policy: drop custom importer for pure modules

mercurial/__init__.py

@@ -7,120 +7,16 b''
 
 from __future__ import absolute_import
 
-import imp
-import os
 import sys
-import zipimport
-
-from . import (
-    policy
-)
 
 __all__ = []
 
-modulepolicy = policy.policy
-
-# Modules that have both Python and C implementations. See also the
-# set of .py files under mercurial/pure/.
-_dualmodules = {
-}
-
-class hgimporter(object):
-    """Object that conforms to import hook interface defined in PEP-302."""
-    def find_module(self, name, path=None):
-        # We only care about modules that have both C and pure implementations.
-        if name in _dualmodules:
-            return self
-        return None
-
-    def load_module(self, name):
-        mod = sys.modules.get(name, None)
-        if mod:
-            return mod
-
-        mercurial = sys.modules['mercurial']
-
-        # The zip importer behaves sufficiently differently from the default
-        # importer to warrant its own code path.
-        loader = getattr(mercurial, '__loader__', None)
-        if isinstance(loader, zipimport.zipimporter):
-            def ziploader(*paths):
-                """Obtain a zipimporter for a directory under the main zip."""
-                path = os.path.join(loader.archive, *paths)
-                zl = sys.path_importer_cache.get(path)
-                if not zl:
-                    zl = zipimport.zipimporter(path)
-                return zl
-
-            try:
-                if modulepolicy in policy.policynoc:
-                    raise ImportError()
-
-                zl = ziploader('mercurial')
-                mod = zl.load_module(name)
-                # Unlike imp, ziploader doesn't expose module metadata that
-                # indicates the type of module. So just assume what we found
-                # is OK (even though it could be a pure Python module).
-            except ImportError:
-                if modulepolicy == b'c':
-                    raise
-                zl = ziploader('mercurial', 'pure')
-                mod = zl.load_module(name)
-
-            sys.modules[name] = mod
-            return mod
-
-        # Unlike the default importer which searches special locations and
-        # sys.path, we only look in the directory where "mercurial" was
-        # imported from.
-
-        # imp.find_module doesn't support submodules (modules with ".").
-        # Instead you have to pass the parent package's __path__ attribute
-        # as the path argument.
-        stem = name.split('.')[-1]
-
-        try:
-            if modulepolicy in policy.policynoc:
-                raise ImportError()
-
-            modinfo = imp.find_module(stem, mercurial.__path__)
-
-            # The Mercurial installer used to copy files from
-            # mercurial/pure/*.py to mercurial/*.py. Therefore, it's possible
-            # for some installations to have .py files under mercurial/*.
-            # Loading Python modules when we expected C versions could result
-            # in a) poor performance b) loading a version from a previous
-            # Mercurial version, potentially leading to incompatibility. Either
-            # scenario is bad. So we verify that modules loaded from
-            # mercurial/* are C extensions. If the current policy allows the
-            # loading of .py modules, the module will be re-imported from
-            # mercurial/pure/* below.
-            if modinfo[2][2] != imp.C_EXTENSION:
-                raise ImportError('.py version of %s found where C '
-                                  'version should exist' % name)
-
-        except ImportError:
-            if modulepolicy == b'c':
-                raise
-
-            # Could not load the C extension and pure Python is allowed. So
-            # try to load them.
-            from . import pure
-            modinfo = imp.find_module(stem, pure.__path__)
-            if not modinfo:
-                raise ImportError('could not find mercurial module %s' %
-                                  name)
-
-        mod = imp.load_module(name, *modinfo)
-        sys.modules[name] = mod
-        return mod
-
 # Python 3 uses a custom module loader that transforms source code between
 # source file reading and compilation. This is done by registering a custom
 # finder that changes the spec for Mercurial modules to use a custom loader.
 if sys.version_info[0] >= 3:
-    from . import pure
     import importlib
+    import importlib.abc
     import io
     import token
     import tokenize
@@ -135,14 +31,6 b' if sys.version_info[0] >= 3:'
             if fullname.startswith('mercurial.zstd'):
                 return None
 
-            # This assumes Python 3 doesn't support loading C modules.
-            if fullname in _dualmodules:
-                stem = fullname.split('.')[-1]
-                fullname = 'mercurial.pure.%s' % stem
-                target = pure
-                assert len(path) == 1
-                path = [os.path.join(path[0], 'pure')]
-
             # Try to find the module using other registered finders.
             spec = None
             for finder in sys.meta_path:
@@ -159,10 +47,6 b' if sys.version_info[0] >= 3:'
             if not spec:
                 return None
 
-            if (fullname.startswith('mercurial.pure.')
-                and fullname.replace('.pure.', '.') in _dualmodules):
-                spec.name = spec.name.replace('.pure.', '.')
-
             # TODO need to support loaders from alternate specs, like zip
             # loaders.
             spec.loader = hgloader(spec.name, spec.origin)
@@ -386,13 +270,10 b' if sys.version_info[0] >= 3:'
             # implemented them because they are very ugly.
             return super(hgloader, self).source_to_code(data, path)
 
-# We automagically register our custom importer as a side-effect of loading.
-# This is necessary to ensure that any entry points are able to import
-# mercurial.* modules without having to perform this registration themselves.
-if sys.version_info[0] >= 3:
-    _importercls = hgpathentryfinder
-else:
-    _importercls = hgimporter
-if not any(isinstance(x, _importercls) for x in sys.meta_path):
-    # meta_path is used before any implicit finders and before sys.path.
-    sys.meta_path.insert(0, _importercls())
+    # We automagically register our custom importer as a side-effect of
+    # loading. This is necessary to ensure that any entry points are able
+    # to import mercurial.* modules without having to perform this
+    # registration themselves.
+    if not any(isinstance(x, hgpathentryfinder) for x in sys.meta_path):
+        # meta_path is used before any implicit finders and before sys.path.
+        sys.meta_path.insert(0, hgpathentryfinder())