Modernize test_inspect by adding real pos-only parameters

Right now test_inspect uses several hacks to pretend that some parameters are positional only:

Lines 2465 to 2469 in ecad802

    
           def test(po, pk, pod=42, pkd=100, *args, ko, **kwargs): 
        
               pass 
        
           sig = inspect.signature(test) 
        
           po = sig.parameters['po'].replace(kind=P.POSITIONAL_ONLY) 
        
           pod = sig.parameters['pod'].replace(kind=P.POSITIONAL_ONLY)

cpython/Lib/test/test_inspect.py

Lines 2519 to 2522 in ecad802

    
           myparam = MyParameter(name='z', kind=inspect.Parameter.POSITIONAL_ONLY) 
        
           myparams = collections.OrderedDict(sig.parameters, a=myparam) 
        
           mysig = MySignature().replace(parameters=myparams.values(), 
        
                                         return_annotation=sig.return_annotation)

cpython/Lib/test/test_inspect.py

Lines 3047 to 3052 in ecad802

    
           def foo(a, b, c, d, **kwargs): 
        
               pass 
        
           sig = inspect.signature(foo) 
        
           params = sig.parameters.copy() 
        
           params['a'] = params['a'].replace(kind=Parameter.POSITIONAL_ONLY) 
        
           params['b'] = params['b'].replace(kind=Parameter.POSITIONAL_ONLY)

cpython/Lib/test/test_inspect.py

Lines 3559 to 3565 in ecad802

    
           def test(a_po, *, b, **kwargs): 
        
               return a_po, kwargs 
        
           sig = inspect.signature(test) 
        
           new_params = list(sig.parameters.values()) 
        
           new_params[0] = new_params[0].replace(kind=P.POSITIONAL_ONLY) 
        
           test.__signature__ = sig.replace(parameters=new_params)

cpython/Lib/test/test_inspect.py

Lines 4160 to 4166 in ecad802

    
           def test(a_po, b_po, c_po=3, foo=42, *, bar=50, **kwargs): 
        
               return a_po, b_po, c_po, foo, bar, kwargs 
        
           sig = inspect.signature(test) 
        
           new_params = collections.OrderedDict(tuple(sig.parameters.items())) 
        
           for name in ('a_po', 'b_po', 'c_po'): 
        
               new_params[name] = new_params[name].replace(kind=P.POSITIONAL_ONLY)

And maybe others.

It makes code more complex, unclear, and hides the real purpose of these tests.

This is not a design decision, but rather a limitation at the time. Commits are quite old and pos-only syntax was not available 9 and 11 years ago:

So, I propose to simplify these tests and make them more correct by using explicit pos only parameters.

Plus, we can keep one test like this to be sure that chaning a parameter kind still works as before. But, there's no need in keeping these old tests the way they are.

I will send a PR with the fix 👍

Linked PRs

Since all supported Python versions have pos-only parameters this can be backported to reduce the amount of potential future merge conflicts.

Ok, some code samples that I've listed cannot be replaced, because they test different things. But, some - can be.

pythongh-103406: Modernize pos-only arguments usage in `test_signature`

pythongh-103406: Modernize pos-only arguments usage in `test_signatur…

gh-103406: Modernize pos-only arguments usage in `test_signature` (#1…

gh-103406: Modernize pos-only arguments usage in `test_signature` (GH…

Merge branch 'main' into superopt

Merge branch 'superopt' into superopt_spec

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Modernize `test_inspect` by adding real pos-only parameters #103406

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	def test(po, pk, pod=42, pkd=100, args, ko, *kwargs):
	pass
	sig = inspect.signature(test)
	po = sig.parameters['po'].replace(kind=P.POSITIONAL_ONLY)
	pod = sig.parameters['pod'].replace(kind=P.POSITIONAL_ONLY)

	myparam = MyParameter(name='z', kind=inspect.Parameter.POSITIONAL_ONLY)
	myparams = collections.OrderedDict(sig.parameters, a=myparam)
	mysig = MySignature().replace(parameters=myparams.values(),
	return_annotation=sig.return_annotation)

	def foo(a, b, c, d, **kwargs):
	pass
	sig = inspect.signature(foo)
	params = sig.parameters.copy()
	params['a'] = params['a'].replace(kind=Parameter.POSITIONAL_ONLY)
	params['b'] = params['b'].replace(kind=Parameter.POSITIONAL_ONLY)

	def test(a_po, , b, *kwargs):
	return a_po, kwargs

	sig = inspect.signature(test)
	new_params = list(sig.parameters.values())
	new_params[0] = new_params[0].replace(kind=P.POSITIONAL_ONLY)
	test.__signature__ = sig.replace(parameters=new_params)

	def test(a_po, b_po, c_po=3, foo=42, , bar=50, *kwargs):
	return a_po, b_po, c_po, foo, bar, kwargs

	sig = inspect.signature(test)
	new_params = collections.OrderedDict(tuple(sig.parameters.items()))
	for name in ('a_po', 'b_po', 'c_po'):
	new_params[name] = new_params[name].replace(kind=P.POSITIONAL_ONLY)

Modernize test_inspect by adding real pos-only parameters #103406

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sobolevn commented on Apr 10, 2023

sobolevn commented on Apr 10, 2023

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Modernize `test_inspect` by adding real pos-only parameters #103406