fixes: major refactoring to eliminate boilerplate code

my2to3/fixes/__init__.py

@@ -2,14 +2,28 @@ from collections import defaultdict
 from lib2to3.fixer_base import BaseFix as lib2to3_BaseFix
 import lib2to3.fixer_util
 
+from my2to3.trace import create_table, get_data, tracing_functions
+
 
 class BaseFix(lib2to3_BaseFix):
-  def start_tree(self, tree, filename):
-    super(BaseFix, self).start_tree(tree, filename)
+  pass
+
+
+class BaseStaticTraceFix(BaseFix):
+  def __init__(self, *args, **kwargs):
+    super(BaseStaticTraceFix, self).__init__(*args, **kwargs)
+
+    # Note: id is used to differentiate the divisions of the same line.
+    shared_columns = "filename", "lineno", "id"
+    self.insert_trace = create_table(self.basename + "_trace", *(shared_columns + self.traced_information))
+    self.insert_modified = create_table(self.basename + "_modified", *shared_columns)
+
+  def start_tree(self, *args, **kwargs):
+    super(BaseStaticTraceFix, self).start_tree(*args, **kwargs)
 
     self.ids = defaultdict(int)
 
-  def traced_call(self, name, insert_function, node, children):
+  def traced_call(self, node, children):
     # Important: every node inside "children" should be cloned before this
     # function is called.
 
@@ -22,7 +36,7 @@ class BaseFix(lib2to3_BaseFix):
     id_ = self.ids[lineno]
 
     new_node = lib2to3.fixer_util.Call(
-      lib2to3.fixer_util.Name(name),
+      lib2to3.fixer_util.Name(self.basename + "_traced"),
       args=[
         lib2to3.fixer_util.String('"%s"' % filename),
         lib2to3.fixer_util.Comma(),
@@ -35,6 +49,50 @@ class BaseFix(lib2to3_BaseFix):
 
     self.ids[lineno] += 1
 
-    insert_function(filename, lineno, id_)
+    self.insert_modified(filename, lineno, id_)
 
     return new_node
+
+
+class BaseDynamicTraceFix(BaseStaticTraceFix):
+  def __init__(self, *args, **kwargs):
+    super(BaseDynamicTraceFix, self).__init__(*args, **kwargs)
+
+    def f(filename, lineno, id_, *args, **kwargs):
+      result, values = self._dynamic_trace(*args, **kwargs)
+      self.insert_trace(filename, lineno, id_, *values)
+      return result
+    f.__name__ = self.basename + "_traced"
+    tracing_functions.append(f)
+
+
+class BaseSupportFix(BaseFix):
+  def __init__(self, *args, **kwargs):
+    super(BaseSupportFix, self).__init__(*args, **kwargs)
+
+    # Note: id is used to differentiate the divisions of the same line.
+    self.insert_support = create_table(self.basename + "_support", "filename", "lineno", "id", "status")
+
+  def analyze_data(self, filename, lineno, id_):
+    class_name = "Fix%sTrace" % self.basename.capitalize()
+    traced_information = getattr(
+      __import__("my2to3.fixes.fix_%s_trace" % self.basename, fromlist=[class_name]),
+      class_name
+    ).traced_information
+
+    data = get_data(
+      self.basename + "_trace",
+      traced_information,
+      dict(filename=filename, lineno=lineno, id=id_)
+    )
+
+    if data:
+      try:
+        results, status = self._analyze_data()
+      except Exception:
+        results, status = False, "unknown"
+    else:
+      results, status = False, "no data"
+
+    self.insert_support(filename[1:-1], lineno, id_, status)
+    return results

my2to3/fixes/fix_division_support.py

@@ -3,36 +3,26 @@ from lib2to3.pygram import python_symbols as syms
 from lib2to3.pytree import Leaf, Node
 import os
 
-from . import BaseFix
-from my2to3.trace import create_table, get_data
+from . import BaseSupportFix
+from my2to3.trace import create_table
 from my2to3.util import add_future, data2types
 
 
-# id is used to differentiate the divisions of the same line.
-insert_support = create_table("division_support", "filename", "lineno", "id", "status")
-
-
-def analyze_data(data):
-  if not data:
-    return False, "no data"
+class FixDivisionSupport(BaseSupportFix):
+  """Rewrites division_traced(n, a, b) into Py2/Py3-compatible division
+  """
+  basename = "division"
 
