gh-157955: Support type aliases for inspect source inspection functions

Doc/library/inspect.rst

@@ -750,10 +750,14 @@ Retrieving source code
 .. function:: getcomments(object)
 
    Return in a single string any lines of comments immediately preceding the
-   object's source code (for a class, function, or method), or at the top of the
-   Python source file (if the object is a module).  If the object's source code
-   is unavailable, return ``None``.  This could happen if the object has been
-   defined in C or the interactive shell.
+   object's source code (for a class, function, method, or type alias), or at the
+   top of the Python source file (if the object is a module).  If the object's
+   source code is unavailable, return ``None``.  This could happen if the object
+   has been defined in C or in an interactive shell that does not retain source
+   code.
+
+   .. versionchanged:: next
+      Added support for type aliases created with the :keyword:`type` statement.
 
 
 .. function:: getfile(object)
@@ -763,6 +767,9 @@ Retrieving source code
    This will fail with a :exc:`TypeError` if the object is a built-in module,
    class, or function.
 
+   .. versionchanged:: next
+      Added support for :class:`~typing.TypeAliasType` objects.
+
 
 .. function:: getmodule(object)
 
@@ -778,36 +785,45 @@ Retrieving source code
    This will fail with a :exc:`TypeError` if the object is a built-in module,
    class, or function.
 
+   .. versionchanged:: next
+      Added support for :class:`~typing.TypeAliasType` objects.
+
 
 .. function:: getsourcelines(object)
 
    Return a list of source lines and starting line number for an object. The
-   argument may be a module, class, method, function, traceback, frame, or code
-   object.  The source code is returned as a list of the lines corresponding to the
-   object and the line number indicates where in the original source file the first
-   line of code was found.  An :exc:`OSError` is raised if the source code cannot
-   be retrieved.
+   argument may be a module, class, method, function, traceback, frame, code
+   object, or type alias.  The source code is returned as a list of the lines
+   corresponding to the object and the line number indicates where in the
+   original source file the first line of code was found.  An :exc:`OSError` is
+   raised if the source code cannot be retrieved.
    A :exc:`TypeError` is raised if the object is a built-in module, class, or
    function.
 
    .. versionchanged:: 3.3
       :exc:`OSError` is raised instead of :exc:`IOError`, now an alias of the
       former.
 
+   .. versionchanged:: next
+      Added support for type aliases created with the :keyword:`type` statement.
+
 
 .. function:: getsource(object)
 
    Return the text of the source code for an object. The argument may be a module,
-   class, method, function, traceback, frame, or code object.  The source code is
-   returned as a single string.  An :exc:`OSError` is raised if the source code
-   cannot be retrieved.
+   class, method, function, traceback, frame, code object, or type alias.  The
+   source code is returned as a single string.  An :exc:`OSError` is raised if the
+   source code cannot be retrieved.
    A :exc:`TypeError` is raised if the object is a built-in module, class, or
    function.
 
    .. versionchanged:: 3.3
       :exc:`OSError` is raised instead of :exc:`IOError`, now an alias of the
       former.
 
+   .. versionchanged:: next
+      Added support for type aliases created with the :keyword:`type` statement.
+
 
 .. function:: cleandoc(doc, *, dedent=True)
 

Lib/inspect.py

@@ -163,6 +163,7 @@
 from keyword import iskeyword
 from operator import attrgetter
 from collections import namedtuple, OrderedDict
+from _typing import TypeAliasType
 from _weakref import ref as make_weakref
 
 # Create constants for the compiler flags in Include/cpython/code.h
@@ -872,8 +873,18 @@ def getfile(object):
         object = object.f_code
     if iscode(object):
         return object.co_filename
-    raise TypeError('module, class, method, function, traceback, frame, or '
-                    'code object was expected, got {}'.format(
+    if isinstance(object, TypeAliasType):
+        evaluator = object.evaluate_value
+        if isfunction(evaluator):
+            return getfile(evaluator)
+        module = sys.modules.get(object.__module__)
+        if getattr(module, '__file__', None):
+            return module.__file__
+        if object.__module__ == '__main__':
+            raise OSError('source code not available')
+        raise TypeError(f'module not available for {object!r}')
+    raise TypeError('module, class, method, function, traceback, frame, '
+                    'code object, or type alias was expected, got {}'.format(
                     type(object).__name__))
 
 def getmodulename(path):
@@ -984,9 +995,14 @@ def findsource(object):
     """Return the entire source file and starting line number for an object.
 
