Add importlib.machinery with its first tenants, BuitinImporter and

FrozenImporter. Docs forthcoming.

I plan on all finders and loaders (and most likely hooks) to live
in imoprtlib.machinery. Utility stuff will end up in importlib.util.
Higher-level API stuff will stay on imoprtlib directly (e.g. import_module).

Lib/importlib/NOTES

 to do
 /////
 
+* Document:
+
+    + The terms "importer", "finder", and "loader".
+    + machinery.BuiltinImporter.
+    + machinery.FrozenImporter.
+
 * Expose resolve_name().
 
 * Backport to Python 2.7.
+
     + import_module
     + resolve_name
 
@@ -11,9 +18,11 @@ to do
   that various implementations can just subclass as needed.
 
 * Expose built-in and frozen importers.
+
     + Make staticmethods so that class can be used directly.
 
 * Reorganize support code.
+
     + Separate general support code and importer-specific (e.g. source) support
       code.
         - Create support modules for each subdirectory (as needed).
@@ -22,12 +31,14 @@ to do
         - Use in source/test_load_module_mixed.
 
 * API simplification?
+
     + read_source -> get_data/source_path
     + read_bytecode -> get_data/bytecode_path
     + write_bytecode -> complete set of bytes for bytecode instead of
       individual arguments.
 
 * Implement PEP 302 protocol for loaders (should just be a matter of testing).
+
     + Built-in.
     + Frozen.
     + Extension.
@@ -36,39 +47,59 @@ to do
 * Create meta_path importer for sys.path.
 
 * OPTIMIZE!
+
   + Write benchmark suite.
   + Fast path common cases.
+
     - Absolute name from sys.path.
     - Relative name from sys.path.
 
 * Public API to expose (w/ docs!)
+
   + abc
+
       - Finder
+
         * find_module
+
       - Loader
+
         * load_module
+
       - ResourceLoader(Loader)
+
         * get_data
+
       - InspectLoader(Loader)
+
         * is_package
         * get_code
         * get_source
+
       - (?) SourceLoader(ResourceLoader)
+
         * source_path
         * bytecode_path
         * write_bytecode
+
   + util
+
       - get_module decorator (new name)
       - check_name decorator (new name)
-  + hooks (?)
+
+  + machinery
+
       - (?) Chained path hook/finder
       - BuiltinImporter
       - FrozenImporter
       - (?) FileFinder
       - Extensions importers
+
           * ExtensionFinder
           * (?) Loader
+
       - Source/bytecode importers
+
           * SourceFinder
           * (?) Loader
 

Lib/importlib/_bootstrap.py

@@ -90,60 +90,17 @@ class closing:
         self.obj.close()
 
 
-class _BuiltinFrozenBaseLoader(object):
+class BuiltinImporter:
 
-    """Base class for meta_path loaders for built-in and frozen modules.
+    """Meta path loader for built-in modules.
 
-    Subclasses must implement:
-
-        * _find(fullname:str) -> bool
-            Finder which returns whether the class can handle the module.
-
-        * _load(fullname:str) -> module
-            Loader which returns the loaded module. The check for sys.modules
-            does not need to be handled by this method.
-
-        * type_:str
-            Name of the type of module being handled. Used in error messages.
+    All methods are either class or static methods, allowing direct use of the
+    class.
 
     """
 
-    def find_module(self, fullname, path=None):
-        """Find a module."""
-        if not self._find(fullname):
-            return None
-        return self
-
-    def load_module(self, fullname):
-        """Load a module."""
-        try:
-            return sys.modules[fullname]
-        except KeyError:
-            pass
-        mod = self._load(fullname)
-        if not mod:
-            raise ImportError("expected {0} module not "
-                                "loaded".format(self.type_))
-        return mod
-
-
-class BuiltinImporter(_BuiltinFrozenBaseLoader):
-
-    """Meta path loader for built-in modules."""
-
-    type_ = "built-in"
-
-    def __init__(self):
-        """Set the methods needed by the class.
-
-        Cannot be set at the class level because the imp module is not
-        necessarily injected until after the class is created.
-
-        """
-        self._find = imp.is_builtin
-        self._load = imp.init_builtin
-
-    def find_module(self, fullname, path=None):
+    @classmethod
+    def find_module(cls, fullname, path=None):
         """Try to find the built-in module.
 