-  try:
+  @staticmethod
+  def _analyze_data(data):
     types = data2types(data)
-  except Exception as e:
-    # Probably, one type is not a builtins
-    return False, "unknown"
 
-  if len(types) == 1:
-    dividend, divisor = types[0]
-    if dividend is divisor is int:
-      return True, "automatic"
+    if len(types) == 1:
+      dividend, divisor = types[0]
+      if dividend is divisor is int:
+        return True, "automatic"
 
-  return False, "manual"
-
-
-class FixDivisionSupport(BaseFix):
-  """Rewrites division_traced(n, a, b) into Py2/Py3-compatible division
-  """
+    return False, "manual"
 
   # Inspired by https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/lib2to3/fixes/fix_xrange.py#L14
   PATTERN = """
@@ -42,15 +32,7 @@ class FixDivisionSupport(BaseFix):
 
   def transform(self, node, results):
     args = results['args']
-    filename, lineno, id_ = [l.value for l in args.children[:-4:2]]
-    should_change, status = analyze_data(
-      get_data(
-        "division_trace",
-        ["dividend_type", "divisor_type"],
-        dict(filename=filename, lineno=lineno, id=id_)
-      )
-    )
-    insert_support(filename[1:-1], lineno, id_, status)
+    should_change = self.analyze_data(*[l.value for l in args.children[:-4:2]])
     if should_change:
       add_future(node, 'division')
       operator = Leaf(lib2to3.pgen2.token.DOUBLESLASH, "//")

my2to3/fixes/fix_division_trace.py

@@ -4,30 +4,22 @@ import lib2to3.pgen2
 from lib2to3.pygram import python_symbols as syms
 from lib2to3.pytree import Node
 
-from . import BaseFix
-from my2to3.trace import create_table, register_tracing_function
+from . import BaseDynamicTraceFix
 from my2to3.util import parse_type
 
 
-insert_trace = create_table("division_trace", "filename", "lineno", "id", "dividend_type", "divisor_type")
-insert_modified = create_table("division_modified", "filename", "lineno", "id")
-
-
-@register_tracing_function
-def division_traced(filename, lineno, id_, dividend, divisor):
-  insert_trace(
-    filename,
-    lineno,
-    id_,
-    parse_type(type(dividend)),
-    parse_type(type(divisor))
-  )
-  return dividend / divisor
-
-
-class FixDivisionTrace(BaseFix):
+class FixDivisionTrace(BaseDynamicTraceFix):
   """Rewrites a / b into division_traced(id, a, b)
   """
+  basename = "division"
+  traced_information = "dividend_type", "divisor_type"
+
+  @staticmethod
+  def _dynamic_trace(dividend, divisor):
+    return (
+      dividend / divisor,
+      (parse_type(type(dividend)), parse_type(type(divisor)))
+    )
 
   def match(self, node):
     if node.type == syms.term:
@@ -64,7 +56,7 @@ class FixDivisionTrace(BaseFix):
         comma.prefix = children[1].prefix
         children[1] = comma
 
-        previous_node = self.traced_call("division_traced", insert_modified, node, children)
+        previous_node = self.traced_call(node, children)
       else:
         # It's not a division operation
         previous_node = Node(syms.term, children)

my2to3/fixes/fix_nested_except_trace.py

 from lib2to3.pygram import python_symbols as syms
 
-from . import BaseFix
-from my2to3.trace import create_table
+from . import BaseStaticTraceFix
 
 
-insert_trace = create_table("nested_except_trace", "filename", "lineno_parent", "lineno_child")
-
-
-class FixNestedExceptTrace(BaseFix):
+class FixNestedExceptTrace(BaseStaticTraceFix):
   """This fixer detects scope bugs which can occur due to nested except clauses
   which use the same variable name.
 
