Add coverage statistic

tools/checkteamtags/owners_file_tags.py

Index: tools/checkteamtags/owners_file_tags.py
diff --git a/tools/checkteamtags/owners_file_tags.py b/tools/checkteamtags/owners_file_tags.py
index fc8d1f57ebc5ecb8a8d315aa2f0819f75e34061f..d2e3fe968e17ec8822e9b41651aa163dd37bd169 100644
--- a/tools/checkteamtags/owners_file_tags.py
+++ b/tools/checkteamtags/owners_file_tags.py
@@ -39,11 +39,26 @@ def aggregate_components_from_owners(root):
     root (str): the path to the src directory.
 
   Returns:
-    A pair (data, warnings) where data is a dict of the form
+    A tuple (data, warnings, errors, stats) where data is a dict of the form
       {'component-to-team': {'Component1': 'team1@chr...', ...},
        'dir-to-component': {'/path/to/1': 'Component1', ...}}
-      and warnings is a list of strings.
+      , warnings is a list of strings, stats is a dict of form
+      {'OWNERS-count': total number of OWNERS files,
+       'OWNERS-with-component-only-count': number of OWNERS have # COMPONENT,
+       'OWNERS-with-team-and-component-count': number of
+                          OWNERS have TEAM and COMPONENT,
+       'OWNERS-count-by-depth': {directory depth: number of OWNERS},
+       'OWNERS-with-component-only-count-by-depth': {directory depth: number
+                          of OWNERS have COMPONENT at this depth},
+       'OWNERS-with-team-and-component-count-by-depth':{directory depth: ...}}
   """
+  stats = {}
+  num_total = 0
+  num_with_component = 0
+  num_with_team_component = 0
+  num_total_by_depth = defaultdict(int)
+  num_with_component_by_depth = defaultdict(int)
+  num_with_team_component_by_depth = defaultdict(int)
   warnings = []
   component_to_team = defaultdict(set)
   dir_to_component = {}
@@ -51,19 +66,34 @@ def aggregate_components_from_owners(root):
     # Proofing against windows casing oddities.
     owners_file_names = [f for f in files if f.upper() == 'OWNERS']
     if owners_file_names:
+      file_depth = dirname[len(root) + len(os.path.sep):].count(os.path.sep)
+      num_total += 1
+      num_total_by_depth[file_depth] += 1
       owners_full_path = os.path.join(dirname, owners_file_names[0])
       owners_rel_path = os.path.relpath(owners_full_path, root)
       team, component = parse(owners_full_path)
       if component:
+        num_with_component += 1
+        num_with_component_by_depth[file_depth] += 1
         dir_to_component[os.path.relpath(dirname, root)] = component
         if team:
+          num_with_team_component += 1
+          num_with_team_component_by_depth[file_depth] += 1
           component_to_team[component].add(team)
       else:
         warnings.append('%s has no COMPONENT tag' % owners_rel_path)
   mappings = {'component-to-team': component_to_team,
               'dir-to-component': dir_to_component}
   errors = validate_one_team_per_component(mappings)
-  return unwrap(mappings), warnings, errors
+  stats = {'OWNERS-count': num_total,
+           'OWNERS-with-component-only-count': num_with_component,
+           'OWNERS-with-team-and-component-count': num_with_team_component,
+           'OWNERS-count-by-depth': num_total_by_depth,
+           'OWNERS-with-component-only-count-by-depth':
+           num_with_component_by_depth,
+           'OWNERS-with-team-and-component-count-by-depth':
+           num_with_team_component_by_depth}
+  return unwrap(mappings), warnings, errors, stats
 
 
 def validate_one_team_per_component(m):