ShimImporter: implement modern interface

IPython/utils/shimmodule.py

@@ -3,6 +3,8 b''
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
+import importlib.abc
+import importlib.util
 import sys
 import types
 from importlib import import_module
@@ -13,41 +15,26 b' from .importstring import import_item'
 class ShimWarning(Warning):
     """A warning to show when a module has moved, and a shim is in its place."""
 
-class ShimImporter(object):
+
+class ShimImporter(importlib.abc.MetaPathFinder):
     """Import hook for a shim.
-    
+
     This ensures that submodule imports return the real target module,
     not a clone that will confuse `is` and `isinstance` checks.
     """
     def __init__(self, src, mirror):
         self.src = src
         self.mirror = mirror
-    
+
     def _mirror_name(self, fullname):
         """get the name of the mirrored module"""
-        
-        return self.mirror + fullname[len(self.src):]
 
-    def find_module(self, fullname, path=None):
-        """Return self if we should be used to import the module."""
-        if fullname.startswith(self.src + '.'):
-            mirror_name = self._mirror_name(fullname)
-            try:
-                mod = import_item(mirror_name)
-            except ImportError:
-                return
-            else:
-                if not isinstance(mod, types.ModuleType):
-                    # not a module
-                    return None
-                return self
+        return self.mirror + fullname[len(self.src) :]
 
-    def load_module(self, fullname):
-        """Import the mirrored module, and insert it into sys.modules"""
-        mirror_name = self._mirror_name(fullname)
-        mod = import_item(mirror_name)
-        sys.modules[fullname] = mod
-        return mod
+    def find_spec(self, fullname, path, target=None):
+        if fullname.startswith(self.src + "."):
+            mirror_name = self._mirror_name(fullname)
+            return importlib.util.find_spec(mirror_name)
 
 
 class ShimModule(types.ModuleType):

IPython/utils/tests/test_shimmodule.py

@@ -8,3 +8,7 b' def test_shim_warning():'
     sys.modules.pop('IPython.config', None)
     with pytest.warns(ShimWarning):
         import IPython.config
+
+    import traitlets.config
+
+    assert IPython.config.Config is traitlets.config.Config