@@ -33,6 +29,9 @@ class FixNestedExceptTrace(BaseFix):
       print(e)
     raise
   """
+  basename = "nested_except"
+  traced_information = "lineno_parent", "lineno_child"
+
   # https://github.com/python/cpython/blob/3549ca313a6103a3adb281ef3a849298b7d7f72c/Lib/lib2to3/fixes/fix_except.py#L39-L45
   PATTERN = """
   try_stmt< 'try' ':' (simple_stmt | suite)
@@ -59,6 +58,6 @@ class FixNestedExceptTrace(BaseFix):
     for child in self.list_except_clause_children(body):
       try:
         if except_clause.children[3] == child.children[3]:
-          insert_trace(self.filename, except_clause.get_lineno(), child.get_lineno())
+          self.insert_trace(self.filename, None, None, except_clause.get_lineno(), child.get_lineno())
       except Exception:
         pass

my2to3/fixes/fix_round_trace.py

@@ -4,30 +4,23 @@ import lib2to3.pgen2
 from lib2to3.pygram import python_symbols as syms
 from lib2to3.pytree import Node
 
-from . import BaseFix
-from my2to3.trace import create_table, register_tracing_function
+from . import BaseDynamicTraceFix
 from my2to3.util import parse_type
 
 
-insert_trace = create_table("round_trace", "filename", "lineno", "id", "number", "ndigits")
-insert_modified = create_table("round_modified", "filename", "lineno", "id")
-
-
-@register_tracing_function
-def round_traced(filename, lineno, id_, number, ndigits=0):
-  insert_trace(
-    filename,
-    lineno,
-    id_,
-    number,
-    ndigits
-  )
-  return round(number, ndigits)
-
-
-class FixRoundTrace(BaseFix):
+class FixRoundTrace(BaseDynamicTraceFix):
   """Rewrites round(a[, b]) into round_traced(id, a[, b])
   """
+  basename = "round"
+  traced_information = "number", "ndigits"
+
+  @staticmethod
+  def _dynamic_trace(number, ndigits=0):
+    return (
+      round(number, ndigits),
+      (parse_type(type(number)), parse_type(type(ndigits)))
+    )
+
   # Inspired by https://github.com/python/cpython/blob/e42b705188271da108de42b55d9344642170aa2b/Lib/lib2to3/fixes/fix_xrange.py#L14
   PATTERN = """
             power<'round' trailer< '(' args=any ')' >
@@ -45,4 +38,4 @@ class FixRoundTrace(BaseFix):
       # e.g. round(1,23, 4)
       children = [leaf.clone() for leaf in args.children]
 
-    node.replace(self.traced_call("division_traced", insert_modified, node, children))
+    node.replace(self.traced_call(node, children))

my2to3/tests/testFixNestedExceptTrace.py

@@ -30,7 +30,7 @@ class testFixNestedExceptTrace(FixerTestCase):
             3
         """
     self.unchanged(a)
-    self.assertDataEqual("nested_except_trace", [(u'<string>', 4, 7)])
+    self.assertDataEqual("nested_except_trace", [(u'<string>', None, None, 4, 7)])
 
   def test_except_2(self):
     a = """
@@ -59,7 +59,7 @@ class testFixNestedExceptTrace(FixerTestCase):
               4
         """
     self.unchanged(a)
-    self.assertDataEqual("nested_except_trace", [(u'<string>', 7, 10), (u'<string>', 4, 7), (u'<string>', 4, 10)])
+    self.assertDataEqual("nested_except_trace", [(u'<string>', None, None, 7, 10), (u'<string>', None, None, 4, 7), (u'<string>', None, None, 4, 10)])
 
   def test_else(self):
     a = """

my2to3/trace.py

@@ -8,9 +8,6 @@ conn = sqlite3.connect(database)
 
 
 tracing_functions = []
-def register_tracing_function(f):
-  tracing_functions.append(f)
-  return f
 
 
 def create_table(table, *columns):
@@ -115,11 +112,9 @@ class ModuleImporter:
 def patch_imports(whitelist):
   sys.meta_path.append(ModuleImporter(whitelist))
 
+  # XXX: This makes sure that "my2to3.trace.tracing_functions" is correctly
+  # populated. Let's find a better way.
+  apply_fixers("", "dummy")
+
   for f in tracing_functions:
     setattr(__builtin__, f.__name__, f)
-
-
-for fixer in get_fixers():
-  # Import each fixer, to make sure that "my2to3.trace.tracing_functions" is
-  # correctly populated.
-  __import__(fixer)