Check if json exists in ensure_checkout's finally block

The step_result json can currently be empty if the orchestrator build
is canceled while running bot_update. Trying to do
step_result.json.output in the finally block raises an "Uncaught
exception AttributeError".
Ex: https://ci.chromium.org/ui/p/chromium/builders/try/win10_chromium_x64_rel_ng/1121568/overview

This change checks for the json attr before trying to read json.output.

Bug: 1305332
Change-Id: I1dc277642ece1b96144be6381a7c4b8426cb2bc6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3518372Reviewed-by: Garrett Beaty <gbeaty@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Stephanie Kim <kimstephanie@google.com>

recipes/README.recipes.md

@@ -59,7 +59,7 @@ Recipe module to ensure a checkout is consistent on a bot.
 
 Wrapper for easy calling of bot_update.
 
-— **def [deapply\_patch](/recipes/recipe_modules/bot_update/api.py#516)(self, bot_update_step):**
+— **def [deapply\_patch](/recipes/recipe_modules/bot_update/api.py#522)(self, bot_update_step):**
 
 Deapplies a patch, taking care of DEPS and solution revisions properly.
     
@@ -93,7 +93,7 @@ Args:
     bot_update module ONLY supports one change. Users may specify a change
     via tryserver.set_change() and explicitly set this flag False.
 
-— **def [get\_project\_revision\_properties](/recipes/recipe_modules/bot_update/api.py#493)(self, project_name, gclient_config=None):**
+— **def [get\_project\_revision\_properties](/recipes/recipe_modules/bot_update/api.py#499)(self, project_name, gclient_config=None):**
 
 Returns all property names used for storing the checked-out revision of
 a given project.
@@ -109,7 +109,7 @@ Returns (list of str): All properties that'll hold the checked-out revision
 
 &emsp; **@property**<br>&mdash; **def [last\_returned\_properties](/recipes/recipe_modules/bot_update/api.py#49)(self):**
 
-&mdash; **def [resolve\_fixed\_revision](/recipes/recipe_modules/bot_update/api.py#444)(self, bot_update_json, name):**
+&mdash; **def [resolve\_fixed\_revision](/recipes/recipe_modules/bot_update/api.py#450)(self, bot_update_json, name):**
 
 Sets a fixed revision for a single dependency using project revision
 properties.
@@ -988,11 +988,11 @@ Raises:
 
 ### *recipes* / [bot\_update:examples/full](/recipes/recipe_modules/bot_update/examples/full.py)
 
-[DEPS](/recipes/recipe_modules/bot_update/examples/full.py#7): [bot\_update](#recipe_modules-bot_update), [gclient](#recipe_modules-gclient), [gerrit](#recipe_modules-gerrit), [tryserver](#recipe_modules-tryserver), [recipe\_engine/buildbucket][recipe_engine/recipe_modules/buildbucket], [recipe\_engine/json][recipe_engine/recipe_modules/json], [recipe\_engine/path][recipe_engine/recipe_modules/path], [recipe\_engine/platform][recipe_engine/recipe_modules/platform], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/runtime][recipe_engine/recipe_modules/runtime]
+[DEPS](/recipes/recipe_modules/bot_update/examples/full.py#9): [bot\_update](#recipe_modules-bot_update), [gclient](#recipe_modules-gclient), [gerrit](#recipe_modules-gerrit), [tryserver](#recipe_modules-tryserver), [recipe\_engine/buildbucket][recipe_engine/recipe_modules/buildbucket], [recipe\_engine/json][recipe_engine/recipe_modules/json], [recipe\_engine/path][recipe_engine/recipe_modules/path], [recipe\_engine/platform][recipe_engine/recipe_modules/platform], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/runtime][recipe_engine/recipe_modules/runtime]
 
 PYTHON_VERSION_COMPATIBILITY: PY2+3
 
-&mdash; **def [RunSteps](/recipes/recipe_modules/bot_update/examples/full.py#25)(api):**
+&mdash; **def [RunSteps](/recipes/recipe_modules/bot_update/examples/full.py#27)(api):**
 ### *recipes* / [bot\_update:tests/do\_not\_retry\_patch\_failures\_in\_cq](/recipes/recipe_modules/bot_update/tests/do_not_retry_patch_failures_in_cq.py)
 
 [DEPS](/recipes/recipe_modules/bot_update/tests/do_not_retry_patch_failures_in_cq.py#9): [bot\_update](#recipe_modules-bot_update), [gclient](#recipe_modules-gclient), [recipe\_engine/buildbucket][recipe_engine/recipe_modules/buildbucket], [recipe\_engine/cq][recipe_engine/recipe_modules/cq], [recipe\_engine/properties][recipe_engine/recipe_modules/properties], [recipe\_engine/step][recipe_engine/recipe_modules/step]

recipes/recipe_modules/bot_update/api.py

@@ -306,7 +306,13 @@ class BotUpdateApi(recipe_api.RecipeApi):
       step_result = f.result
       raise
     finally:
-      if step_result and step_result.json.output:
+      # The step_result can be missing the json attribute if the build
+      # is shutting down and the bot_update script is not able to finish
+      # writing the json output.
+      # An AttributeError occuring in this finally block swallows any
+      # StepFailure that may bubble up.
+      if (step_result and hasattr(step_result, 'json')
+          and step_result.json.output):
         result = step_result.json.output
         self._last_returned_properties = result.get('properties', {})
 

recipes/recipe_modules/bot_update/examples/full.py

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+from recipe_engine import post_process
+
 PYTHON_VERSION_COMPATIBILITY = 'PY2+3'
 
 DEPS = [
@@ -180,6 +182,11 @@ def GenTests(api):
       api.properties(fail_patch='download') +
       api.step_data('bot_update', retcode=87)
   )
+  yield (api.test('tryjob_fail_missing_bot_update_json') + try_build() +
+         api.override_step_data('bot_update', retcode=1) +
+         api.post_process(post_process.ResultReasonRE, 'Infra Failure.*') +
+         api.post_process(post_process.StatusException) +
+         api.post_process(post_process.DropExpectation))
   yield (
       api.test('clobber') +
       api.properties(clobber=1)