Issue #20383: Introduce importlib.util.module_from_spec().

Along the way, dismantle importlib._bootstrap._SpecMethods as it was
no longer relevant and constructing the new function required
partially dismantling the class anyway.

Doc/library/importlib.rst

@@ -1129,6 +1129,21 @@ an :term:`importer`.
 
    .. versionadded:: 3.4
 
+.. function:: module_from_spec(spec)
+
+   Create a new module based on **spec**.
+
+   If the module object is from ``spec.loader.create_module()``, then any
+   pre-existing attributes will not be reset. Also, no :exc:`AttributeError`
+   will be raised if triggered while accessing **spec** or setting an attribute
+   on the module.
+
+   This function is preferred over using :class:`types.ModuleType` to create a
+   new module as **spec** is used to set as many import-controlled attributes on
+   the module as possible.
+
+   .. versionadded:: 3.5
+
 .. decorator:: module_for_loader
 
     A :term:`decorator` for :meth:`importlib.abc.Loader.load_module`

Doc/library/types.rst

@@ -115,6 +115,10 @@ Standard names are defined for the following types:
    The type of :term:`modules <module>`. Constructor takes the name of the
    module to be created and optionally its :term:`docstring`.
 
+   .. note::
+      Use :func:`importlib.util.module_from_spec` to create a new module if you
+      wish to set the various import-controlled attributes.
+
    .. attribute:: __doc__
 
       The :term:`docstring` of the module. Defaults to ``None``.

Doc/whatsnew/3.5.rst

@@ -153,6 +153,10 @@ importlib
   With a module object that you want to initialize you can then use
   ``exec(code, module.__dict__)`` to execute the code in the module.
 
+* :func:`importlib.util.module_from_spec` is now the preferred way to create a
+  new module. Compared to :class:`types.ModuleType`, this new function will set
+  the various import-controlled attributes based on the passed-in spec object.
+
 inspect
 -------
 

Lib/imp.py

@@ -16,7 +16,7 @@ except ImportError:
     # Platform doesn't support dynamic loading.
     load_dynamic = None
 
-from importlib._bootstrap import SourcelessFileLoader, _ERR_MSG, _SpecMethods
+from importlib._bootstrap import SourcelessFileLoader, _ERR_MSG, _exec, _load
 
 from importlib import machinery
 from importlib import util
@@ -164,11 +164,10 @@ class _LoadSourceCompatibility(_HackedGetData, machinery.SourceFileLoader):
 def load_source(name, pathname, file=None):
     loader = _LoadSourceCompatibility(name, pathname, file)
     spec = util.spec_from_file_location(name, pathname, loader=loader)
-    methods = _SpecMethods(spec)
     if name in sys.modules:
-        module = methods.exec(sys.modules[name])
+        module = _exec(spec, sys.modules[name])
     else:
-        module = methods.load()
+        module = _load(spec)
     # To allow reloading to potentially work, use a non-hacked loader which
     # won't rely on a now-closed file object.
     module.__loader__ = machinery.SourceFileLoader(name, pathname)
@@ -185,11 +184,10 @@ def load_compiled(name, pathname, file=None):
     """**DEPRECATED**"""
     loader = _LoadCompiledCompatibility(name, pathname, file)
     spec = util.spec_from_file_location(name, pathname, loader=loader)
-    methods = _SpecMethods(spec)
     if name in sys.modules:
-        module = methods.exec(sys.modules[name])
+        module = _exec(spec, sys.modules[name])
     else:
-        module = methods.load()
+        module = _load(spec)
     # To allow reloading to potentially work, use a non-hacked loader which
     # won't rely on a now-closed file object.
     module.__loader__ = SourcelessFileLoader(name, pathname)
@@ -210,11 +208,10 @@ def load_package(name, path):
             raise ValueError('{!r} is not a package'.format(path))
     spec = util.spec_from_file_location(name, path,
                                         submodule_search_locations=[])
-    methods = _SpecMethods(spec)
     if name in sys.modules:
-        return methods.exec(sys.modules[name])
+        return _exec(spec, sys.modules[name])
     else:
-        return methods.load()
+        return _load(spec)
 
 
 def load_module(name, file, filename, details):

Lib/importlib/__init__.py

@@ -145,8 +145,7 @@ def reload(module):
             pkgpath = None
         target = module
         spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
-        methods = _bootstrap._SpecMethods(spec)
-        methods.exec(module)
+        _bootstrap._exec(spec, module)
         # The module may have replaced itself in sys.modules!
         return sys.modules[name]
     finally:

Lib/importlib/abc.py

@@ -126,7 +126,7 @@ class Loader(metaclass=abc.ABCMeta):
         create_module() is optional.
 
