Make git_footers.add_footer more flexible

This allows inserted footers to be specified as either before
or after other potentially-present footers.

It has one slight behavior change (reflected in the tests):
If after_keys is specified but *doesn't match* any pre-existing
footers, then the behavior does *not* switch to "insert as early
as possible". The behavior switch only happens if the after_keys
actually match a footer.

R=iannucci@chromium.org

Bug: 710547
Change-Id: If557978fe9309785285056eb557acbdc87960bb2
Reviewed-on: https://chromium-review.googlesource.com/487606
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>

git_footers.py

@@ -84,13 +84,16 @@ def add_footer_change_id(message, change_id):
                     after_keys=['Bug', 'Issue', 'Test', 'Feature'])
 
 
-def add_footer(message, key, value, after_keys=None):
+def add_footer(message, key, value, after_keys=None, before_keys=None):
   """Returns a message with given footer appended.
 
-  If after_keys is None (default), appends footer last.
-  Otherwise, after_keys must be iterable of footer keys, then the new footer
-  would be inserted at the topmost position such there would be no footer lines
-  after it with key matching one of after_keys.
+  If after_keys and before_keys are both None (default), appends footer last.
+  If after_keys is provided and matches footers already present, inserts footer
+  as *early* as possible while still appearing after all provided keys, even
+  if doing so conflicts with before_keys.
+  If before_keys is provided, inserts footer as late as possible while still
+  appearing before all provided keys.
+
   For example, given
       message='Header.\n\nAdded: 2016\nBug: 123\nVerified-By: CQ'
       after_keys=['Bug', 'Issue']
@@ -99,22 +102,28 @@ def add_footer(message, key, value, after_keys=None):
   assert key == normalize_name(key), 'Use normalized key'
   new_footer = '%s: %s' % (key, value)
 
-  top_lines, footer_lines, parsed_footers = split_footers(message)
+  top_lines, footer_lines, _ = split_footers(message)
   if not footer_lines:
     if not top_lines or top_lines[-1] != '':
       top_lines.append('')
     footer_lines = [new_footer]
-  elif not after_keys:
-    footer_lines.append(new_footer)
   else:
-    after_keys = set(map(normalize_name, after_keys))
-    # Iterate from last to first footer till we find the footer keys above.
-    for i, (key, _) in reversed(list(enumerate(parsed_footers))):
-      if normalize_name(key) in after_keys:
-        footer_lines.insert(i + 1, new_footer)
-        break
+    after_keys = set(map(normalize_name, after_keys or []))
+    after_indices = [
+        footer_lines.index(x) for x in footer_lines for k in after_keys
+        if normalize_name(parse_footer(x)[0]) == k]
+    before_keys = set(map(normalize_name, before_keys or []))
+    before_indices = [
+        footer_lines.index(x) for x in footer_lines for k in before_keys
+        if normalize_name(parse_footer(x)[0]) == k]
+    if after_indices:
+      # after_keys takes precedence, even if there's a conflict.
+      insert_idx = max(after_indices) + 1
+    elif before_indices:
+      insert_idx = min(before_indices)
     else:
-      footer_lines.insert(0, new_footer)
+      insert_idx = len(footer_lines)
+    footer_lines.insert(insert_idx, new_footer)
   return '\n'.join(top_lines + footer_lines)
 
 

tests/git_footers_test.py

@@ -81,8 +81,8 @@ My commit message is my best friend. It is my life. I must master it.
         'header-only\n\nChange-Id: Ixxx')
 
     self.assertEqual(
-        git_footers.add_footer_change_id('header\n\nsome: footter', 'Ixxx'),
-        'header\n\nChange-Id: Ixxx\nsome: footter')
+        git_footers.add_footer_change_id('header\n\nsome: footer', 'Ixxx'),
+        'header\n\nsome: footer\nChange-Id: Ixxx')
 
     self.assertEqual(
         git_footers.add_footer_change_id('header\n\nBUG: yy', 'Ixxx'),
@@ -94,7 +94,7 @@ My commit message is my best friend. It is my life. I must master it.
 
     self.assertEqual(
         git_footers.add_footer_change_id('header\n\nBUG: yy\n\nPos: 1', 'Ixxx'),
-        'header\n\nBUG: yy\n\nChange-Id: Ixxx\nPos: 1')
+        'header\n\nBUG: yy\n\nPos: 1\nChange-Id: Ixxx')
 
     # Special case: first line is never a footer, even if it looks line one.
     self.assertEqual(
@@ -116,7 +116,7 @@ My commit message is my best friend. It is my life. I must master it.
     self.assertEqual(
         git_footers.add_footer('Top\n\nSome: footer', 'Key', 'value',
                                after_keys=['Any']),
-        'Top\n\nKey: value\nSome: footer')
+        'Top\n\nSome: footer\nKey: value')
 
     self.assertEqual(
         git_footers.add_footer('Top\n\nSome: footer', 'Key', 'value',
@@ -128,6 +128,23 @@ My commit message is my best friend. It is my life. I must master it.
                                 'Key', 'value', after_keys=['Some']),
          'Top\n\nSome: footer\nKey: value\nOther: footer')
 
+    self.assertEqual(
+         git_footers.add_footer('Top\n\nSome: footer\nOther: footer',
+                                'Key', 'value', before_keys=['Other']),
+         'Top\n\nSome: footer\nKey: value\nOther: footer')
+
+    self.assertEqual(
+        git_footers.add_footer(
+              'Top\n\nSome: footer\nOther: footer\nFinal: footer',
+              'Key', 'value', after_keys=['Some'], before_keys=['Final']),
+        'Top\n\nSome: footer\nKey: value\nOther: footer\nFinal: footer')
+
+    self.assertEqual(
+        git_footers.add_footer(
+              'Top\n\nSome: footer\nOther: footer\nFinal: footer',
+              'Key', 'value', after_keys=['Other'], before_keys=['Some']),
+        'Top\n\nSome: footer\nOther: footer\nKey: value\nFinal: footer')
+
   def testReadStdin(self):
     self.mock(git_footers.sys, 'stdin', StringIO.StringIO(
         'line\r\notherline\r\n\r\n\r\nFoo: baz'))