[Python] Why does inspect fail to get source file for classes in a dynamically-imported module?

inspect.getsource() and inspect.getsourcefile() can access source info for a function, but not for a class, when they are in a module that is imported dynamically with importlib.

Here are two files, thing1.py and thing2.py:

• 
  thing1.py
  
  import inspect
  import os
  import importlib.util
  
  dir_here = os.path.dirname(__file__)
  spec = importlib.util.spec_from_file_location("thing2",
  os.path.join(dir_here, "thing2.py"))
  module = importlib.util.module_from_spec(spec)
  spec.loader.exec_module(module)
  
  print(module.foo(3))
  print(module.Bar().inc(3))
  
  print("module source file:", inspect.getsourcefile(module))
  for attr in ['foo','Bar']:
  print("%s source: %s" % (attr, inspect.getsourcefile(getattr(module, attr))))
  print(inspect.getsource(getattr(module, attr)))
• 
  thing2.py
  
  def foo(x):
  return x+1
  
  class Bar(object):
  def inc(self, x):
  return x+1

If I run test1.py here's what I get:

> python c:\tmp\python\test2\thing1.py
4
4
module source file: c:\tmp\python\test2\thing2.py
foo source: c:\tmp\python\test2\thing2.py
def foo(x):
return x+1

Traceback (most recent call last):
File "c:\tmp\python\test2\thing1.py", line 16, in <module>
print("%s source: %s" % (attr, inspect.getsourcefile(getattr(module, attr))))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\jason\.conda\envs\py3datalab\Lib\inspect.py", line 940, in getsourcefile
filename = getfile(object)
^^^^^^^^^^^^^^^
File "C:\Users\jason\.conda\envs\py3datalab\Lib\inspect.py", line 909, in getfile
raise TypeError('{!r} is a built-in class'.format(object))
TypeError: <class 'thing2.Bar'> is a built-in class


I'm using Python 3.11.4.

Am I missing something during my import step that tells Python how to get source info for classes?

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