New fixer: fix_division

my2to3/fixes/fix_division.py

+import builtins
+from collections import defaultdict
+import lib2to3.fixer_base
+import os
+import re
+
+trace_file_match = re.compile(r"^(.*):(.*):(.*) <type '(.*)'> / <type '(.*)'>$").match
+
+
+def parse_trace_data(filepath):
+  def tree():
+    return defaultdict(tree)
+
+  traces = tree()
+  with open(filepath) as f:
+    for line in f:
+      file, lineno, id_, dividend_type, divisor_type = trace_file_match(line).groups()
+      lineno = int(lineno)
+      id_ = int(id_)
+      dividend_type = getattr(builtins, dividend_type)
+      divisor_type = getattr(builtins, divisor_type)
+
+      t = traces[file][lineno]
+      data = (dividend_type, divisor_type)
+      if id_ in t:
+        t[id_].add(data)
+      else:
+        t[id_] = {data}
+
+  return traces
+
+
+class FixDivision(lib2to3.fixer_base.BaseFix):
+  """Rewrites division_traced(n, a, b) into Py2/Py3-compatible division
+
+  The `TRACE_FILE` environment variable must point to the trace data file. See
+  `fix_trace_division.py` for more details.
+  """
+
+  traces = parse_trace_data(os.environ["TRACE_FILE"])
+
+  # Inspired by https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/lib2to3/fixes/fix_xrange.py#L14
+  PATTERN = """
+            power<'division_traced' trailer< '(' args=any ')' >
+            rest=any* >
+            """
+
+  def start_tree(self, tree, filename):
+    super(FixDivision, self).start_tree(tree, filename)
+
+    self.absolute_filename = os.path.abspath(filename)
+
+  def transform(self, node, results):
+    lineno = node.get_lineno()
+    id_ = int(node.children[1].children[1].children[0].value)
+
+    data = self.traces[self.absolute_filename][lineno][id_]
+
+    # TODO: analyse `data`, and replace the node to rewrite code