Rewrite the code implementing __import__ for importlib. Now it is much simpler

and relies much more on meta path finders to abstract out various parts of
import.

As part of this the semantics for import_module tightened up and now follow
__import__ much more closely (biggest thing is that the 'package' argument must
now already be imported, else a SystemError is raised).

Doc/library/importlib.rst

@@ -72,11 +72,15 @@ Functions
     import in absolute or relative terms
     (e.g. either ``pkg.mod`` or ``..mod``). If the name is
     specified in relative terms, then the *package* argument must be
-    specified to the package which is to act as the anchor for resolving the
+    set to the package which is to act as the anchor for resolving the
     package name (e.g. ``import_module('..mod', 'pkg.subpkg')`` will import
-    ``pkg.mod``). The specified module will be inserted into
-    :data:`sys.modules` and returned.
+    ``pkg.mod``).
 
+    The :func:`import_module` function acts as a simplifying wrapper around
+    :func:`__import__`. This means all semantics of the function are derived
+    from :func:`__import__`, including requiring the package where an import is
+    occuring from to already be imported (i.e., *package* must already be
+    imported).
 
 :mod:`importlib.machinery` -- Importers and path hooks
 ------------------------------------------------------

Lib/importlib/NOTES

 to do
 /////
 
-* Create sandbox directory for a distutils packaging of what is in Python 2.7.
-
 * Use rpartition for getting the package of a module.
 
-    + Make sure that an empty string is acceptable for __package__.
-
-* Create meta_path importer for sys.path.
-
-    + Document.
-
-* Refactor __import__.
-
-    + Create a greatest common denominator function for __import__/import_module
-      that takes in an absolute module name and performs the import.
-
-      - Needs of __import__
-
-        * Figure out caller's package.
-        * Import module.
-        * Set __package__.
-        * Figure out what module to return.
-
-      - Needs of import_module
-
-        * Resolve name/level.
-        * Import module.
-
-    + Use GCD import for __import__.
-    + Use GCD import for import_module.
+    + Make sure there is a test for the empty string as acceptable for
+      __package__.
 
 * Implement PEP 302 protocol for loaders (should just be a matter of testing).
 
@@ -66,13 +41,11 @@ to do
 
         * source_path
         * bytecode_path
-        * write_bytecode
+        * write_bytecode (not abstract)
 
   + util
 
-      - get_module decorator (new name)
-      - check_name decorator (new name)
-      - resolve_name
+      - get_module decorator (rename: module_for_loader)
 
   + machinery
 
@@ -88,6 +61,8 @@ to do
           * SourceFinder
           * (?) Loader
 
+      - PathFinder
+
 * Write benchmark suite.
 
 * OPTIMIZE!

Lib/importlib/__init__.py

@@ -29,7 +29,7 @@ def _set__import__():
     """Set __import__ to an instance of Import."""
     global original__import__
     original__import__ = __import__
-    __builtins__['__import__'] = Import()
+    __builtins__['__import__'] = _bootstrap._import
 
 
 def _reset__import__():
@@ -114,7 +114,7 @@ marshal._r_long = _r_long
 
 # Public API #########################################################
 
-__import__ = _bootstrap.Import().__call__
+__import__ = _bootstrap._import
 
 
 def import_module(name, package=None):
@@ -125,17 +125,15 @@ def import_module(name, package=None):
     relative import to an absolute import.
 
     """
+    level = 0
     if name.startswith('.'):
         if not package:
             raise TypeError("relative imports require the 'package' argument")
-        level = 0
         for character in name:
             if character != '.':
                 break
             level += 1
-        name = Import._resolve_name(name[level:], package, level)
-    __import__(name)
-    return sys.modules[name]
+    return _bootstrap._gcd_import(name[level:], package, level)
 
