bisect_attempts, **flags)
     else:
       # pick an available device if targe platform is android
       connected_devices = _get_connected_devices(api)
       if not connected_devices:
         raise api.m.step.StepFailure(
             'No Android test devices are available')
       for device in connected_devices:
         api.m.bisect_tester.device_to_test = device
         try:
           _perform_single_bisect(api, bisect_attempts, **flags)
           break
         except api.m.step.StepFailure:
           # Redo the bisect job if target platform is android and bisect
           # failed because the test device disconnected
           current_connected_devices = _get_connected_devices(api)
           if (api.m.bisect_tester.device_to_test not in
               current_connected_devices):
             continue
           else:
             raise
-  except: # pylint: disable=bare-except
+  except exceptions.InconclusiveBisectException:
     if bisect_attempts:
-      bisect_attempts[-1].post_result(halt_on_failure=True)
+      bisect_attempts[-1].post_result()
+    raise api.m.step.StepFailure('Bisect cannot identify a culprit')
+  except Exception: # pylint: disable=bare-except
+    if bisect_attempts:
+      bisect_attempts[-1].post_result()
     raise
 
 def _perform_single_bisect(api, bisect_attempts, **flags):
       bisect_config = dict(api.m.properties.get('bisect_config'))
       if bisect_attempts:
         bisect_config['good_revision'] = bisect_attempts[-1].lkgr.commit_hash
         bisect_config['bad_revision'] = bisect_attempts[-1].fkbr.commit_hash
       bisector = api.create_bisector(bisect_config, **flags)
       bisect_attempts.append(bisector)
       with api.m.step.nest('Gathering reference values'):
-        _gather_reference_range(api, bisector)
+        _gather_reference_range(bisector)
       if (not bisector.failed and bisector.check_improvement_direction() and
           bisector.check_initial_confidence()):
+        bisector.compute_relative_change()
         if bisector.check_reach_adjacent_revision(
             bisector.good_rev): # pragma: no cover
           # Only show this step if bisect has reached adjacent revisions.
           with api.m.step.nest(str('Check bisect finished on revision ' +
                                    bisector.good_rev.revision_string())):
             if bisector.check_bisect_finished(bisector.good_rev):
               bisector.bisect_over = True
         if not bisector.bisect_over:
           _bisect_main_loop(bisector)
       else:
         bisector.bisect_over = True
       bisector.print_result_debug_info()
       bisector.post_result(halt_on_failure=True)
 
 def _get_connected_devices(api):
   api.m.chromium_android.device_status()
   return api.m.chromium_android.devices
 
-def _gather_reference_range(api, bisector):  # pragma: no cover
+def _gather_reference_range(bisector):  # pragma: no cover
   bisector.good_rev.start_job()
   bisector.bad_rev.start_job()
-  bisector.wait_for_all([bisector.good_rev, bisector.bad_rev])
   if bisector.good_rev.failed:
     bisector.surface_result('REF_RANGE_FAIL')
-    api.m.halt('Testing the "good" revision failed')
     bisector.failed = True
+    raise exceptions.InconclusiveBisectException(
+        'Testing the "good" revision failed')
   elif bisector.bad_rev.failed:
     bisector.surface_result('REF_RANGE_FAIL')
-    api.m.halt('Testing the "bad" revision failed')
     bisector.failed = True
-    api.m.halt('Testing the "good" revision failed')
-  else:
-    bisector.compute_relative_change()
-
+    raise exceptions.InconclusiveBisectException(
+        'Testing the "bad" revision failed')
 
 def _bisect_main_loop(bisector):  # pragma: no cover
   """This is the main bisect loop.
 
   It gets an evenly distributed number of revisions in the candidate range,
   then it starts them in parallel and waits for them to finish.
   """
   while not bisector.bisect_over:
     revision_to_check = bisector.get_revision_to_eval()
     if not revision_to_check:
       bisector.bisect_over = True
       break
 
     with bisector.api.m.step.nest(str('Working on revision ' +
                                       revision_to_check.revision_string())):
       bisector.post_result(halt_on_failure=False)
       revision_to_check.start_job()
-      bisector.wait_for(revision_to_check)
 
     if bisector.check_reach_adjacent_revision(revision_to_check):
       # Only show this step if bisect has reached adjacent revisions.
       with bisector.api.m.step.nest(
           str('Check bisect finished on revision ' +
               revision_to_check.revision_string())):
         if bisector.check_bisect_finished(revision_to_check):
             bisector.bisect_over = True