supersize: Fix diff logic for changed vs unchanged of groups

tools/binary_size/libsupersize/describe.py

Index: tools/binary_size/libsupersize/describe.py
diff --git a/tools/binary_size/libsupersize/describe.py b/tools/binary_size/libsupersize/describe.py
index d7bf827480b6bcf322319b4d54752aa00e80dbb8..78a91e066dcfaa3a1c05a0bc68fc49c9f3dc7c8e 100644
--- a/tools/binary_size/libsupersize/describe.py
+++ b/tools/binary_size/libsupersize/describe.py
@@ -10,6 +10,9 @@ import time
 import models
 
 
+_DIFF_PREFIX_BY_STATUS = ['= ', '~ ', '+ ', '- ']
+
+
 def _PrettySize(size):
   # Arbitrarily chosen cut-off.
   if abs(size) < 2000:
@@ -42,16 +45,6 @@ def _FormatPss(pss):
   return ret
 
 
-def _DiffPrefix(diff, sym):
-  if diff.IsAdded(sym):
-    return '+ '
-  if diff.IsRemoved(sym):
-    return '- '
-  if sym.size:
-    return '~ '
-  return '= '
-
-
 def _Divide(a, b):
   return float(a) / b if b else 0
 
@@ -139,7 +132,7 @@ class Describer(object):
           yield '{} {}'.format(' ' * indent_size, l)
         else:
           if is_diff:
-            diff_prefix = _DiffPrefix(group, s)
+            diff_prefix = _DIFF_PREFIX_BY_STATUS[group.DiffStatus(s)]
           yield '{}{}{:<4} {:>8} {:7} {}'.format(
               indent_prefix, diff_prefix, str(index) + ')',
               _FormatPss(running_total), '({:.1%})'.format(running_percent), l)
@@ -182,6 +175,38 @@ class Describer(object):
     children_desc = self._DescribeSymbolGroupChildren(group)
     return itertools.chain(header_desc, children_desc)
 
+  def _DescribeDiffObjectPaths(self, diff):
+    paths_by_status = [set(), set(), set(), set()]
+    def helper(group):
+      for s in group:
+        if s.IsGroup():
+          helper(s)
+        else:
+          status = group.DiffStatus(s)
+          paths_by_status[status].add(s.source_path or s.object_path)
+    helper(diff)
+    # Show only paths that have no changed symbols (pure adds / removes).
+    unchanged, changed, added, removed = paths_by_status
+    added.difference_update(unchanged)
+    added.difference_update(changed)
+    removed.difference_update(unchanged)
+    removed.difference_update(changed)
+    yield '{} paths added, {} removed, {} changed'.format(
+        len(added), len(removed), len(changed))
+
+    if self.verbose and len(added):
+      yield 'Added files:'
+      for p in sorted(added):
+        yield '  ' + p
+    if self.verbose and len(removed):
+      yield 'Removed files:'
+      for p in sorted(removed):
+        yield '  ' + p
+    if self.verbose and len(changed):
+      yield 'Changed files:'
+      for p in sorted(changed):
+        yield '  ' + p
+
   def _DescribeSymbolDiff(self, diff):
     header_template = ('{} symbols added (+), {} changed (~), {} removed (-), '
                        '{} unchanged ({})')
@@ -189,27 +214,7 @@ class Describer(object):
     symbol_delta_desc = [header_template.format(
         diff.added_count, diff.changed_count, diff.removed_count,
         diff.unchanged_count, unchanged_msg)]
-
-    similar_paths = set()
-    added_paths = set()
-    removed_paths = set()
-    for s in diff:
-      if diff.IsAdded(s):
-        added_paths.add(s.object_path)
-      elif diff.IsRemoved(s):
-        removed_paths.add(s.object_path)
-      else:
-        similar_paths.add(s.object_path)
-    added_paths.difference_update(similar_paths)
-    removed_paths.difference_update(similar_paths)
-    path_delta_desc = ['{} object files added, {} removed'.format(
-        len(added_paths), len(removed_paths))]
-    if self.verbose and len(added_paths):
-      path_delta_desc.append('Added files:')
-      path_delta_desc.extend('  ' + p for p in sorted(added_paths))
-    if self.verbose and len(removed_paths):
-      path_delta_desc.append('Removed files:')
-      path_delta_desc.extend('  ' + p for p in sorted(removed_paths))
+    path_delta_desc = self._DescribeDiffObjectPaths(diff)
 
     diff = diff if self.verbose else diff.WhereNotUnchanged()
     group_desc = self._DescribeSymbolGroup(diff)