     The argument may be a module, class, method, function, traceback, frame,
-    or code object.  The source code is returned as a list of all the lines
-    in the file and the line number indexes a line in that list.  An OSError
-    is raised if the source code cannot be retrieved."""
+    code object, or type alias.  The source code is returned as a list of all
+    the lines in the file and the line number indexes a line in that list.
+    An OSError is raised if the source code cannot be retrieved."""
+
+    if isinstance(object, TypeAliasType):
+        evaluator = object.evaluate_value
+        if isfunction(evaluator):
+            object = evaluator
 
     file = getsourcefile(object)
     if file:
@@ -1168,7 +1184,7 @@ def getsourcelines(object):
     """Return a list of source lines and starting line number for an object.
 
     The argument may be a module, class, method, function, traceback, frame,
-    or code object.  The source code is returned as a list of the lines
+    code object, or type alias.  The source code is returned as a list of the lines
     corresponding to the object and the line number indicates where in the
     original source file the first line of code was found.  An OSError is
     raised if the source code cannot be retrieved."""
@@ -1189,7 +1205,7 @@ def getsource(object):
     """Return the text of the source code for an object.
 
     The argument may be a module, class, method, function, traceback, frame,
-    or code object.  The source code is returned as a single string.  An
+    code object, or type alias.  The source code is returned as a single string.  An
     OSError is raised if the source code cannot be retrieved."""
     lines, lnum = getsourcelines(object)
     return ''.join(lines)

Lib/test/test_inspect/inspect_fodder.py

@@ -118,3 +118,6 @@ async def asyncf(self):
 # a closing parenthesis with the opening paren being in another line
 (
 ); after_closing = lambda: 1
+
+# What is their airspeed?
+type Sparrow = African | European

Lib/test/test_inspect/inspect_fodder2.py

@@ -400,4 +400,21 @@ def func394():
 def func400():
     return 401
 
+# A multiline generic alias.
+type GenericAlias[
+    T,
+] = (
+    list[T]
+    | tuple[T, ...]
+)
+
+class TypeAliases:
+    # A nested alias.
+    type Nested = MissingName
+
+def make_type_alias():
+    # A local alias.
+    type Local = MissingName
+    return Local
+
 pass # end of file

Lib/test/test_inspect/test_inspect.py

@@ -22,6 +22,7 @@
 import subprocess
 import time
 import types
+import typing
 import tempfile
 import textwrap
 import unicodedata
@@ -812,6 +813,7 @@ def test_getcomments(self):
         self.assertEqual(inspect.getcomments(mod), '# line 1\n')
         self.assertEqual(inspect.getcomments(mod.StupidGit), '# line 20\n')
         self.assertEqual(inspect.getcomments(mod2.cls160), '# line 159\n')
+        self.assertEqual(inspect.getcomments(mod.Sparrow), '# What is their airspeed?\n')
         # If the object source file is not available, return None.
         co = compile('x=1', '_non_existing_filename.py', 'exec')
         self.assertIsNone(inspect.getcomments(co))
@@ -851,6 +853,7 @@ def test_getsource(self):
         self.assertSourceEqual(mod.StupidGit, 21, 51)
         self.assertSourceEqual(mod.lobbest, 75, 76)
         self.assertSourceEqual(mod.after_closing, 120, 120)
+        self.assertSourceEqual(mod.Sparrow, 123, 123)
 
     def test_getsourcefile(self):
         self.assertEqual(normcase(inspect.getsourcefile(mod.spam)), modfile)
@@ -864,6 +867,31 @@ def test_getsourcefile(self):
         finally:
             del linecache.cache[co.co_filename]
 
