To prevent another screw-up on my part where my prototype gets lost thanks to
an ``svn revert`` (gee, maybe more atomic commits by use of something like a DVCS would help with this? Wish someone would get on that ...), I am checking in an untested, work-in-progress meta path finder to handle sys.path.
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@ -589,6 +589,82 @@ class PyFileImporter(FileImporter):
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super(PyFileImporter, self).__init__(path_entry)
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class SysPathFinder:
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"""Meta path finder for sys.(path|path_hooks|path_importer_cache)."""
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def _default_hook(self, path):
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"""Use the default hook on 'path'.
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If the path will not work for the default hook then raise ImportError.
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"""
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# TODO(brett.cannon) Implement
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raise ImportError
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# The list of implicit hooks cannot be a class attribute because of
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# bootstrapping issues for accessing imp.
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def _implicit_hooks(self, path):
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"""Return a list of the implicit path hooks."""
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return [self._default_hook, imp.NullImporter]
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def _path_hooks(self, path):
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"""Search sys.path_hooks for a finder for 'path'.
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Guaranteed to return a finder for the path as NullImporter is the
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default importer for any path that does not have an explicit finder.
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"""
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for hook in sys.path_hooks + self._implicit_hooks():
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try:
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return hook(path)
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except ImportError:
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continue
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else:
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# This point should never be reached thanks to NullImporter.
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raise SystemError("no hook could find an importer for "
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"{0}".format(path))
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def _path_importer_cache(self, path):
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"""Get the finder for the path from sys.path_importer_cache.
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If the path is not in the cache, find the appropriate finder and cache
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it. If None is cached, get the default finder and cache that
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(if applicable).
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Because of NullImporter, some finder should be returned. The only
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explicit fail case is if None is cached but the path cannot be used for
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the default hook, for which ImportError is raised.
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"""
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try:
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finder = sys.path_importer_cache(path);
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except KeyError:
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finder = self._path_hooks(path)
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sys.path_importer_cache[path] = finder
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else:
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if finder is None:
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# Raises ImportError on failure.
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finder = self._default_hook(path)
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sys.path_importer_cache[path] = finder
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return finder
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def find_module(self, fullname, path=None):
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"""Find the module on sys.path or 'path'."""
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if not path:
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path = sys.path
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for entry in path:
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try:
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finder = self._path_importer_cache(entry)
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except ImportError:
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continue
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loader = finder.find_module(fullname)
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if loader:
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return loader
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else:
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return None
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class ImportLockContext(object):
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"""Context manager for the import lock."""
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