Fix issue #40: separate out fix_execfile and fix_cmp

Author: edschofield

docs/whatsnew.rst

@@ -135,9 +135,9 @@ On Python 3, as usual, ``object`` simply points to ``builtins.object``.
 past.builtins
 -------------
 The ``past.builtins`` package has been extended to add Py3 support for
-additional Py2 constructs that are not adequately handled by ``lib2to3`` (see upstream bug #). This
-includes custom ``execfile()`` and ``cmp()`` functions. ``futurize`` now
-invokes imports of these functions from ``past.builtins``.
+additional Py2 constructs that are not adequately handled by ``lib2to3`` (see
+upstream bug #). This includes custom ``execfile()`` and ``cmp()`` functions.
+``futurize`` now invokes imports of these functions from ``past.builtins``.
 
 
 Relative imports from Cython modules

libfuturize/fixes/__init__.py

@@ -75,6 +75,7 @@
 
 libfuturize_fix_names_stage2 = set([
     # 'libfuturize.fixes.fix_add__future__imports_except_unicode_literals',  # just in case
+    'libfuturize.fixes.fix_cmp',
     'libfuturize.fixes.fix_execfile',
     'libfuturize.fixes.fix_future_builtins',
     'libfuturize.fixes.fix_future_standard_library',

libfuturize/fixes/fix_cmp.py

@@ -0,0 +1,34 @@
+# coding: utf-8
+"""
+Fixer for the cmp() function on Py2, which was removed in Py3.
+
+Adds this import line::
+
+    from past.builtins import cmp
+
+if cmp() is called in the code.
+"""
+
+from __future__ import unicode_literals
+from lib2to3 import fixer_base
+
+from libfuturize.fixer_util import touch_import_top
+
+
+expression = "name='cmp'"
+
+
+class FixCmp(fixer_base.BaseFix):
+    BM_compatible = True
+    run_order = 9
+
+    PATTERN = """
+              power<
+                 ({0}) trailer< '(' args=[any] ')' >
+              rest=any* >
+              """.format(expression)
+
+    def transform(self, node, results):
+        name = results["name"]
+        touch_import_top(u'past.builtins', name.value, node)
+

libfuturize/fixes/fix_execfile.py

@@ -8,26 +8,18 @@
 
 Adds this import line::
 
-    from past.builtins import cmp
     from past.builtins import execfile
 
-for each of the functions cmp, execfile that were removed from Py3.
-
-Adds these imports after any other imports (in an initial block of them).
+for the function execfile() that was removed from Py3.
 """
 
 from __future__ import unicode_literals
-
 from lib2to3 import fixer_base
-from lib2to3.pygram import python_symbols as syms
-from lib2to3.fixer_util import Name, Call, in_special_context
 
 from libfuturize.fixer_util import touch_import_top
 
 
-replaced_builtins = '''cmp execfile'''.split()
-
-expression = '|'.join(["name='{0}'".format(name) for name in replaced_builtins])
+expression = "name='execfile'"
 
 
 class FixExecfile(fixer_base.BaseFix):