         """
-        # By default, defer to _SpecMethods.create() for the new module.
+        # By default, defer to default semantics for the new module.
         return None
 
     # We don't define exec_module() here since that would break

Lib/importlib/util.py

@@ -3,6 +3,7 @@ from . import abc
 from ._bootstrap import MAGIC_NUMBER
 from ._bootstrap import cache_from_source
 from ._bootstrap import decode_source
+from ._bootstrap import module_from_spec
 from ._bootstrap import source_from_cache
 from ._bootstrap import spec_from_loader
 from ._bootstrap import spec_from_file_location

Lib/pkgutil.py

@@ -616,7 +616,7 @@ def get_data(package, resource):
         return None
     # XXX needs test
     mod = (sys.modules.get(package) or
-           importlib._bootstrap._SpecMethods(spec).load())
+           importlib._bootstrap._load(spec))
     if mod is None or not hasattr(mod, '__file__'):
         return None
 

Lib/pydoc.py

@@ -263,9 +263,8 @@ def synopsis(filename, cache={}):
             # XXX We probably don't need to pass in the loader here.
             spec = importlib.util.spec_from_file_location('__temp__', filename,
                                                           loader=loader)
-            _spec = importlib._bootstrap._SpecMethods(spec)
             try:
-                module = _spec.load()
+                module = importlib._bootstrap._load(spec)
             except:
                 return None
             del sys.modules['__temp__']
@@ -297,9 +296,8 @@ def importfile(path):
         loader = importlib._bootstrap.SourceFileLoader(name, path)
     # XXX We probably don't need to pass in the loader here.
     spec = importlib.util.spec_from_file_location(name, path, loader=loader)
-    _spec = importlib._bootstrap._SpecMethods(spec)
     try:
-        return _spec.load()
+        return importlib._bootstrap._load(spec)
     except:
         raise ErrorDuringImport(path, sys.exc_info())
 
@@ -2057,9 +2055,8 @@ class ModuleScanner:
                     else:
                         path = None
                 else:
-                    _spec = importlib._bootstrap._SpecMethods(spec)
                     try:
-                        module = _spec.load()
+                        module = importlib._bootstrap._load(spec)
                     except ImportError:
                         if onerror:
                             onerror(modname)

Lib/runpy.py

@@ -58,7 +58,7 @@ class _ModifiedArgv0(object):
         self.value = self._sentinel
         sys.argv[0] = self._saved_value
 
-# TODO: Replace these helpers with importlib._bootstrap._SpecMethods
+# TODO: Replace these helpers with importlib._bootstrap functions
 def _run_code(code, run_globals, init_globals=None,
               mod_name=None, mod_spec=None,
               pkg_name=None, script_name=None):

Lib/test/test_tools.py

@@ -407,7 +407,7 @@ class PdepsTests(unittest.TestCase):
     def setUpClass(self):
         path = os.path.join(scriptsdir, 'pdeps.py')
         spec = importlib.util.spec_from_file_location('pdeps', path)
-        self.pdeps = importlib._bootstrap._SpecMethods(spec).load()
+        self.pdeps = importlib._bootstrap._load(spec)
 
     @classmethod
     def tearDownClass(self):
@@ -432,7 +432,7 @@ class Gprof2htmlTests(unittest.TestCase):
     def setUp(self):
         path = os.path.join(scriptsdir, 'gprof2html.py')
         spec = importlib.util.spec_from_file_location('gprof2html', path)
-        self.gprof = importlib._bootstrap._SpecMethods(spec).load()
+        self.gprof = importlib._bootstrap._load(spec)
         oldargv = sys.argv
         def fixup():
             sys.argv = oldargv

Misc/NEWS

@@ -89,6 +89,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #20383: Introduce importlib.util.module_from_spec() as the preferred way
+  to create a new module.
+
 - Issue #21552: Fixed possible integer overflow of too long string lengths in
   the tkinter module on 64-bit platforms.
 

setup.py

@@ -342,7 +342,7 @@ class PyBuildExt(build_ext):
         spec = importlib.util.spec_from_file_location(ext.name, ext_filename,
                                                       loader=loader)
         try:
-            importlib._bootstrap._SpecMethods(spec).load()
+            importlib._bootstrap._load(spec)
         except ImportError as why:
             self.failed_on_import.append(ext.name)
             self.announce('*** WARNING: renaming "%s" since importing it'