presubmit_support: Support getting and adding footers.

Needed by Skia's PostUploadHooks, so that presubmit_support doesn't
depend on git-cl internal classes.

Bug: 1042324
Change-Id: If8f4e6ea035197667cd9705a4274590c4d11511e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2007670
Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

git_footers.py

@@ -130,6 +130,8 @@ def add_footer(message, key, value, after_keys=None, before_keys=None):
   """
   assert key == normalize_name(key), 'Use normalized key'
   new_footer = '%s: %s' % (key, value)
+  if not FOOTER_PATTERN.match(new_footer):
+    raise ValueError('Invalid footer %r' % new_footer)
 
   top_lines, footer_lines, _ = split_footers(message)
   if not footer_lines:

presubmit_support.py

@@ -1127,6 +1127,19 @@ class Change(object):
     self._description_without_tags = (
         '\n'.join(description_without_tags).rstrip())
 
+  def AddDescriptionFooter(self, key, value):
+    """Adds the given footer to the change description.
+
+    Args:
+      key: A string with the key for the git footer. It must conform to
+        the git footers format (i.e. 'List-Of-Tokens') and will be case
+        normalized so that each token is title-cased.
+      value: A string with the value for the git footer.
+    """
+    description = git_footers.add_footer(
+        self.FullDescriptionText(), git_footers.normalize_name(key), value)
+    self.SetDescriptionText(description)
+
   def RepositoryRoot(self):
     """Returns the repository (checkout) root directory for this change,
     as an absolute path.
@@ -1139,11 +1152,20 @@ class Change(object):
       raise AttributeError(self, attr)
     return self.tags.get(attr)
 
+  def GitFootersFromDescription(self):
+    """Return the git footers present in the description.
+
+    Returns:
+      footers: A dict of {footer: [values]} containing a multimap of the footers
+        in the change description.
+    """
+    return git_footers.parse_footers(self.FullDescriptionText())
+
   def BugsFromDescription(self):
     """Returns all bugs referenced in the commit description."""
     tags = [b.strip() for b in self.tags.get('BUG', '').split(',') if b.strip()]
     footers = []
-    parsed = git_footers.parse_footers(self._full_description)
+    parsed = self.GitFootersFromDescription()
     unsplit_footers = parsed.get('Bug', []) + parsed.get('Fixed', [])
     for unsplit_footer in unsplit_footers:
       footers += [b.strip() for b in unsplit_footer.split(',')]
@@ -1160,7 +1182,7 @@ class Change(object):
     tags = [r.strip() for r in self.tags.get('TBR', '').split(',') if r.strip()]
     # TODO(agable): Remove support for 'Tbr:' when TBRs are programmatically
     # determined by self-CR+1s.
-    footers = git_footers.parse_footers(self._full_description).get('Tbr', [])
+    footers = self.GitFootersFromDescription().get('Tbr', [])
     return sorted(set(tags + footers))
 
   # TODO(agable): Delete these once we're sure they're unused.

tests/git_footers_test.py

@@ -178,6 +178,9 @@ My commit message is my best friend. It is my life. I must master it.
         'Header.\n\nBug: v8\nChange-Id: Ix\nN=t\nT=z')
 
   def testAddFooter(self):
+    with self.assertRaises(ValueError):
+      git_footers.add_footer('', 'Invalid Footer', 'Value')
+
     self.assertEqual(
         git_footers.add_footer('', 'Key', 'Value'),
         '\nKey: Value')

tests/presubmit_unittest.py

@@ -1391,6 +1391,41 @@ class ChangeUnittest(PresubmitTestsBase):
     self.assertEqual('WHIZ=bang\nbar\nFOO=baz', change.FullDescriptionText())
     self.assertEqual({'WHIZ': 'bang', 'FOO': 'baz'}, change.tags)
 
+  def testAddDescriptionFooter(self):
+    change = presubmit.Change(
+        '', 'foo\nDRU=ro\n\nChange-Id: asdf', self.fake_root_dir, [], 3, 5, '')
+    change.AddDescriptionFooter('my-footer', 'my-value')
+    self.assertEqual(
+        'foo\nDRU=ro\n\nChange-Id: asdf\nMy-Footer: my-value',
+        change.FullDescriptionText())
+
+  def testAddDescriptionFooter_NoPreviousFooters(self):
+    change = presubmit.Change(
+        '', 'foo\nDRU=ro', self.fake_root_dir, [], 3, 5, '')
+    change.AddDescriptionFooter('my-footer', 'my-value')
+    self.assertEqual(
+        'foo\nDRU=ro\n\nMy-Footer: my-value', change.FullDescriptionText())
+
+  def testAddDescriptionFooter_InvalidFooter(self):
+    change = presubmit.Change(
+        '', 'foo\nDRU=ro', self.fake_root_dir, [], 3, 5, '')
+    with self.assertRaises(ValueError):
+      change.AddDescriptionFooter('invalid.characters in:the', 'footer key')
+
+  def testGitFootersFromDescription(self):
+    change = presubmit.Change(
+        '', 'foo\n\nChange-Id: asdf\nBug: 1\nBug: 2\nNo-Try: True',
+        self.fake_root_dir, [], 0, 0, '')
+    self.assertEqual({
+          'Change-Id': ['asdf'],
+          'Bug': ['2', '1'],
+          'No-Try': ['True'],
+      }, change.GitFootersFromDescription())
+
+  def testGitFootersFromDescription_NoFooters(self):
+    change = presubmit.Change('', 'foo', self.fake_root_dir, [], 0, 0, '')
+    self.assertEqual({}, change.GitFootersFromDescription())
+
   def testBugFromDescription_FixedAndBugGetDeduped(self):
     change = presubmit.Change(
         '', 'foo\n\nChange-Id: asdf\nBug: 1, 2\nFixed:2, 1 ',