Autogenerate signature for METH_NOARGS and perhaps METH_O extension functions

[anntzer]

BPO	40625
Nosy	@anntzer

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-05-14.11:46:04.481>
labels = ['expert-C-API', '3.9']
title = 'Autogenerate signature for METH_NOARGS and perhaps METH_O extension functions'
updated_at = <Date 2020-05-14.11:46:04.481>
user = 'https://github.com/anntzer'

bugs.python.org fields:

activity = <Date 2020-05-14.11:46:04.481>
actor = 'Antony.Lee'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['C API']
creation = <Date 2020-05-14.11:46:04.481>
creator = 'Antony.Lee'
dependencies = []
files = []
hgrepos = []
issue_num = 40625
keywords = []
message_count = 1.0
messages = ['368830']
nosy_count = 1.0
nosy_names = ['Antony.Lee']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue40625'
versions = ['Python 3.9']

Linked PRs

• gh-84805: Autogenerate signature for METH_NOARGS and METH_O extension functions #107794

[anntzer]

It would be nice if METH_NOARGS extension methods had an autogenerated signature (or rather, autogenerated __text_signature__ that gets picked up by inspect.signature). After all, the signature is trivially known at compile time.

The same could possibly be done for METH_O methods, for which the effective signature is known too. The name of the sole parameter is not known, but given that the parameter is (I believe?) positional only, that name "shouldn't" really matter (in the sense, e.g., that whether signature.bind() succeeds or not doesn't depend on the parameter name).

[serhiy-storchaka]

It is an interesting idea and I implemented it in #107794.

The one difference with Argument Clinic generated signature is that it names the first implicit argument $module in module-level functions and $self in unbound methods, while my PR use $self in both cases. But it does not matter, because it is always removed in module-level functions. The end user never sees a difference until it looks at __text_signature__ directly.