+    def test_getsourcefile_type_alias(self):
+        self.assertEqual(normcase(inspect.getsourcefile(mod.Sparrow)),
+                         normcase(mod.__file__))
+        self.assertEqual(normcase(inspect.getfile(mod.Sparrow)),
+                         normcase(mod.__file__))
+
+        WrongModule = typing.TypeAliasType("WrongModule", int)
+        WrongModule.__module__ = "types"
+        self.assertEqual(normcase(inspect.getsourcefile(WrongModule)), normcase(types.__file__))
+        self.assertEqual(normcase(inspect.getfile(WrongModule)), normcase(types.__file__))
+
+        WrongModule.__module__ = "non-existing module"
+        with self.assertRaises(TypeError):
+            inspect.getsourcefile(WrongModule)
+        with self.assertRaises(TypeError):
+            inspect.getfile(WrongModule)
+
+    def test_getsource_on_generated_type_alias(self):
+        Alias = typing.TypeAliasType("Alias", int)
+        self.assertEqual(inspect.getsourcefile(Alias), __file__)
+        self.assertEqual(inspect.getfile(Alias), __file__)
+        self.assertRaises(OSError, inspect.getsource, Alias)
+        self.assertRaises(OSError, inspect.getsourcelines, Alias)
+        self.assertIsNone(inspect.getcomments(Alias))
+
     def test_getsource_empty_file(self):
         with temp_cwd() as cwd:
             with open('empty_file.py', 'w'):
@@ -1135,6 +1163,20 @@ def test_class_async_method(self):
 class TestBuggyCases(GetSourceBase):
     fodderModule = mod2
 
+    def test_type_aliases(self):
+        cases = (
+            (mod2.GenericAlias, 404, 409, '# A multiline generic alias.\n'),
+            (mod2.TypeAliases.Nested, 413, 413, '# A nested alias.\n'),
+            (mod2.make_type_alias(), 417, 417, '# A local alias.\n'),
+        )
+        for alias, start, end, comments in cases:
+            with self.subTest(alias=alias):
+                self.assertSourceEqual(alias, start, end)
+                self.assertEqual(inspect.getsourcelines(alias),
+                                 (self.sourcerange(start, end).splitlines(True),
+                                  start))
+                self.assertEqual(inspect.getcomments(alias), comments)
+
     def test_with_comment(self):
         self.assertSourceEqual(mod2.with_comment, 58, 59)
 
@@ -6920,6 +6962,32 @@ def f():
         expected = "The source is: <<<def f():\n    print(0)\n    return 1 + 2\n>>>"
         self.assertIn(expected, output)
 
+    @unittest.skipIf(not has_subprocess_support, "test requires subprocess")
+    def test_getsource_type_alias(self):
+        output = self.run_on_interactive_mode(textwrap.dedent("""\
+        type Alias = MissingName
+        import inspect
+        print(f"The source is: <<<{inspect.getsource(Alias)}>>>")
+        print(f"The lines are: {inspect.getsourcelines(Alias)!r}")
+        """))
+
+        self.assertIn("The source is: <<<type Alias = MissingName\n>>>", output)
+        self.assertIn("The lines are: (['type Alias = MissingName\\n'], 1)", output)
+
+    @unittest.skipIf(not has_subprocess_support, "test requires subprocess")
+    def test_getcomments_type_alias(self):
+        output = self.run_on_interactive_mode(textwrap.dedent("""\
+        def f():
+            # A local alias.
+            type Alias = MissingName
+            return Alias
+
+        import inspect
+        print(f"The comments are: <<<{inspect.getcomments(f())}>>>")
+        """))
+
+        self.assertIn("The comments are: <<<# A local alias.\n>>>", output)
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/NEWS.d/next/Library/2026-09-22-20-26-13.gh-issue-157955.DhpVD8.rst

@@ -0,0 +1,3 @@
+Support type alias objects in :func:`inspect.getcomments`,
+:func:`inspect.getfile`, :func:`inspect.getsourcefile`,
+:func:`inspect.getsourcelines`, and :func:`inspect.getsource`.