Attempt to prevent imports from the python-future source directory from failing on Py3

Author: edschofield

_dummy_thread/__init__.py

@@ -1,8 +1,10 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
+__future_module__ = True
 
-if PY3:
-    from _dummy_thread import *
-else:
-    __future_module__ = True
+if sys.version_info[0] < 3:
     from dummy_thread import *
+else:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('_dummy_thread'):
+        from _dummy_thread import *

_markupbase/__init__.py

@@ -1,8 +1,10 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
+__future_module__ = True
 
-if PY3:
-    from _markupbase import *
-else:
-    __future_module__ = True
+if sys.version_info[0] < 3:
     from markupbase import *
+else:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('_markupbase'):
+        from _markupbase import *

_thread/__init__.py

@@ -1,8 +1,10 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
+__future_module__ = True
 
-if PY3:
-    from _thread import *
+if sys.version_info[0] < 3:
+    from dummy_thread import *
 else:
-    __future_module__ = True
-    from thread import *
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('_dummy_thread'):
+        from _dummy_thread import *

builtins/__init__.py

@@ -1,10 +1,12 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
+__future_module__ = True
 
-if PY3:
-    from builtins import *
-else:
-    __future_module__ = True
+if sys.version_info[0] < 3:
     from __builtin__ import *
     # Overwrite any old definitions with the equivalent future.builtins ones:
     from future.builtins import *
+else:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('builtins'):
+        from builtins import *

configparser/__init__.py

@@ -1,8 +1,9 @@
 from __future__ import absolute_import
+import sys
 
-from future.utils import PY2
-
-if PY2:
+if sys.version_info[0] < 3:
     from ConfigParser import *
 else:
-    from configparser import *
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('configparser'):
+        from configparser import *

future/standard_library/__init__.py

@@ -733,3 +733,48 @@ def from_import(module_name, *symbol_names, **kwargs):
         else:
             return output
 
+
+class exclude_local_folder_imports(object):
+    """
+    A context-manager that prevents standard library modules like configparser
+    from being imported from the local python-future source folder on Py3.
+
+    (The presence of a configparser folder would otherwise prevent setuptools
+    from running on Py3.)
+    """
+    def __init__(self, *args):
+        assert len(args) > 0
+        self.module_names = args
+
+    def __enter__(self):
+        self.old_sys_path = copy.copy(sys.path)
+        self.old_sys_modules = copy.copy(sys.modules)
+        if sys.version_info[0] < 3:
+            return
+        FUTURE_SOURCE_SUBFOLDERS = ['future', 'past', 'libfuturize', 'configparser']
+
+        # Look for the future source folder:
+        for folder in self.old_sys_path:
+            if all([os.path.exists(os.path.join(folder, subfolder))
+                    for subfolder in FUTURE_SOURCE_SUBFOLDERS]):
+                # Found it. Remove it.
+                sys.path.remove(folder)
+
+        # Ensure we import the system module:
+        for m in self.module_names:
+            try:
+                del sys.modules[m]
+            except KeyError:
+                pass
+            try:
+                module = __import__(m, level=0)
+            except ImportError:
+                # There's a problem importing the system module. E.g. the
+                # winreg module is not available except on Windows.
+                pass
+
+    def __exit__(self, *args):
+        # Restore sys.path and sys.modules:
+        sys.path = self.old_sys_path
+        for m in set(self.old_sys_modules.keys()) - set(sys.modules.keys()):
+            sys.modules[m] = self.old_sys_modules[m]

future/tests/test_standard_library.py

@@ -445,7 +445,8 @@ def test_install_aliases(self):
 
         from sys import intern
 
-        import test.support
+        # test_support may not be available (e.g. on Anaconda Py2.6):
+        # import test.support
 
         import urllib.error
         import urllib.parse

html/__init__.py

@@ -1,10 +1,12 @@
-from __future__ import absolute_import, unicode_literals
-from future.utils import PY3
+from __future__ import absolute_import
+import sys
+__future_module__ = True
 
-if PY3:
-    from html import *
+if sys.version_info[0] == 3:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('html'):
+        from html import *
 else:
-    __future_module__ = True
 
     # cgi.escape isn't good enough for the single Py3.3 html test to pass.
     # Define it inline here instead. From the Py3.3 stdlib

http/__init__.py

@@ -1,4 +1,10 @@
-from future.utils import PY3
+from __future__ import absolute_import
+import sys
+__future_module__ = True
 
-if not PY3:
-    __future_module__ = True
+if sys.version_info[0] < 3:
+    pass
+else:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('http'):
+        from http import *

http/server.py

@@ -1,8 +1,11 @@
 from __future__ import absolute_import
-from future.utils import PY3
+import sys
+__future_module__ = True
 
-if PY3:
-    from http.server import *
+if sys.version_info[0] == 3:
+    from future.standard_library import exclude_local_folder_imports
+    with exclude_local_folder_imports('http.server'):
+        from http.server import *
 else:
     __future_module__ = True
     from BaseHTTPServer import *