Refactor importlib to make it easier to re-implement in C.

Lib/importlib/_bootstrap.py

@@ -918,20 +918,12 @@ def _find_module(name, path):
         return None
 
 
-def _set___package__(module):
-    """Set __package__ on a module."""
-    # Watch out for what comes out of sys.modules to not be a module,
-    # e.g. an int.
-    try:
-        module.__package__ = module.__name__
-        if not hasattr(module, '__path__'):
-            module.__package__ = module.__package__.rpartition('.')[0]
-    except AttributeError:
-        pass
-
-
 def _sanity_check(name, package, level):
     """Verify arguments are "sane"."""
+    if not hasattr(name, 'rpartition'):
+        raise TypeError("module name must be str, not {}".format(type(name)))
+    if level < 0:
+        raise ValueError('level must be >= 0')
     if package:
         if not hasattr(package, 'rindex'):
             raise ValueError("__package__ not set to a string")
@@ -943,13 +935,12 @@ def _sanity_check(name, package, level):
         raise ValueError("Empty module name")
 
 
-def _find_search_path(name, import_):
-    """Find the search path for a module.
+_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]
 
-    import_ is expected to be a callable which takes the name of a module to
-    import. It is required to decouple the function from importlib.
+_ERR_MSG = 'No module named {!r}'
 
-    """
+def _find_and_load(name, import_):
+    """Find and load the module."""
     path = None
     parent = name.rpartition('.')[0]
     if parent:
@@ -962,13 +953,28 @@ def _find_search_path(name, import_):
         except AttributeError:
             msg = (_ERR_MSG + '; {} is not a package').format(name, parent)
             raise ImportError(msg)
-    return parent, path
-
-
-
-_IMPLICIT_META_PATH = [BuiltinImporter, FrozenImporter, _DefaultPathFinder]
+    loader = _find_module(name, path)
+    if loader is None:
+        raise ImportError(_ERR_MSG.format(name))
+    elif name not in sys.modules:
+        # The parent import may have already imported this module.
+        loader.load_module(name)
+    # Backwards-compatibility; be nicer to skip the dict lookup.
+    module = sys.modules[name]
+    if parent:
+        # Set the module as an attribute on its parent.
+        parent_module = sys.modules[parent]
+        setattr(parent_module, name.rpartition('.')[2], module)
+    # Set __package__ if the loader did not.
+    if not hasattr(module, '__package__') or module.__package__ is None:
+        try:
+            module.__package__ = module.__name__
+            if not hasattr(module, '__path__'):
+                module.__package__ = module.__package__.rpartition('.')[0]
+        except AttributeError:
+            pass
+    return module
 
-_ERR_MSG = 'No module named {!r}'
 
 def _gcd_import(name, package=None, level=0):
     """Import and return the module based on its name, the package the call is
@@ -991,24 +997,8 @@ def _gcd_import(name, package=None, level=0):
                 raise ImportError(message)
             return module
         except KeyError:
-            pass
-        parent, path = _find_search_path(name, _gcd_import)
-        loader = _find_module(name, path)
-        if loader is None:
-            raise ImportError(_ERR_MSG.format(name))
-        elif name not in sys.modules:
-            # The parent import may have already imported this module.
-            loader.load_module(name)
-        # Backwards-compatibility; be nicer to skip the dict lookup.
-        module = sys.modules[name]
-        if parent:
-            # Set the module as an attribute on its parent.
-            parent_module = sys.modules[parent]
-            setattr(parent_module, name.rpartition('.')[2], module)
-        # Set __package__ if the loader did not.
-        if not hasattr(module, '__package__') or module.__package__ is None:
-            _set___package__(module)
-        return module
+            pass  # Don't want to chain the exception
+        return _find_and_load(name, _gcd_import)
 
 
 def _return_module(module, name, fromlist, level, import_):
@@ -1071,12 +1061,8 @@ def __import__(name, globals={}, locals={}, fromlist=[], level=0):
     import (e.g. ``from ..pkg import mod`` would have a 'level' of 2).
 
     """
-    if not hasattr(name, 'rpartition'):
-        raise TypeError("module name must be str, not {}".format(type(name)))
     if level == 0:
         module = _gcd_import(name)
-    elif level < 0:
-        raise ValueError('level must be >= 0')
     else:
         package = _calc___package__(globals)
         module = _gcd_import(name, package, level)