Presubmit: if there are warnings and may_prompt is false, don't fail.

Rationale: The description of the -f flag to git cl upload is "force
yes to questions (don't prompt)", so when git cl upload -f is run,
I would expect it to abort on errors, but still continue on warnings.

When the -f is given, DoPresubmitChecks is called with may_prompt=False;
this CL would change the behavior of DoPresubmitChecks so that when
may_prompt is False and there are warnings but no errors, then that
means we will print warnings but not fail.

BUG=671683

Change-Id: Ie0f1ac1983d875226db8ad741cbce3dc0bc4eb96
Reviewed-on: https://chromium-review.googlesource.com/419148
Reviewed-by: Aaron Gable <agable@chromium.org>
Commit-Queue: Quinten Yearsley <qyearsley@chromium.org>

presubmit_support.py

@@ -1174,7 +1174,6 @@ class PresubmitExecuter(object):
     os.chdir(main_path)
     return result
 
-
 def DoPresubmitChecks(change,
                       committing,
                       verbose,
@@ -1201,7 +1200,8 @@ def DoPresubmitChecks(change,
     output_stream: A stream to write output from presubmit tests to.
     input_stream: A stream to read input from the user.
     default_presubmit: A default presubmit script to execute in any case.
-    may_prompt: Enable (y/n) questions on warning or error.
+    may_prompt: Enable (y/n) questions on warning or error. If False,
+                any questions are answered with yes by default.
     rietveld_obj: rietveld.Rietveld object.
     gerrit_obj: provides basic Gerrit codereview functionality.
     dry_run: if true, some Checks will be skipped.
@@ -1271,14 +1271,14 @@ def DoPresubmitChecks(change,
     if total_time > 1.0:
       output.write("Presubmit checks took %.1fs to calculate.\n\n" % total_time)
 
-    if not errors:
-      if not warnings:
-        output.write('Presubmit checks passed.\n')
-      elif may_prompt:
-        output.prompt_yes_no('There were presubmit warnings. '
-                            'Are you sure you wish to continue? (y/N): ')
-      else:
-        output.fail()
+    if errors:
+      output.fail()
+    elif warnings:
+      output.write('There were presubmit warnings. ')
+      if may_prompt:
+        output.prompt_yes_no('Are you sure you wish to continue? (y/N): ')
+    else:
+      output.write('Presubmit checks passed.\n')
 
     global _ASKED_FOR_FEEDBACK
     # Ask for feedback one time out of 5.

tests/presubmit_unittest.py

@@ -634,6 +634,38 @@ class PresubmitUnittest(PresubmitTestsBase):
     self.assertEqual(output.getvalue().count(
         'Running presubmit upload checks ...\n'), 1)
 
+  def testDoPresubmitChecksWithWarningsAndNoPrompt(self):
+    presubmit_path = presubmit.os.path.join(self.fake_root_dir, 'PRESUBMIT.py')
+    haspresubmit_path = presubmit.os.path.join(
+        self.fake_root_dir, 'haspresubmit', 'PRESUBMIT.py')
+    inherit_path = presubmit.os.path.join(self.fake_root_dir,
+                                          self._INHERIT_SETTINGS)
+    presubmit.os.path.isfile(inherit_path).AndReturn(False)
+    presubmit.os.listdir(self.fake_root_dir).AndReturn(['PRESUBMIT.py'])
+    presubmit.os.path.isfile(presubmit_path).AndReturn(True)
+    presubmit.os.listdir(presubmit.os.path.join(
+        self.fake_root_dir, 'haspresubmit')).AndReturn(['PRESUBMIT.py'])
+    presubmit.os.path.isfile(haspresubmit_path).AndReturn(True)
+    presubmit.gclient_utils.FileRead(presubmit_path, 'rU').AndReturn(
+        self.presubmit_text)
+    presubmit.gclient_utils.FileRead(haspresubmit_path, 'rU').AndReturn(
+        self.presubmit_text)
+    presubmit.random.randint(0, 4).AndReturn(1)
+    self.mox.ReplayAll()
+
+    change = self.ExampleChange(extra_lines=['NOSUCHKEY=http://tracker/123'])
+
+    # There is no input buffer and may_prompt is set to False.
+    output = presubmit.DoPresubmitChecks(
+        change=change, committing=False, verbose=True,
+        output_stream=None, input_stream=None,
+        default_presubmit=None, may_prompt=False, rietveld_obj=None)
+    # A warning is printed, and should_continue is True.
+    self.failUnless(output.should_continue())
+    self.assertEquals(output.getvalue().count('??'), 2)
+    self.assertEqual(output.getvalue().count(
+        'Running presubmit upload checks ...\n'), 1)
+
   def testDoPresubmitChecksNoWarningPromptIfErrors(self):
     presubmit_path = presubmit.os.path.join(self.fake_root_dir, 'PRESUBMIT.py')
     haspresubmit_path = presubmit.os.path.join(