Speed up importing of past.translation (issue #117)

Also: give more descriptive error messages if top-level packages are imported
somehow on Py3.

Author: edschofield

src/_dummy_thread/__init__.py

@@ -5,4 +5,6 @@
 if sys.version_info[0] < 3:
     from dummy_thread import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/_markupbase/__init__.py

@@ -5,4 +5,6 @@
 if sys.version_info[0] < 3:
     from markupbase import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/_thread/__init__.py

@@ -5,4 +5,6 @@
 if sys.version_info[0] < 3:
     from dummy_thread import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/builtins/__init__.py

@@ -7,4 +7,6 @@
     # Overwrite any old definitions with the equivalent future.builtins ones:
     from future.builtins import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/configparser/__init__.py

@@ -3,5 +3,11 @@
 
 if sys.version_info[0] < 3:
     from ConfigParser import *
+    try:
+        from ConfigParser import (_Chainmap, Error, InterpolationMissingOptionError)
+    except ImportError:
+        pass
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/copyreg/__init__.py

@@ -1,9 +1,9 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
 
-if PY3:
-    raise ImportError('Cannot import module from python-future source folder')
-    from copyreg import *
-else:
-    __future_module__ = True
+if sys.version_info[0] < 3:
     from copy_reg import *
+else:
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/future/standard_library/__init__.py

@@ -267,7 +267,7 @@ def load_module(self, name):
             # New name. Look up the corresponding old (Py2) name:
             oldname = self.new_to_old[name]
             module = self._find_and_load_module(oldname)
-            module.__future_module__ = True
+            # module.__future_module__ = True
         else:
             module = self._find_and_load_module(name)
         # In any case, make it available under the requested (Py3) name
@@ -451,7 +451,7 @@ def install_aliases():
         # We look up the module in sys.modules because __import__ just returns the
         # top-level package:
         newmod = sys.modules[newmodname]
-        newmod.__future_module__ = True
+        # newmod.__future_module__ = True
 
         __import__(oldmodname)
         oldmod = sys.modules[oldmodname]

src/html/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
-if sys.version_info[0] == 3:
-    raise ImportError('Cannot import module from python-future source folder')
-else:
+if sys.version_info[0] < 3:
     from future.moves.html import *
+else:
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/http/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
 if sys.version_info[0] < 3:
     pass
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/http/client.py

@@ -1,8 +1,6 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
-if sys.version_info[0] < 3:
-    from httplib import *
-else:
-    raise ImportError('Cannot import module from python-future source folder')
+assert sys.version_info[0] < 3
+
+from httplib import *

src/http/cookiejar.py

@@ -1,8 +1,6 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
 
-if PY3:
-    from http.cookiejar import *
-else:
-    __future_module__ = True
-    from cookielib import *
+assert sys.version_info[0] < 3
+
+from cookielib import *

src/http/cookies.py

@@ -1,9 +1,7 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
 
-if PY3:
-    from http.cookies import *
-else:
-    __future_module__ = True
-    from Cookie import *
-    from Cookie import Morsel    # left out of __all__ on Py2.7!
+assert sys.version_info[0] < 3
+
+from Cookie import *
+from Cookie import Morsel    # left out of __all__ on Py2.7!

src/http/server.py

@@ -1,21 +1,18 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
-if sys.version_info[0] == 3:
-    raise ImportError('Cannot import module from python-future source folder')
-else:
-    __future_module__ = True
-    from BaseHTTPServer import *
-    from CGIHTTPServer import *
-    from SimpleHTTPServer import *
+assert sys.version_info[0] < 3
+
+from BaseHTTPServer import *
+from CGIHTTPServer import *
+from SimpleHTTPServer import *
+try:
+    from CGIHTTPServer import _url_collapse_path     # needed for a test
+except ImportError:
     try:
-        from CGIHTTPServer import _url_collapse_path     # needed for a test
+        # Python 2.7.0 to 2.7.3
+        from CGIHTTPServer import (
+            _url_collapse_path_split as _url_collapse_path)
     except ImportError:
-        try:
-            # Python 2.7.0 to 2.7.3
-            from CGIHTTPServer import (
-                _url_collapse_path_split as _url_collapse_path)
-        except ImportError:
-            # Doesn't exist on Python 2.6.x. Ignore it.
-            pass
+        # Doesn't exist on Python 2.6.x. Ignore it.
+        pass

src/past/__init__.py

@@ -82,10 +82,8 @@
 ---------
 Copyright 2013-2014 Python Charmers Pty Ltd, Australia.
 The software is distributed under an MIT licence. See LICENSE.txt.
-
 """
 
-# from past.builtins import *
 
 from past.translation import install_hooks as autotranslate
 from future import __version__, __copyright__, __license__

src/past/translation/__init__.py

@@ -43,7 +43,6 @@
 
 from libfuturize import fixes
 
-__version__ = '0.1.0'
 
 logger = logging.getLogger(__name__)
 logger.setLevel(logging.DEBUG)
@@ -54,12 +53,6 @@
            list(fixes.lib2to3_fix_names_stage2))
 
 
-# There are two possible grammars: with or without the print statement.
-# Hence we have two possible refactoring tool implementations.
-_rt = RefactoringTool(myfixes)
-_rtp = RefactoringTool(myfixes, {'print_function': True})
-
-# 
 # We detect whether the code is Py2 or Py3 by applying certain lib2to3 fixers
 # to it. If the diff is empty, it's Python 3 code.
 
