An interactive tool to help find owners covering current change list.

owners.py

 # Copyright (c) 2012 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.
 
 """A database of OWNERS files.
 
 OWNERS files indicate who is allowed to approve changes in a specific directory
 (or who is allowed to make changes without needing approval of another OWNER).
 Note that all changes must still be reviewed by someone familiar with the code,
 so you may need approval from both an OWNER and a reviewer in many cases.
@@ skipping 60 matching lines @@
 
 
 class SyntaxErrorInOwnersFile(Exception):
   def __init__(self, path, lineno, msg):
     super(SyntaxErrorInOwnersFile, self).__init__((path, lineno, msg))
     self.path = path
     self.lineno = lineno
     self.msg = msg
 
   def __str__(self):
-    return "%s:%d syntax error: %s" % (self.path, self.lineno, self.msg)
+    return '%s:%d syntax error: %s' % (self.path, self.lineno, self.msg)
 
 
 class Database(object):
   """A database of OWNERS files for a repository.
 
   This class allows you to find a suggested set of reviewers for a list
   of changed files, and see if a list of changed files is covered by a
   list of reviewers."""
 
   def __init__(self, root, fopen, os_path, glob):
@@ skipping 12 matching lines @@
 
     # Pick a default email regexp to use; callers can override as desired.
     self.email_regexp = re.compile(BASIC_EMAIL_REGEXP)
 
     # Mapping of owners to the paths they own.
     self.owned_by = {EVERYONE: set()}
 
     # Mapping of paths to authorized owners.
     self.owners_for = {}
 
+    # Mapping reviewers to the preceding comment per file in the OWNERS files.
+    self.comments = {}
+
     # Set of paths that stop us from looking above them for owners.
     # (This is implicitly true for the root directory).
     self.stop_looking = set([''])
 
   def reviewers_for(self, files, author):
     """Returns a suggested set of reviewers that will cover the files.
 
     files is a sequence of paths relative to (and under) self.root.
     If author is nonempty, we ensure it is not included in the set returned
     in order avoid suggesting the author as a reviewer for their own changes."""
     self._check_paths(files)
-    self._load_data_needed_for(files)
+    self.load_data_needed_for(files)
     suggested_owners = self._covering_set_of_owners_for(files, author)
     if EVERYONE in suggested_owners:
       if len(suggested_owners) > 1:
         suggested_owners.remove(EVERYONE)
       else:
         suggested_owners = set(['<anyone>'])
     return suggested_owners
 
   def files_not_covered_by(self, files, reviewers):
     """Returns the files not owned by one of the reviewers.
 
     Args:
         files is a sequence of paths relative to (and under) self.root.
         reviewers is a sequence of strings matching self.email_regexp.
     """
     self._check_paths(files)
     self._check_reviewers(reviewers)
-    self._load_data_needed_for(files)
+    self.load_data_needed_for(files)
 
     covered_objs = self._objs_covered_by(reviewers)
     uncovered_files = [f for f in files
                        if not self._is_obj_covered_by(f, covered_objs)]
 
     return set(uncovered_files)
 
   def _check_paths(self, files):
     def _is_under(f, pfx):
       return self.os_path.abspath(self.os_path.join(pfx, f)).startswith(pfx)
@@ skipping 21 matching lines @@
 
   def _enclosing_dir_with_owners(self, objname):
     """Returns the innermost enclosing directory that has an OWNERS file."""
     dirpath = objname
     while not dirpath in self.owners_for:
       if self._stop_looking(dirpath):
         break
       dirpath = self.os_path.dirname(dirpath)
     return dirpath
 
-  def _load_data_needed_for(self, files):
+  def load_data_needed_for(self, files):
     for f in files:
       dirpath = self.os_path.dirname(f)
       while not dirpath in self.owners_for:
         self._read_owners_in_dir(dirpath)
         if self._stop_looking(dirpath):
           break
         dirpath = self.os_path.dirname(dirpath)
 
   def _read_owners_in_dir(self, dirpath):
     owners_path = self.os_path.join(self.root, dirpath, 'OWNERS')
     if not self.os_path.exists(owners_path):
       return
-
+    comment = []
+    in_comment = False
     lineno = 0
     for line in self.fopen(owners_path):
       lineno += 1
       line = line.strip()
-      if line.startswith('#') or line == '':
+      if line.startswith('#'):
+        if not in_comment:
+          comment = []
+        comment.append(line[1:].strip())
+        in_comment = True
         continue
+      if line == '':
+        continue
+      in_comment = False
+
       if line == 'set noparent':
         self.stop_looking.add(dirpath)
         continue
 
