Don't report NO_JOBS to the database

A recent change to report additional buildset results to the db
inadvertently also reported NO_JOBS results.  We should not report
those as they are frequent and uninteresting.  Special case them
and add a test.

Change-Id: Ic7502bd53e2a51d1cc178834344e01cd2a5942db

releasenotes/notes/no-jobs-ec2aa5200d91044b.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    A change in 5.2.3 began reporting NO_JOBS results to the database
+    which was unintentional.  This has been corrected and they are no
+    longer recorded in the database.

tests/fixtures/layouts/no-jobs-reporting.yaml

@@ -0,0 +1,20 @@
+- pipeline:
+    name: check
+    manager: independent
+    trigger:
+      gerrit:
+        - event: patchset-created
+    success:
+      gerrit:
+        Verified: 1
+    failure:
+      gerrit:
+        Verified: -1
+    start:
+      gerrit:
+        Verified: 0
+
+- project:
+    name: org/project
+    check:
+      jobs: []

tests/unit/test_reporting.py

@@ -12,6 +12,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import sqlalchemy as sa
+
 from zuul.model import DequeueEvent
 
 from tests.base import ZuulTestCase, simple_layout
@@ -128,3 +130,29 @@ class TestReporting(ZuulTestCase):
         self.assertIn("Build canceled (check)", A.messages[1])
         self.assertIn("Build started (check)", A.messages[2])
         self.assertIn("Build succeeded (check)", A.messages[3])
+
+    @simple_layout("layouts/no-jobs-reporting.yaml")
+    def test_no_jobs_reporting(self):
+        # Test that we don't report NO_JOBS results
+
+        self.executor_server.hold_jobs_in_build = True
+        A = self.fake_gerrit.addFakeChange("org/project", "master", "A")
+        A.addApproval("Code-Review", 2)
+        self.fake_gerrit.addEvent(A.getPatchsetCreatedEvent(1))
+        self.waitUntilSettled()
+
+        self.assertEqual(0, A.reported)
+        self.assertHistory([])
+
+        tenant = self.scheds.first.sched.abide.tenants.get('tenant-one')
+        pipeline = tenant.layout.pipelines['check']
+        reporter = self.scheds.first.connections.getSqlReporter(
+            pipeline)
+        with self.scheds.first.connections.getSqlConnection().\
+             engine.connect() as conn:
+
+            result = conn.execute(
+                sa.sql.select([reporter.connection.zuul_buildset_table]))
+
+            buildsets = result.fetchall()
+            self.assertEqual(0, len(buildsets))

zuul/manager/__init__.py

@@ -1900,7 +1900,7 @@ class PipelineManager(metaclass=ABCMeta):
                 zuul_driver = self.sched.connections.drivers['zuul']
                 tenant = self.pipeline.tenant
                 zuul_driver.onChangeMerged(tenant, item.change, source)
-        elif action:
+        elif action != 'no-jobs':
             self.sql.reportBuildsetEnd(item.current_build_set,
                                        action, final=True)