Fix handling of missing Gold links

Fixes the Gold interaction code not properly handling the case where a
bug on Gold's end prevents it from writing a triage link to the provided
file.

Bug: 1124368
Change-Id: Ic3e9a4d8808b97831fba1c4f42338b6b1435acde
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391505
Commit-Queue: Brian Sheedy <bsheedy@chromium.org>
Commit-Queue: Sven Zheng <svenzheng@chromium.org>
Auto-Submit: Brian Sheedy <bsheedy@chromium.org>
Reviewed-by: Sven Zheng <svenzheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804107}

build/skia_gold_common/skia_gold_session.py

@@ -282,9 +282,16 @@ class SkiaGoldSession(object):
       try:
         with open(self._triage_link_file) as tlf:
           triage_link = tlf.read().strip()
-        self._comparison_results[name].internal_triage_link = triage_link
-        self._comparison_results[name].public_triage_link =\
-            self._GeneratePublicTriageLink(triage_link)
+        if not triage_link:
+          self._comparison_results[name].triage_link_omission_reason = (
+              'Gold did not provide a triage link. This is likely a bug on '
+              "Gold's end.")
+          self._comparison_results[name].internal_triage_link = None
+          self._comparison_results[name].public_triage_link = None
+        else:
+          self._comparison_results[name].internal_triage_link = triage_link
+          self._comparison_results[name].public_triage_link =\
+              self._GeneratePublicTriageLink(triage_link)
       except IOError:
         self._comparison_results[name].triage_link_omission_reason = (
             'Failed to read triage link from file')

build/skia_gold_common/skia_gold_session_unittest.py

@@ -622,6 +622,27 @@ class SkiaGoldSessionCompareTest(fake_filesystem_unittest.TestCase):
     self.assertEqual(session.GetTriageLinks('name'),
                      (public_link, internal_link))
 
+  @mock.patch.object(skia_gold_session.SkiaGoldSession, '_RunCmdForRcAndOutput')
+  def test_validOmissionOnMissingLink(self, cmd_mock):
+    args = createSkiaGoldArgs(git_revision='a')
+    sgp = skia_gold_properties.SkiaGoldProperties(args)
+    session = skia_gold_session.SkiaGoldSession(self._working_dir, sgp,
+                                                'keys_file', None, None)
+
+    def WriteTriageLinkFile(_):
+      with open(session._triage_link_file, 'w'):
+        pass
+      return (1, None)
+
+    cmd_mock.side_effect = WriteTriageLinkFile
+    rc, _ = session.Compare('name', 'png_file')
+    self.assertEqual(rc, 1)
+    comparison_result = session._comparison_results['name']
+    self.assertEqual(comparison_result.public_triage_link, None)
+    self.assertEqual(comparison_result.internal_triage_link, None)
+    self.assertIn('Gold did not provide a triage link',
+                  comparison_result.triage_link_omission_reason)
+
   @mock.patch.object(skia_gold_session.SkiaGoldSession, '_RunCmdForRcAndOutput')
   def test_validOmissionOnIoError(self, cmd_mock):
     cmd_mock.return_value = (1, None)