-      m = re.match("per-file (.+)=(.+)", line)
+      m = re.match('per-file (.+)=(.+)', line)
       if m:
         glob_string = m.group(1).strip()
         directive = m.group(2).strip()
         full_glob_string = self.os_path.join(self.root, dirpath, glob_string)
         if '/' in glob_string or '\\' in glob_string:
           raise SyntaxErrorInOwnersFile(owners_path, lineno,
               'per-file globs cannot span directories or use escapes: "%s"' %
               line)
         baselines = self.glob(full_glob_string)
         for baseline in (self.os_path.relpath(b, self.root) for b in baselines):
-          self._add_entry(baseline, directive, "per-file line",
-                          owners_path, lineno)
+          self._add_entry(baseline, directive, 'per-file line',
+                          owners_path, lineno, '\n'.join(comment))
         continue
 
       if line.startswith('set '):
         raise SyntaxErrorInOwnersFile(owners_path, lineno,
             'unknown option: "%s"' % line[4:].strip())
 
-      self._add_entry(dirpath, line, "line", owners_path, lineno)
+      self._add_entry(dirpath, line, 'line', owners_path, lineno,
+                      ' '.join(comment))
 
-  def _add_entry(self, path, directive, line_type, owners_path, lineno):
-    if directive == "set noparent":
+  def _add_entry(self, path, directive,
+                 line_type, owners_path, lineno, comment):
+    if directive == 'set noparent':
       self.stop_looking.add(path)
     elif self.email_regexp.match(directive) or directive == EVERYONE:
+      self.comments.setdefault(directive, {})
+      self.comments[directive][path] = comment
       self.owned_by.setdefault(directive, set()).add(path)
       self.owners_for.setdefault(path, set()).add(directive)
     else:
       raise SyntaxErrorInOwnersFile(owners_path, lineno,
           ('%s is not a "set" directive, "*", '
            'or an email address: "%s"' % (line_type, directive)))
 
   def _covering_set_of_owners_for(self, files, author):
     dirs_remaining = set(self._enclosing_dir_with_owners(f) for f in files)
-    all_possible_owners = self._all_possible_owners(dirs_remaining, author)
+    all_possible_owners = self.all_possible_owners(dirs_remaining, author)
     suggested_owners = set()
     while dirs_remaining:
       owner = self.lowest_cost_owner(all_possible_owners, dirs_remaining)
       suggested_owners.add(owner)
       dirs_to_remove = set(el[0] for el in all_possible_owners[owner])
       dirs_remaining -= dirs_to_remove
     return suggested_owners
 
-  def _all_possible_owners(self, dirs, author):
+  def all_possible_owners(self, dirs, author):
     """Returns a list of (potential owner, distance-from-dir) tuples; a
     distance of 1 is the lowest/closest possible distance (which makes the
     subsequent math easier)."""
     all_possible_owners = {}
     for current_dir in dirs:
       dirname = current_dir
       distance = 1
       while True:
         for owner in self.owners_for.get(dirname, []):
           if author and owner == author:
             continue
           all_possible_owners.setdefault(owner, [])
           # If the same person is in multiple OWNERS files above a given
           # directory, only count the closest one.
           if not any(current_dir == el[0] for el in all_possible_owners[owner]):
             all_possible_owners[owner].append((current_dir, distance))
         if self._stop_looking(dirname):
           break
         dirname = self.os_path.dirname(dirname)
         distance += 1
     return all_possible_owners
 
   @staticmethod
-  def lowest_cost_owner(all_possible_owners, dirs):
+  def total_costs_by_owner(all_possible_owners, dirs):
     # We want to minimize both the number of reviewers and the distance
     # from the files/dirs needing reviews. The "pow(X, 1.75)" below is
     # an arbitrarily-selected scaling factor that seems to work well - it
     # will select one reviewer in the parent directory over three reviewers
     # in subdirs, but not one reviewer over just two.
-    total_costs_by_owner = {}
+    result = {}
     for owner in all_possible_owners:
       total_distance = 0
       num_directories_owned = 0
       for dirname, distance in all_possible_owners[owner]:
         if dirname in dirs:
           total_distance += distance
           num_directories_owned += 1
-        if num_directories_owned:
-          total_costs_by_owner[owner] = (total_distance /
-                                         pow(num_directories_owned, 1.75))
+      if num_directories_owned:
+        result[owner] = (total_distance /
+                         pow(num_directories_owned, 1.75))
+    return result
 
+  @staticmethod
+  def lowest_cost_owner(all_possible_owners, dirs):
+    total_costs_by_owner = Database.total_costs_by_owner(all_possible_owners,
+                                                         dirs)
     # Return the lowest cost owner. In the case of a tie, pick one randomly.
     lowest_cost = min(total_costs_by_owner.itervalues())
     lowest_cost_owners = filter(
-      lambda owner: total_costs_by_owner[owner] == lowest_cost,
-      total_costs_by_owner)
+        lambda owner: total_costs_by_owner[owner] == lowest_cost,
+        total_costs_by_owner)
     return random.Random().choice(lowest_cost_owners)