@@ -122,12 +115,42 @@
 ]
 
 
-_rt_py2_detect = RefactoringTool(py2_detect_fixers)
-_rtp_py2_detect = RefactoringTool(py2_detect_fixers,
-                                  {'print_function': True})
+class RTs:
+    """
+    A namespace for the refactoring tools. This avoids creating these at
+    the module level, which slows down the module import. (See issue #117).
+
+    There are two possible grammars: with or without the print statement.
+    Hence we have two possible refactoring tool implementations.
+    """
+    _rt = None
+    _rtp = None
+    _rt_py2_detect = None
+    _rtp_py2_detect = None
+
+    @staticmethod
+    def setup():
+        """
+        Call this before using the refactoring tools to create them on demand
+        if needed.
+        """
+        if None in [RTs._rt, RTs._rtp]:
+            RTs._rt = RefactoringTool(myfixes)
+            RTs._rtp = RefactoringTool(myfixes, {'print_function': True})
+
+
+    @staticmethod
+    def setup_detect_python2():
+        """
+        Call this before using the refactoring tools to create them on demand
+        if needed.
+        """
+        if None in [RTs._rt_py2_detect, RTs._rtp_py2_detect]:
+            RTs._rt_py2_detect = RefactoringTool(py2_detect_fixers)
+            RTs._rtp_py2_detect = RefactoringTool(py2_detect_fixers,
+                                                  {'print_function': True})
 
 
-#
 # We need to find a prefix for the standard library, as we don't want to
 # process any files there (they will already be Python 3).
 #
@@ -145,7 +168,6 @@
 # Instead, we use the portion of the path common to both the stdlib modules
 # ``math`` and ``urllib``.
 
-import os, sys
 def splitall(path):
     """
     Split a path into all components. From Python Cookbook.
@@ -179,21 +201,20 @@ def common_substring(s1, s2):
         chunks.append(dir1)
     return os.path.join(*chunks)
 
-# import math
-# import urllib
 # _stdlibprefix = common_substring(math.__file__, urllib.__file__)
 
 
 def detect_python2(source, pathname):
     """
     Returns a bool indicating whether we think the code is Py2
     """
+    RTs.setup_detect_python2()
     try:
-        tree = _rt_py2_detect.refactor_string(source, pathname)
+        tree = RTs._rt_py2_detect.refactor_string(source, pathname)
     except ParseError as e:
         if e.msg != 'bad input' or e.value != '=':
             raise
-        tree = _rtp.refactor_string(source, pathname)
+        tree = RTs._rtp.refactor_string(source, pathname)
 
     if source != str(tree)[:-1]:   # remove added newline
         # The above fixers made changes, so we conclude it's Python 2 code
@@ -282,13 +303,14 @@ def transform(self, source):
         # if that's better for you
 
         # lib2to3 likes a newline at the end
+        RTs.setup()
         source += '\n'
         try:
-            tree = _rt.refactor_string(source, self.pathname)
+            tree = RTs._rt.refactor_string(source, self.pathname)
         except ParseError as e:
             if e.msg != 'bad input' or e.value != '=':
                 raise
-            tree = _rtp.refactor_string(source, self.pathname)
+            tree = RTs._rtp.refactor_string(source, self.pathname)
         # could optimise a bit for only doing str(tree) if
         # getattr(tree, 'was_changed', False) returns True
         return str(tree)[:-1] # remove added newline

src/queue/__init__.py

@@ -5,4 +5,6 @@
 if sys.version_info[0] < 3:
     from Queue import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/reprlib/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
 if sys.version_info[0] < 3:
     from repr import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/socketserver/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
 if sys.version_info[0] < 3:
     from SocketServer import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/tkinter/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
 if sys.version_info[0] < 3:
     from Tkinter import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/winreg/__init__.py

@@ -5,4 +5,6 @@
 if sys.version_info[0] < 3:
     from _winreg import *
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/xmlrpc/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
 import sys
-__future_module__ = True
 
 if sys.version_info[0] < 3:
     pass
 else:
-    raise ImportError('Cannot import module from python-future source folder')
+    raise ImportError('This package should not be accessible on Python 3. '
+                      'Either you are trying to run from the python-future src folder '
+                      'or your installation of python-future is corrupted.')

src/xmlrpc/client.py

@@ -1,7 +1,5 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
 
-if PY3:
-    from xmlrpc.client import *
-else:
-    from xmlrpclib import *
+assert sys.version_info[0] < 3
+from xmlrpclib import *

src/xmlrpc/server.py

@@ -1,7 +1,5 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
 
-if PY3:
-    from xmlrpc.server import *
-else:
-    from xmlrpclib import *
+assert sys.version_info[0] < 3
+from xmlrpclib import *