Print a suggested commit description after removing flaky lines.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/update_test_expectations.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Updates TestExpectations based on results in builder bots.
 
 Scans the TestExpectations file and uses results from actual builder bots runs
 to remove tests that are marked as flaky but don't fail in the specified way.
 
 E.g. If a test has this expectation:
     bug(test) fast/test.html [ Failure Pass ]
 
 And all the runs on builders have passed the line will be removed.
 
 Additionally, the runs don't all have to be Passing to remove the line;
 as long as the non-Passing results are of a type not specified in the
 expectation this line will be removed. For example, if this is the
 expectation:
 
     bug(test) fast/test.html [ Crash Pass ]
 
 But the results on the builders show only Passes and Timeouts, the line
 will be removed since there's no Crash results.
 """
 
 import argparse
 import logging
 import webbrowser
 
+from webkitpy.layout_tests.models.test_expectations import CHROMIUM_BUG_PREFIX
 from webkitpy.layout_tests.models.test_expectations import TestExpectations
 from webkitpy.tool.commands.flaky_tests import FlakyTests
 
 _log = logging.getLogger(__name__)
 
 
 def main(host, bot_test_expectations_factory, argv):
     parser = argparse.ArgumentParser(epilog=__doc__, formatter_class=argparse.RawTextHelpFormatter)
     parser.add_argument('--verbose', '-v', action='store_true', default=False, help='enable more verbose logging')
     parser.add_argument('--show-results',
                         '-s',
                         action='store_true',
                         default=False,
                         help='Open results dashboard for all removed lines')
     args = parser.parse_args(argv)
 
     logging.basicConfig(level=logging.DEBUG if args.verbose else logging.INFO, format='%(levelname)s: %(message)s')
 
     port = host.port_factory.get()
     expectations_file = port.path_to_generic_test_expectations_file()
     if not host.filesystem.isfile(expectations_file):
         _log.warning("Didn't find generic expectations file at: " + expectations_file)
         return 1
 
-    remove_flakes_o_matic = RemoveFlakesOMatic(host,
-                                               port,
-                                               bot_test_expectations_factory,
-                                               webbrowser)
+    remove_flakes_o_matic = RemoveFlakesOMatic(
+        host, port, bot_test_expectations_factory, webbrowser)
 
     test_expectations = remove_flakes_o_matic.get_updated_test_expectations()
 
     if args.show_results:
         remove_flakes_o_matic.show_removed_results()
 
-    remove_flakes_o_matic.write_test_expectations(test_expectations,
-                                                  expectations_file)
+    remove_flakes_o_matic.write_test_expectations(test_expectations, expectations_file)
+    remove_flakes_o_matic.print_suggested_commit_description()
     return 0
 
 
 class RemoveFlakesOMatic(object):
 
     def __init__(self, host, port, bot_test_expectations_factory, browser):
         self._host = host
         self._port = port
         self._expectations_factory = bot_test_expectations_factory
         self._builder_results_by_path = {}
@@ skipping 236 matching lines @@
             test_expectations.remove(expectation)
 
             # Remove associated comments and whitespace if we've removed the last expectation under
             # a comment block. Only remove a comment block if it's not separated from the test
             # expectation line by whitespace.
             self._remove_associated_comments_and_whitespace(test_expectations, index)
 
         return test_expectations
 
     def show_removed_results(self):
-        """Opens removed lines in the results dashboard.
+        """Opens a browser showing the removed lines in the results dashboard.
 
-        Opens the results dashboard in the browser, showing all the tests for lines that the script
-        removed from the TestExpectations file and allowing the user to manually confirm the
-        results.
+        Opens the results dashboard in the browser, showing all the tests for
+        lines removed from the TestExpectations file, allowing the user to
+        manually confirm the results.
         """
-        removed_test_names = ','.join(x.name for x in self._expectations_to_remove())
-        url = FlakyTests.FLAKINESS_DASHBOARD_URL % removed_test_names
-
+        url = self._flakiness_dashboard_url()
         _log.info('Opening results dashboard: ' + url)
         self._browser.open(url)
 
     def write_test_expectations(self, test_expectations, test_expectations_file):
         """Writes the given TestExpectations object to the filesystem.
 
         Args:
             test_expectations: The TestExpectations object to write.
             test_expectations_file: The full file path of the Blink
                 TestExpectations file. This file will be overwritten.
         """
         self._host.filesystem.write_text_file(
             test_expectations_file,
             TestExpectations.list_to_string(test_expectations, reconstitute_only_these=[]))
+
+    def print_suggested_commit_description(self):
+        """Prints the body of a suggested CL description after removing some lines."""
+        dashboard_url = self._flakiness_dashboard_url()
+        bugs = ','.join(self._bug_numbers())
+        message = ('Remove flaky TestExpectations for tests which appear non-flaky recently.\n\n'
+                   'This change was made by the update-test-expectations script.\n\n'
+                   'Recent test results history:\n%s\n\n'
+                   'BUG=%s') % (dashboard_url, bugs)
+        _log.info('Suggested commit description:\n' + message)
+
+    def _flakiness_dashboard_url(self):
+        removed_test_names = ','.join(x.name for x in self._expectations_to_remove())
+        return FlakyTests.FLAKINESS_DASHBOARD_URL % removed_test_names
+
+    def _bug_numbers(self):
+        """Returns the list of all bug numbers affected by this change."""
+        numbers = []
+        for line in self._expectations_to_remove():
+            for bug in line.bugs:
+                if bug.startswith(CHROMIUM_BUG_PREFIX):
+                    numbers.append(bug[len(CHROMIUM_BUG_PREFIX):])
+        return sorted(numbers)