 
 # XXX This should go away once the public API is done.

Lib/importlib/test/import_/test___package__.py

@@ -38,8 +38,9 @@ class Using__package__(unittest.TestCase):
         with util.mock_modules('pkg.__init__', 'pkg.fake') as importer:
             with util.import_state(meta_path=[importer]):
                 import_util.import_('pkg.fake')
-                module = import_util.import_('', globals={'__package__': 'pkg.fake'},
-                                 fromlist=['attr'], level=2)
+                module = import_util.import_('',
+                                            globals={'__package__': 'pkg.fake'},
+                                            fromlist=['attr'], level=2)
         self.assertEquals(module.__name__, 'pkg')
 
     def test_using___name__(self):
@@ -82,7 +83,7 @@ class Setting__package__(unittest.TestCase):
             with util.import_state(meta_path=[mock]):
                 del mock['top_level'].__package__
                 module = import_util.import_('top_level')
-                self.assert_(module.__package__ is None)
+                self.assertEqual(module.__package__, '')
 
     # [package]
     def test_package(self):

Lib/importlib/test/import_/test_caching.py

@@ -64,7 +64,8 @@ class UseCache(unittest.TestCase):
             with util.import_state(meta_path=[importer]):
                 module = import_util.import_('pkg', fromlist=['module'])
                 self.assert_(hasattr(module, 'module'))
-                self.assertEquals(id(module.module), id(sys.modules['pkg.module']))
+                self.assertEquals(id(module.module),
+                                  id(sys.modules['pkg.module']))
 
 
 def test_main():

Lib/importlib/test/import_/test_path.py

@@ -10,148 +10,6 @@ from types import MethodType
 import unittest
 
 
-class BaseTests(unittest.TestCase):
-
-    """When sys.meta_path cannot find the desired module, sys.path is
-    consulted. For each entry on the sequence [order], sys.path_importer_cache
-    is checked to see if it contains a key for the entry [cache check]. If an
-    importer is found then it is consulted before trying the next entry in
-    sys.path [cache use]. The 'path' argument to find_module() is never used
-    when trying to find a module [path not used].
-
-    If an entry from sys.path is not in sys.path_importer_cache, sys.path_hooks
-    is called in turn [hooks order]. If a path hook cannot handle an entry,
-    ImportError is raised [hook failure]. Otherwise the resulting object is
-    cached in sys.path_importer_cache and then consulted [hook success]. If no
-    hook is found, None is set in sys.path_importer_cache and the default
-    importer is tried [no hook].
-
-    For use of __path__ in a package, the above is all true, just substitute
-    "sys.path" for "__path__".
-
-    """
-
-    def order_test(self, to_import, entry, search_path, path=[]):
-        # [order]
-        log = []
-        class LogFindModule(util.mock_modules):
-            def find_module(self, fullname):
-                log.append(self)
-                return super().find_module(fullname)
-
-        assert len(search_path) == 2
-        misser = LogFindModule(search_path[0])
-        hitter = LogFindModule(to_import)
-        with nested(misser, hitter):
-            cache = dict(zip(search_path, (misser, hitter)))
-            with util.import_state(path=path, path_importer_cache=cache):
-                import_util.import_(to_import)
-        self.assertEquals(log[0], misser)
-        self.assertEquals(log[1], hitter)
-
-    @import_util.importlib_only  # __import__ uses PyDict_GetItem(), bypassing log.
-    def cache_use_test(self, to_import, entry, path=[]):
-        # [cache check], [cache use]
-        log = []
-        class LoggingDict(dict):
-            def __getitem__(self, item):
-                log.append(item)
-                return super(LoggingDict, self).__getitem__(item)
-
-        with util.mock_modules(to_import) as importer:
-            cache = LoggingDict()
-            cache[entry] = importer
-            with util.import_state(path=[entry], path_importer_cache=cache):
-                module = import_util.import_(to_import, fromlist=['a'])
-            self.assert_(module is importer[to_import])
-        self.assertEquals(len(cache), 1)
-        self.assertEquals([entry], log)
-
-    def hooks_order_test(self, to_import, entry, path=[]):
-        # [hooks order], [hooks failure], [hook success]
-        log = []
-        def logging_hook(entry):
-            log.append(entry)
-            raise ImportError
-        with util.mock_modules(to_import) as importer:
-            hitter = import_util.mock_path_hook(entry, importer=importer)
-            path_hooks = [logging_hook, logging_hook, hitter]
-            with util.import_state(path_hooks=path_hooks, path=path):
-                import_util.import_(to_import)
-                self.assertEquals(sys.path_importer_cache[entry], importer)
-        self.assertEquals(len(log), 2)
-
-    # [no hook] XXX Worry about after deciding how to handle the default hook.
-
-    def path_argument_test(self, to_import):
-        # [path not used]
-        class BadImporter:
-            """Class to help detect TypeError from calling find_module() with
-            an improper number of arguments."""
-            def find_module(name):
-                raise ImportError
-
-        try:
-            import_util.import_(to_import)
-        except ImportError:
-            pass
-
-
-class PathTests(BaseTests):
-
-    """Tests for sys.path."""
-
-    def test_order(self):
-        self.order_test('hit', 'second', ['first', 'second'],
-                        ['first', 'second'])
-
-    def test_cache_use(self):
-        entry = "found!"
-        self.cache_use_test('hit', entry, [entry])
-
-    def test_hooks_order(self):
-        entry = "found!"
-        self.hooks_order_test('hit', entry, [entry])
-
-    def test_path_argument(self):
-        name = 'total junk'
-        with util.uncache(name):
-            self.path_argument_test(name)
-
-
-class __path__Tests(BaseTests):
-
-    """Tests for __path__."""
-
-    def run_test(self, test, entry, path, *args):
-        with util.mock_modules('pkg.__init__') as importer:
-            importer['pkg'].__path__ = path
-            importer.load_module('pkg')
-            test('pkg.hit', entry, *args)
-
-
-    @import_util.importlib_only  # XXX Unknown reason why this fails.
-    def test_order(self):
-        self.run_test(self.order_test, 'second', ('first', 'second'), ['first',
-            'second'])
-
-    def test_cache_use(self):
-        location = "I'm here!"
-        self.run_test(self.cache_use_test, location, [location])
-
-    def test_hooks_order(self):
-        location = "I'm here!"
-        self.run_test(self.hooks_order_test, location, [location])
-
-    def test_path_argument(self):
-        module = imp.new_module('pkg')
-        module.__path__ = ['random __path__']
-        name = 'pkg.whatever'
-        sys.modules['pkg'] = module
-        with util.uncache('pkg', name):
-            self.path_argument_test(name)
-
-
 class FinderTests(unittest.TestCase):
 
