Track the modified code in a more fine-grained fashion

my2to3/fixes/fix_division_trace.py

@@ -12,6 +12,8 @@ from my2to3.util import parse_type
 
 
 trace = create_table("division", "filename", "lineno", "id", "dividend_type", "divisor_type")
+trace_modified = create_table("division_modified", "filename", "lineno", "id")
+
 
 @register_tracing_function
 def division_traced(id, dividend, divisor):
@@ -72,10 +74,13 @@ class FixDivisionTrace(BaseFix):
         comma = lib2to3.fixer_util.Comma()
         comma.prefix = children[1].prefix
 
+        id_ = self.ids[lineno]
+        trace_modified(self.filename, lineno, id_)
+
         new_node = lib2to3.fixer_util.Call(
           lib2to3.fixer_util.Name("division_traced"),
           args=(
-            lib2to3.fixer_util.Number(self.ids[lineno]),
+            lib2to3.fixer_util.Number(id_),
             lib2to3.fixer_util.Comma(),
             dividend,
             comma,

my2to3/trace.py

@@ -43,23 +43,17 @@ def get_fixers():
     f for f in get_fixers_from_package("my2to3.fixes") if f.endswith("_trace")
   ]
 
-
-trace_modified = create_table("modified", "fixer", "filename")
 def apply_fixers(string, name):
   # This function is inspired by refactoring_tool.refactor_file
 
-  encoding = tokenize.detect_encoding(lambda: string)[0]
-  string = string.decode(encoding) + u"\n" # '\n' to silence certain parse errors
-
-  for fixer in get_fixers():
-    refactoring_tool = RefactoringTool(fixer_names=[fixer])
-    tree = refactoring_tool.refactor_string(string, name)
-    if tree.was_changed:
-      trace_modified(fixer[17:-6], name)
-      string = unicode(tree)
+  refactoring_tool = RefactoringTool(fixer_names=get_fixers())
 
+  s = string + "\n" # Silence certain parse errors
+  encoding = tokenize.detect_encoding(lambda: s)[0]
+  s = s.decode(encoding)
+  s = unicode(refactoring_tool.refactor_string(s, name))
   # The [:-1] is to take off the \n we added earlier
-  return string[:-1].encode(encoding)
+  return s[:-1].encode(encoding)
 
 
 init_py = '__init__' + os.extsep + 'py'