         If 'path' is ever specified then the search is considered a failure.
@@ -151,36 +108,36 @@ class BuiltinImporter(_BuiltinFrozenBaseLoader):
         """
         if path is not None:
             return None
-        return super().find_module(fullname, path)
+        return cls if imp.is_builtin(fullname) else None
 
-    def load_module(self, fullname):
+    @staticmethod
+    def load_module(fullname):
         """Load a built-in module."""
         if fullname not in sys.builtin_module_names:
             raise ImportError("{0} is not a built-in module".format(fullname))
-        return super().load_module(fullname)
-
+        return imp.init_builtin(fullname)
 
-class FrozenImporter(_BuiltinFrozenBaseLoader):
 
-    """Meta path class for importing frozen modules."""
+class FrozenImporter:
 
-    type_ = 'frozen'
+    """Meta path class for importing frozen modules.
 
-    def __init__(self):
-        """Specify the methods needed by the superclass.
+    All methods are either class or static method to allow direct use of the
+    class.
 
-        Because imp may not be injected until after class creation these
-        methods cannot be set at the class level.
+    """
 
-        """
-        self._find = imp.is_frozen
-        self._load = imp.init_frozen
+    @classmethod
+    def find_module(cls, fullname, path=None):
+        """Find a frozen module."""
+        return cls if imp.is_frozen(fullname) else None
 
-    def load_module(self, fullname):
+    @classmethod
+    def load_module(cls, fullname):
         """Load a frozen module."""
-        if not self.find_module(fullname):
+        if cls.find_module(fullname) is None:
             raise ImportError("{0} is not a frozen module".format(fullname))
-        return super().load_module(fullname)
+        return imp.init_frozen(fullname)
 
 
 class ChainedImporter(object):
@@ -707,7 +664,7 @@ class Import(object):
         """Store a default path hook entry and a sequence to internally extend
         sys.meta_path by (passing in None uses default importers)."""
         if extended_meta_path is None:
-            self.extended_meta_path = BuiltinImporter(), FrozenImporter()
+            self.extended_meta_path = BuiltinImporter, FrozenImporter
         else:
             self.extended_meta_path = extended_meta_path
         self.default_path_hook = default_path_hook

Lib/importlib/machinery.py

+"""The machinery of importlib: finders, loaders, hooks, etc."""
+
+from ._bootstrap import BuiltinImporter
+from ._bootstrap import FrozenImporter

Lib/importlib/test/builtin/test_finder.py

-import importlib
+from importlib import machinery
 from .. import support
 
 import sys
@@ -12,7 +12,7 @@ class FinderTests(unittest.TestCase):
     name = 'errno'
 
     find_module = staticmethod(lambda name, path=None:
-                    importlib.BuiltinImporter().find_module(name, path))
+                    machinery.BuiltinImporter.find_module(name, path))
 
 
     def test_find_module(self):

Lib/importlib/test/builtin/test_loader.py

 import importlib
+from importlib import machinery
 from .. import support
 
 import sys
@@ -23,7 +24,7 @@ class LoaderTests(unittest.TestCase):
         self.assert_(module.__name__ in sys.modules)
 
     load_module = staticmethod(lambda name:
-                                importlib.BuiltinImporter().load_module(name))
+                                machinery.BuiltinImporter.load_module(name))
 
     def test_load_module(self):
         # Common case.

Lib/importlib/test/frozen/test_finder.py

-import importlib
+from importlib import machinery
 from ..builtin import test_finder
 from .. import support
 
@@ -10,7 +10,7 @@ class FinderTests(test_finder.FinderTests):
     """Test finding frozen modules."""
 
     def find(self, name, path=None):
-        finder = importlib.FrozenImporter()
+        finder = machinery.FrozenImporter
         return finder.find_module(name, path)
 
 

Lib/importlib/test/frozen/test_loader.py

-import importlib
+from importlib import machinery
 from ..builtin import test_loader
 
 
@@ -6,7 +6,7 @@ class LoaderTests(test_loader.LoaderTests):
 
     name = '__phello__'
     load_module = staticmethod(lambda name:
-                                importlib.FrozenImporter().load_module(name))
+                                machinery.FrozenImporter.load_module(name))
     verification = {'__name__': '__phello__', '__file__': '<frozen>',
                     '__package__': None, '__path__': ['__phello__']}