     """Tests for SysPathImporter."""

Lib/importlib/test/import_/util.py

 import functools
-import importlib
+import importlib._bootstrap
 
 
 using___import__ = False
@@ -9,7 +9,8 @@ def import_(*args, **kwargs):
     """Delegate to allow for injecting different implementations of import."""
     if using___import__:
         return __import__(*args, **kwargs)
-    return importlib.Import()(*args, **kwargs)
+    #return importlib.Import()(*args, **kwargs)
+    return importlib._bootstrap._import(*args, **kwargs)
 
 
 def importlib_only(fxn):

Lib/importlib/test/test_api.py

-import unittest
-import importlib
 from . import util
+import imp
+import importlib
+import sys
+import unittest
 
 
 class ImportModuleTests(unittest.TestCase):
@@ -33,6 +35,7 @@ class ImportModuleTests(unittest.TestCase):
         relative_name = '.{0}'.format(module_name)
         with util.mock_modules(pkg_long_name, absolute_name) as mock:
             with util.import_state(meta_path=[mock]):
+                importlib.import_module(pkg_name)
                 module = importlib.import_module(relative_name, pkg_name)
                 self.assertEqual(module.__name__, absolute_name)
 
@@ -44,6 +47,7 @@ class ImportModuleTests(unittest.TestCase):
         name = '{0}.mod'.format(pkg_name)
         with util.mock_modules(pkg_long_name, name) as mock:
             with util.import_state(meta_path=[mock]):
+                importlib.import_module(pkg_name)
                 module = importlib.import_module(name, pkg_name)
                 self.assertEqual(module.__name__, name)