gh-65961: Do not rely solely on __cached__ (GH-97990)

Make sure `__spec__.cached` (at minimum) can be used.

Author: brettcannon

Doc/c-api/import.rst

@@ -150,6 +150,11 @@ Importing Modules
    See also :c:func:`PyImport_ExecCodeModuleEx` and
    :c:func:`PyImport_ExecCodeModuleWithPathnames`.
 
+   .. versionchanged:: 3.12
+      The setting of :attr:`__cached__` and :attr:`__loader__` is
+      deprecated. See :class:`~importlib.machinery.ModuleSpec` for
+      alternatives.
+
 
 .. c:function:: PyObject* PyImport_ExecCodeModuleEx(const char *name, PyObject *co, const char *pathname)
 
@@ -167,6 +172,10 @@ Importing Modules
 
    .. versionadded:: 3.3
 
+   .. versionchanged:: 3.12
+      Setting :attr:`__cached__` is deprecated. See
+      :class:`~importlib.machinery.ModuleSpec` for alternatives.
+
 
 .. c:function:: PyObject* PyImport_ExecCodeModuleWithPathnames(const char *name, PyObject *co, const char *pathname, const char *cpathname)
 

Doc/library/runpy.rst

@@ -93,6 +93,11 @@ The :mod:`runpy` module provides two functions:
       run this way, as well as ensuring the real module name is always
       accessible as ``__spec__.name``.
 
+   .. versionchanged:: 3.12
+      The setting of ``__cached__``, ``__loader__``, and
+      ``__package__`` are deprecated. See
+      :class:`~importlib.machinery.ModuleSpec` for alternatives.
+
 .. function:: run_path(path_name, init_globals=None, run_name=None)
 
    .. index::
@@ -163,6 +168,10 @@ The :mod:`runpy` module provides two functions:
       case where ``__main__`` is imported from a valid sys.path entry rather
       than being executed directly.
 
+   .. versionchanged:: 3.12
+      The setting of ``__cached__``, ``__loader__``, and
+      ``__package__`` are deprecated.
+
 .. seealso::
 
    :pep:`338` -- Executing modules as scripts

Doc/whatsnew/3.12.rst

@@ -280,8 +280,8 @@ Pending Removal in Python 3.14
 * Creating :c:data:`immutable types <Py_TPFLAGS_IMMUTABLETYPE>` with mutable
   bases using the C API.
 
-* ``__package__`` will cease to be set or taken into consideration by
-  the import system (:gh:`97879`).
+* ``__package__`` and ``__cached__`` will cease to be set or taken
+  into consideration by the import system (:gh:`97879`).
 
 
 Pending Removal in Future Versions

Lib/cProfile.py

@@ -7,6 +7,7 @@
 __all__ = ["run", "runctx", "Profile"]
 
 import _lsprof
+import importlib.machinery
 import profile as _pyprofile
 
 # ____________________________________________________________
@@ -169,9 +170,12 @@ def main():
             sys.path.insert(0, os.path.dirname(progname))
             with open(progname, 'rb') as fp:
                 code = compile(fp.read(), progname, 'exec')
+            spec = importlib.machinery.ModuleSpec(name='__main__', loader=None,
+                                                  origin=progname)
             globs = {
-                '__file__': progname,
-                '__name__': '__main__',
+                '__spec__': spec,
+                '__file__': spec.origin,
+                '__name__': spec.name,
                 '__package__': None,
                 '__cached__': None,
             }

Lib/importlib/_bootstrap_external.py

@@ -182,6 +182,16 @@ def _path_isabs(path):
         return path.startswith(path_separators)
 
 
+def _path_abspath(path):
+    """Replacement for os.path.abspath."""
+    if not _path_isabs(path):
+        for sep in path_separators:
+            path = path.removeprefix(f".{sep}")
+        return _path_join(_os.getcwd(), path)
+    else:
+        return path
+
+
 def _write_atomic(path, data, mode=0o666):
     """Best-effort function to write data to a path atomically.
     Be prepared to handle a FileExistsError if concurrent writing of the
@@ -494,8 +504,7 @@ def cache_from_source(path, debug_override=None, *, optimization=None):
         # make it absolute (`C:\Somewhere\Foo\Bar`), then make it root-relative
         # (`Somewhere\Foo\Bar`), so we end up placing the bytecode file in an
         # unambiguous `C:\Bytecode\Somewhere\Foo\Bar\`.
-        if not _path_isabs(head):
-            head = _path_join(_os.getcwd(), head)
+        head = _path_abspath(head)
 
         # Strip initial drive from a Windows path. We know we have an absolute
         # path here, so the second part of the check rules out a POSIX path that
@@ -808,11 +817,10 @@ def spec_from_file_location(name, location=None, *, loader=None,
                 pass
     else:
         location = _os.fspath(location)
-        if not _path_isabs(location):
-            try:
-                location = _path_join(_os.getcwd(), location)
-            except OSError:
-                pass
+        try:
+            location = _path_abspath(location)
+        except OSError:
+            pass
 
     # If the location is on the filesystem, but doesn't actually exist,
     # we could return None here, indicating that the location is not
@@ -1564,10 +1572,8 @@ def __init__(self, path, *loader_details):
         # Base (directory) path
         if not path or path == '.':
             self.path = _os.getcwd()
-        elif not _path_isabs(path):
-            self.path = _path_join(_os.getcwd(), path)
         else:
-            self.path = path
+            self.path = _path_abspath(path)
         self._path_mtime = -1
         self._path_cache = set()
         self._relaxed_path_cache = set()
@@ -1717,6 +1723,8 @@ def _fix_up_module(ns, name, pathname, cpathname=None):
             loader = SourceFileLoader(name, pathname)
     if not spec:
         spec = spec_from_file_location(name, pathname, loader=loader)
+        if cpathname:
+            spec.cached = _path_abspath(cpathname)
     try:
         ns['__spec__'] = spec
         ns['__loader__'] = loader

Lib/inspect.py

@@ -281,30 +281,15 @@ def get_annotations(obj, *, globals=None, locals=None, eval_str=False):
 
 # ----------------------------------------------------------- type-checking
 def ismodule(object):
-    """Return true if the object is a module.
-
-    Module objects provide these attributes:
-        __cached__      pathname to byte compiled file
-        __doc__         documentation string
-        __file__        filename (missing for built-in modules)"""
+    """Return true if the object is a module."""
     return isinstance(object, types.ModuleType)
 
 def isclass(object):
-    """Return true if the object is a class.
-
-    Class objects provide these attributes:
-        __doc__         documentation string
-        __module__      name of module in which this class was defined"""
+    """Return true if the object is a class."""
     return isinstance(object, type)
 
 def ismethod(object):
-    """Return true if the object is an instance method.
-
-    Instance method objects provide these attributes:
-        __doc__         documentation string
-        __name__        name with which this method was defined
-        __func__        function object containing implementation of method
-        __self__        instance to which this method is bound"""
+    """Return true if the object is an instance method."""
     return isinstance(object, types.MethodType)
 
 def ismethoddescriptor(object):

Lib/profile.py

@@ -24,6 +24,7 @@
 # governing permissions and limitations under the License.
 
 
+import importlib.machinery
 import sys
 import time
 import marshal
@@ -589,9 +590,12 @@ def main():
             sys.path.insert(0, os.path.dirname(progname))
             with open(progname, 'rb') as fp:
                 code = compile(fp.read(), progname, 'exec')
+            spec = importlib.machinery.ModuleSpec(name='__main__', loader=None,
+                                                  origin=progname)
             globs = {
-                '__file__': progname,
-                '__name__': '__main__',
+                '__spec__': spec,
+                '__file__': spec.origin,
+                '__name__': spec.name,
                 '__package__': None,
                 '__cached__': None,
             }

Lib/test/test_importlib/import_/test_helpers.py

@@ -0,0 +1,71 @@
+"""Tests for helper functions used by import.c ."""
+
+from importlib import _bootstrap_external, machinery
+import os.path
+import unittest
+
+from .. import util
+
+
+class FixUpModuleTests:
+
+    def test_no_loader_but_spec(self):
+        loader = object()
+        name = "hello"
+        path = "hello.py"
+        spec = machinery.ModuleSpec(name, loader)
+        ns = {"__spec__": spec}
+        _bootstrap_external._fix_up_module(ns, name, path)
+
+        expected = {"__spec__": spec, "__loader__": loader, "__file__": path,
+                    "__cached__": None}
+        self.assertEqual(ns, expected)
+
+    def test_no_loader_no_spec_but_sourceless(self):
+        name = "hello"
+        path = "hello.py"
+        ns = {}
+        _bootstrap_external._fix_up_module(ns, name, path, path)
+
+        expected = {"__file__": path, "__cached__": path}
+
+        for key, val in expected.items():
+            with self.subTest(f"{key}: {val}"):
+                self.assertEqual(ns[key], val)
+
+        spec = ns["__spec__"]
+        self.assertIsInstance(spec, machinery.ModuleSpec)
+        self.assertEqual(spec.name, name)
+        self.assertEqual(spec.origin, os.path.abspath(path))
+        self.assertEqual(spec.cached, os.path.abspath(path))
+        self.assertIsInstance(spec.loader, machinery.SourcelessFileLoader)
+        self.assertEqual(spec.loader.name, name)
+        self.assertEqual(spec.loader.path, path)
+        self.assertEqual(spec.loader, ns["__loader__"])
+
+    def test_no_loader_no_spec_but_source(self):
+        name = "hello"
+        path = "hello.py"
+        ns = {}
+        _bootstrap_external._fix_up_module(ns, name, path)
+
+        expected = {"__file__": path, "__cached__": None}
+
+        for key, val in expected.items():
+            with self.subTest(f"{key}: {val}"):
+                self.assertEqual(ns[key], val)
+
+        spec = ns["__spec__"]
+        self.assertIsInstance(spec, machinery.ModuleSpec)
+        self.assertEqual(spec.name, name)
+        self.assertEqual(spec.origin, os.path.abspath(path))
+        self.assertIsInstance(spec.loader, machinery.SourceFileLoader)
+        self.assertEqual(spec.loader.name, name)
+        self.assertEqual(spec.loader.path, path)
+        self.assertEqual(spec.loader, ns["__loader__"])
+
+
+FrozenFixUpModuleTests, SourceFixUpModuleTests = util.test_both(FixUpModuleTests)
+
+if __name__ == "__main__":
+    unittest.main()

Lib/test/test_inspect.py

@@ -4358,8 +4358,11 @@ def test_details(self):
                                         'unittest', '--details')
         output = out.decode()
         # Just a quick sanity check on the output
+        self.assertIn(module.__spec__.name, output)
         self.assertIn(module.__name__, output)
+        self.assertIn(module.__spec__.origin, output)
         self.assertIn(module.__file__, output)
+        self.assertIn(module.__spec__.cached, output)
         self.assertIn(module.__cached__, output)
         self.assertEqual(err, b'')
 

Lib/test/test_pydoc.py

@@ -702,7 +702,7 @@ def test_synopsis(self):
     def test_synopsis_sourceless(self):
         os = import_helper.import_fresh_module('os')
         expected = os.__doc__.splitlines()[0]
-        filename = os.__cached__
+        filename = os.__spec__.cached
         synopsis = pydoc.synopsis(filename)
 
         self.assertEqual(synopsis, expected)

Misc/NEWS.d/next/Library/2022-10-06-17-59-22.gh-issue-65961.SXlQnI.rst

@@ -0,0 +1,2 @@
+Do not rely solely on ``__cached__`` on modules; code will also support
+``__spec__.cached``.