[Python-checkins] bpo-42133: update parts of the stdlib to fall back to `__spec__.loader` when `__loader__` is missing (#22929)

[brettcannon]

https://github.com/python/cpython/commit/825ac383327255d38b69a753e5e41710bb3ed010
commit: 825ac383327255d38b69a753e5e41710bb3ed010
branch: master
author: Brett Cannon <brett at python.org>
committer: brettcannon <brett at python.org>
date: 2020-11-06T18:45:56-08:00
summary:

bpo-42133: update parts of the stdlib to fall back to `__spec__.loader` when `__loader__` is missing (#22929)

files:
A Misc/NEWS.d/next/Library/2020-10-23-15-47-47.bpo-42133.BzizYV.rst
M Doc/whatsnew/3.10.rst
M Lib/doctest.py
M Lib/inspect.py
M Lib/linecache.py
M Lib/site.py

diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index 1e6c7c4067f3f..a735bf235435c 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -186,6 +186,12 @@ by :func:`curses.color_content`, :func:`curses.init_color`,
 support is provided by the underlying ncurses library.
 (Contributed by Jeffrey Kintscher and Hans Petter Jansson in :issue:`36982`.)
 
+doctest
+-------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 encodings
 ---------
 :func:`encodings.normalize_encoding` now ignores non-ASCII characters.
@@ -198,6 +204,18 @@ Added the *root_dir* and *dir_fd* parameters in :func:`~glob.glob` and
 :func:`~glob.iglob` which allow to specify the root directory for searching.
 (Contributed by Serhiy Storchaka in :issue:`38144`.)
 
+inspect
+-------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
+linecache
+---------
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 os
 --
 
@@ -217,6 +235,12 @@ The :mod:`shelve` module now uses :data:`pickle.DEFAULT_PROTOCOL` by default
 instead of :mod:`pickle` protocol ``3`` when creating shelves.
 (Contributed by Zackery Spytz in :issue:`34204`.)
 
+site
+----
+
+When a module does not define ``__loader__``, fall back to ``__spec__.loader``.
+(Contributed by Brett Cannon in :issue:`42133`.)
+
 sys
 ---
 
diff --git a/Lib/doctest.py b/Lib/doctest.py
index baa503c83f875..5bb35c9715d1e 100644
--- a/Lib/doctest.py
+++ b/Lib/doctest.py
@@ -222,13 +222,17 @@ def _load_testfile(filename, package, module_relative, encoding):
     if module_relative:
         package = _normalize_module(package, 3)
         filename = _module_relative_path(package, filename)
-        if getattr(package, '__loader__', None) is not None:
-            if hasattr(package.__loader__, 'get_data'):
-                file_contents = package.__loader__.get_data(filename)
-                file_contents = file_contents.decode(encoding)
-                # get_data() opens files as 'rb', so one must do the equivalent
-                # conversion as universal newlines would do.
-                return _newline_convert(file_contents), filename
+        if (loader := getattr(package, '__loader__', None)) is None:
+            try:
+                loader = package.__spec__.loader
+            except AttributeError:
+                pass
+        if hasattr(loader, 'get_data'):
+            file_contents = loader.get_data(filename)
+            file_contents = file_contents.decode(encoding)
+            # get_data() opens files as 'rb', so one must do the equivalent
+            # conversion as universal newlines would do.
+            return _newline_convert(file_contents), filename
     with open(filename, encoding=encoding) as f:
         return f.read(), filename
 
diff --git a/Lib/inspect.py b/Lib/inspect.py
index ac127cbd725b9..7412d0e837cf1 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -707,10 +707,13 @@ def getsourcefile(object):
     if os.path.exists(filename):
         return filename
     # only return a non-existent filename if the module has a PEP 302 loader
-    if getattr(getmodule(object, filename), '__loader__', None) is not None:
+    module = getmodule(object, filename)
+    if getattr(module, '__loader__', None) is not None:
+        return filename
+    elif getattr(getattr(module, "__spec__", None), "loader", None) is not None:
         return filename
     # or it is in the linecache
-    if filename in linecache.cache:
+    elif filename in linecache.cache:
         return filename
 
 def getabsfile(object, _filename=None):
diff --git a/Lib/linecache.py b/Lib/linecache.py
index fa5dbd09eab86..513b17e999880 100644
--- a/Lib/linecache.py
+++ b/Lib/linecache.py
@@ -165,9 +165,14 @@ def lazycache(filename, module_globals):
     if not filename or (filename.startswith('<') and filename.endswith('>')):
         return False
     # Try for a __loader__, if available
-    if module_globals and '__loader__' in module_globals:
-        name = module_globals.get('__name__')
-        loader = module_globals['__loader__']
+    if module_globals and '__name__' in module_globals:
+        name = module_globals['__name__']
+        if (loader := module_globals.get('__loader__')) is None:
+            if spec := module_globals.get('__spec__'):
+                try:
+                    loader = spec.loader
+                except AttributeError:
+                    pass
         get_source = getattr(loader, 'get_source', None)
 
         if name and get_source:
diff --git a/Lib/site.py b/Lib/site.py
index 4d3b869fff77a..3a0f619d71c86 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -105,8 +105,15 @@ def makepath(*paths):
 def abs_paths():
     """Set all module __file__ and __cached__ attributes to an absolute path"""
     for m in set(sys.modules.values()):
-        if (getattr(getattr(m, '__loader__', None), '__module__', None) not in
-                ('_frozen_importlib', '_frozen_importlib_external')):
+        loader_module = None
+        try:
+            loader_module = m.__loader__.__module__
+        except AttributeError:
+            try:
+                loader_module = m.__spec__.loader.__module__
+            except AttributeError:
+                pass
+        if loader_module not in {'_frozen_importlib', '_frozen_importlib_external'}:
             continue   # don't mess with a PEP 302-supplied __file__
         try:
             m.__file__ = os.path.abspath(m.__file__)
diff --git a/Misc/NEWS.d/next/Library/2020-10-23-15-47-47.bpo-42133.BzizYV.rst b/Misc/NEWS.d/next/Library/2020-10-23-15-47-47.bpo-42133.BzizYV.rst
new file mode 100644
index 0000000000000..f3cfa1a8dce33
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-10-23-15-47-47.bpo-42133.BzizYV.rst
@@ -0,0 +1,2 @@
+Update various modules in the stdlib to fall back on `__spec__.loader` when
+`__loader__` isn't defined on a module.