Description

sobolevn

opened on Apr 10, 2023

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

cpython/Lib/test/test_inspect.py

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:

• 3f73ca2
• 7c7cbfc

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

• gh-103406: Modernize pos-only arguments usage in test_signature #103407
• [3.11] gh-103406: Modernize pos-only arguments usage in test_signature (GH-103407) #103536

Activity

1. sobolevn

   added

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   testsTests in the Lib/test dirTests in the Lib/test dir

   on Apr 10, 2023
2. sobolevn

   self-assigned this

   on Apr 10, 2023
3. sobolevn commented on Apr 10, 2023

   

   sobolevn

   on Apr 10, 2023

   MemberAuthor

   More actions

   Since all supported Python versions have pos-only parameters this can be backported to reduce the amount of potential future merge conflicts.
4. sobolevn commented on Apr 10, 2023

   

   sobolevn

   on Apr 10, 2023

   MemberAuthor

   More actions

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

   added a commit that references this issue on Apr 10, 2023

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

   f06ee15
6. miss-islington

   added a commit that references this issue on Apr 14, 2023

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

   4114451
7. JelleZijlstra

   added a commit that references this issue on Apr 14, 2023

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

   7569781
8. miss-islington

   added a commit that references this issue on Apr 14, 2023

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

   2e0ead5
9. carljm

   added 2 commits that reference this issue on Apr 14, 2023

   Merge branch 'main' into superopt

   64da49f

   Merge branch 'superopt' into superopt_spec

   b73cff0
10. sobolevn

    closed this as completedon Apr 15, 2023

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