Add option to ignore ref-updated events emitted by branch deletions

When a branch is deleted, gerrit emits a ref-updated event with a newrev
value of all zeros. This adds a boolean field to optionally not trigger
on these ref-updated events.

Change-Id: Iea75d05ddcb49b0bf748b72b9d2d5472d077f0c6

doc/source/zuul.rst

@@ -422,6 +422,12 @@ explanation of each of the parameters::
     provides.  This field is treated as a regular expression, and
     multiple refs may be listed.
 
+    *ignore-deletes*
+    When a branch is deleted, a ref-updated event is emitted with a newrev
+    of all zeros specified. The ``ignore-deletes`` field is a boolean value
+    that describes whether or not these newrevs trigger ref-updated events.
+    The default is True, which will not trigger ref-updated events.
+
     *approval*
     This is only used for ``comment-added`` events.  It only matches if
     the event has a matching approval associated with it.  Example:

etc/layout.yaml-sample

@@ -30,6 +30,7 @@ pipelines:
       gerrit:
         - event: ref-updated
           ref: ^(?!refs/).*$
+          ignore-deletes: False
 
   - name: gate
     manager: DependentPipelineManager

tests/fixtures/layout-dont-ignore-deletes.yaml

@@ -0,0 +1,16 @@
+includes:
+  - python-file: custom_functions.py
+
+pipelines:
+  - name: post
+    manager: IndependentPipelineManager
+    trigger:
+      gerrit:
+        - event: ref-updated
+          ref: ^(?!refs/).*$
+          ignore-deletes: False
+
+projects:
+  - name: org/project
+    post:
+      - project-post

tests/fixtures/layouts/good_layout.yaml

@@ -20,6 +20,7 @@ pipelines:
       gerrit:
         - event: ref-updated
           ref: ^(?!refs/).*$
+          ignore-deletes: True
 
   - name: gate
     manager: DependentPipelineManager

tests/test_scheduler.py

@@ -891,6 +891,54 @@ class TestScheduler(ZuulTestCase):
         self.assertEqual(len(self.history), 1)
         self.assertIn('project-post', job_names)
 
+    def test_post_ignore_deletes(self):
+        "Test that deleting refs does not trigger post jobs"
+
+        e = {
+            "type": "ref-updated",
+            "submitter": {
+                "name": "User Name",
+            },
+            "refUpdate": {
+                "oldRev": "90f173846e3af9154517b88543ffbd1691f31366",
+                "newRev": "0000000000000000000000000000000000000000",
+                "refName": "master",
+                "project": "org/project",
+            }
+        }
+        self.fake_gerrit.addEvent(e)
+        self.waitUntilSettled()
+
+        job_names = [x.name for x in self.history]
+        self.assertEqual(len(self.history), 0)
+        self.assertNotIn('project-post', job_names)
+
+    def test_post_ignore_deletes_negative(self):
+        "Test that deleting refs does trigger post jobs"
+
+        self.config.set('zuul', 'layout_config',
+                        'tests/fixtures/layout-dont-ignore-deletes.yaml')
+        self.sched.reconfigure(self.config)
+
+        e = {
+            "type": "ref-updated",
+            "submitter": {
+                "name": "User Name",
+            },
+            "refUpdate": {
+                "oldRev": "90f173846e3af9154517b88543ffbd1691f31366",
+                "newRev": "0000000000000000000000000000000000000000",
+                "refName": "master",
+                "project": "org/project",
+            }
+        }
+        self.fake_gerrit.addEvent(e)
+        self.waitUntilSettled()
+
+        job_names = [x.name for x in self.history]
+        self.assertEqual(len(self.history), 1)
+        self.assertIn('project-post', job_names)
+
     def test_build_configuration_branch(self):
         "Test that the right commits are on alternate branches"
 

zuul/layoutvalidator.py

@@ -61,6 +61,7 @@ class LayoutSchema(object):
                       'username': toList(str),
                       'branch': toList(str),
                       'ref': toList(str),
+                      'ignore-deletes': bool,
                       'approval': toList(variable_dict),
                       'require-approval': toList(require_approval),
                       }

zuul/model.py

@@ -22,6 +22,8 @@ OrderedDict = extras.try_imports(['collections.OrderedDict',
                                   'ordereddict.OrderedDict'])
 
 
+EMPTY_GIT_REF = '0' * 40  # git sha of all zeros, used during creates/deletes
+
 MERGER_MERGE = 1          # "git merge"
 MERGER_MERGE_RESOLVE = 2  # "git merge -s resolve"
 MERGER_CHERRY_PICK = 3    # "git cherry-pick"
@@ -1077,7 +1079,8 @@ class BaseFilter(object):
 class EventFilter(BaseFilter):
     def __init__(self, trigger, types=[], branches=[], refs=[],
                  event_approvals={}, comments=[], emails=[], usernames=[],
-                 timespecs=[], required_approvals=[], pipelines=[]):
+                 timespecs=[], required_approvals=[], pipelines=[],
+                 ignore_deletes=True):
         super(EventFilter, self).__init__(
             required_approvals=required_approvals)
         self.trigger = trigger
@@ -1097,6 +1100,7 @@ class EventFilter(BaseFilter):
         self.pipelines = [re.compile(x) for x in pipelines]
         self.event_approvals = event_approvals
         self.timespecs = timespecs
+        self.ignore_deletes = ignore_deletes
 
     def __repr__(self):
         ret = '<EventFilter'
@@ -1109,6 +1113,8 @@ class EventFilter(BaseFilter):
             ret += ' branches: %s' % ', '.join(self._branches)
         if self._refs:
             ret += ' refs: %s' % ', '.join(self._refs)
+        if self.ignore_deletes:
+            ret += ' ignore_deletes: %s' % self.ignore_deletes
         if self.event_approvals:
             ret += ' event_approvals: %s' % ', '.join(
                 ['%s:%s' % a for a in self.event_approvals.items()])
@@ -1160,6 +1166,10 @@ class EventFilter(BaseFilter):
                     matches_ref = True
         if self.refs and not matches_ref:
             return False
+        if self.ignore_deletes and event.newrev == EMPTY_GIT_REF:
+            # If the updated ref has an empty git sha (all 0s),
+            # then the ref is being deleted
+            return False
 
         # comments are ORed
         matches_comment_re = False

zuul/scheduler.py

@@ -347,6 +347,7 @@ class Scheduler(threading.Thread):
                     usernames = toList(trigger.get('username'))
                     if not usernames:
                         usernames = toList(trigger.get('username_filter'))
+                    ignore_deletes = trigger.get('ignore-deletes', True)
                     f = EventFilter(
                         trigger=self.triggers['gerrit'],
                         types=toList(trigger['event']),
@@ -358,7 +359,8 @@ class Scheduler(threading.Thread):
                         usernames=usernames,
                         required_approvals=toList(
                             trigger.get('require-approval')
-                        )
+                        ),
+                        ignore_deletes=ignore_deletes
                     )
                     manager.event_filters.append(f)
             if 'timer' in conf_pipeline['trigger']: