Fix: get_spec() in funcy/_inspect.py looked up manual arg-spec overrides... - #176
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Fix: get_spec() in funcy/_inspect.py looked up manual arg-spec overrides...#176M001N wants to merge 1 commit into
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…swith get_spec() only looked up manual arg-spec overrides by __module__, but method descriptors of builtin types (e.g. str.endswith) have no __module__, so it fell through to signature() which raises on descriptors lacking a valid __text_signature__ -- turned into a bare ValueError. Extend the override mechanism to also key off __objclass__.__name__ (the owning builtin type), analogous to the existing module-keyed ARGS table, and add entries for str.startswith/str.endswith. Fixes Suor#108
Suor
reviewed
Aug 17, 2026
| # keyed by the owning type's name (func.__objclass__.__name__), mirroring how | ||
| # ARGS[mod] works for module-level builtins above. These cover builtin methods | ||
| # whose __text_signature__ is missing/invalid, so signature() can't handle them. | ||
| ARGS['str'] = { |
Owner
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Should be a separate namespace for this. Should look how much this is needed outside of str.endswith example
Suor
reviewed
Aug 17, 2026
| # whose __text_signature__ is missing/invalid, so signature() can't handle them. | ||
| ARGS['str'] = { | ||
| 'startswith': 'self,prefix', | ||
| 'endswith': 'self,suffix', |
Suor
reviewed
Aug 17, 2026
| Spec = namedtuple("Spec", "max_n names req_n req_names varkw") | ||
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| def _spec_from_str(_spec): |
Owner
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Should go after get_spec() - we have top-down order in this file
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Summary
Extended the manual-override mechanism in funcy/_inspect.py: added a
_spec_from_str()helper factoring out the existing spec-string-to-Spec parsing logic, and a new lookup keyed byfunc.__objclass__.__name__(available on builtin method descriptors) checked alongside the existing module-keyed lookup in get_spec(). Added ARGS['str'] with entries for 'startswith' ('self,prefix') and 'endswith' ('self,suffix') -- the two methods that actually fail signature() introspection on modern CPython. Deliberately did not add str.split/replace/join since those already introspect correctly via signature() (verified: only startswith/endswith raise 'builtin has invalid signature' on this Python version) and adding overrides for them would have dropped their keyword-argument support (used by an existing autocurry(str.split) test), since the override mechanism doesn't track argument names.Problem
Suor/funcy issue reference: #108
Root Cause
get_spec() in funcy/_inspect.py looked up manual arg-spec overrides only via
mod = getattr(func, '__module__', None)against the module-keyed ARGS table. str.endswith is a method_descriptor with no module (falls back to None), so it never matched ARGS['builtins']. It also has no code and is not a type, so execution fell through to the finalsignature(func)call, which raises on this descriptor (no valid text_signature), and funcy re-raises that as a plain ValueError, masking a fixable introspection gap.Testing
PASS - all 206 tests in the full suite pass, including the new regression test and all pre-existing curry/rcurry/autocurry tests.
Related Issue
#108