[run_web_tests] Fix --reset-results when platform baseline exists but fallback doesn't

Previously, --reset-results removed the existing platform baseline
without recreating one if the fallback baseline doesn't exist.

Fix the issue by checking non-exist and non-missing condition
before removing the current baseline.

Bug: 845781
Change-Id: I7dbe46665d9574b310020c4ffc4041b6235d5570
Reviewed-on: https://chromium-review.googlesource.com/1173483
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583005}

third_party/blink/tools/blinkpy/web_tests/controllers/single_test_runner.py

@@ -189,9 +189,16 @@ class SingleTestRunner(object):
     def _save_baseline_data(self, data, extension, is_missing):
         if data is None:
             return
+
         port = self._port
         fs = self._filesystem
 
+        # It's OK that a testharness test or image-first test doesn't have the
+        # particular baseline, as long as |is_missing| is False.
+        current_expected_path = port.expected_filename(self._test_name, extension)
+        if not fs.exists(current_expected_path) and not is_missing:
+            return
+
         flag_specific_dir = port.baseline_flag_specific_dir()
         if flag_specific_dir:
             output_dir = fs.join(flag_specific_dir, fs.dirname(self._test_name))
@@ -212,11 +219,9 @@ class SingleTestRunner(object):
             _log.info('Removing the current baseline "%s"', port.relative_test_filename(output_path))
             fs.remove(output_path)
 
+        # Note that current_expected_path may change because of the above file removal.
         current_expected_path = port.expected_filename(self._test_name, extension)
-        if not fs.exists(current_expected_path):
-            if not is_missing or not self._options.reset_results:
-                return
-        elif fs.sha1(current_expected_path) == hashlib.sha1(data).hexdigest():
+        if fs.exists(current_expected_path) and fs.sha1(current_expected_path) == hashlib.sha1(data).hexdigest():
             if self._options.reset_results:
                 _log.info('Not writing new expected result "%s" because it is the same as the current expected result',
                           port.relative_test_filename(output_path))

third_party/blink/tools/blinkpy/web_tests/run_webkit_tests_unittest.py

@@ -1510,6 +1510,58 @@ class RebaselineTest(unittest.TestCase, StreamTestingMixin):
             'virtual/virtual_failures/failures/unexpected/text-image-checksum',
             expected_extensions=['.png'])
 
+    def test_new_platform_baseline_with_fallback(self):
+        # Test that we update the existing baseline in the platform-specific
+        # directory if the new baseline is different, with existing fallback
+        # baseline (which should not matter).
+        host = MockHost()
+        host.filesystem.write_text_file(
+            test.LAYOUT_TEST_DIR +
+            '/platform/test-mac-mac10.10/failures/unexpected/text-image-checksum-expected.png',
+            'wrong-png-baseline')
+
+        details, log_stream, _ = logging_run(
+            [
+                '--reset-results',
+                'failures/unexpected/text-image-checksum.html'
+            ],
+            tests_included=True, host=host)
+        file_list = host.filesystem.written_files.keys()
+        self.assertEqual(details.exit_code, 0)
+        self.assertEqual(len(file_list), 7)
+        # We should reset the platform image baseline.
+        self.assert_baselines(
+            file_list, log_stream,
+            'platform/test-mac-mac10.10/failures/unexpected/text-image-checksum',
+            expected_extensions=['.png'])
+
+    def test_new_platform_baseline_without_fallback(self):
+        # Test that we update the existing baseline in the platform-specific
+        # directory if the new baseline is different, without existing fallback
+        # baseline (which should not matter).
+        host = MockHost()
+        host.filesystem.write_text_file(
+            test.LAYOUT_TEST_DIR +
+            '/platform/test-mac-mac10.10/failures/unexpected/text-image-checksum-expected.png',
+            'wrong-png-baseline')
+        host.filesystem.remove(
+            test.LAYOUT_TEST_DIR + '/failures/unexpected/text-image-checksum-expected.png')
+
+        details, log_stream, _ = logging_run(
+            [
+                '--reset-results',
+                'failures/unexpected/text-image-checksum.html'
+            ],
+            tests_included=True, host=host)
+        file_list = host.filesystem.written_files.keys()
+        self.assertEqual(details.exit_code, 0)
+        self.assertEqual(len(file_list), 8)
+        # We should reset the platform image baseline.
+        self.assert_baselines(
+            file_list, log_stream,
+            'platform/test-mac-mac10.10/failures/unexpected/text-image-checksum',
+            expected_extensions=['.png'])
+
     def test_new_virtual_baseline_optimize(self):
         # Test removing existing baselines under flag-specific directory if the
         # actual results are the same as the fallback baselines.