fix: convert positional-only parameters on methods, not just functions

[JarryShaw]

Fixes #20.

The bug

_process_classdef passes cls_ctx=name.name:

# <Name: ...>
name = node.name
...
self._process_suite_node(suite, cls_ctx=name.name)

parso.python.tree.Class.name already returns the Name leaf — as the comment on the line above says — and a parso Name keeps its string on .value. So every class body raised AttributeError: 'Name' object has no attribute 'name'.

Because bpc_utils' walker catches exceptions per node, the process still exited 0. Positional-only markers therefore survived into the output while the caller was told the conversion had succeeded — which matters for the subprocess.check_call integration the README recommends.

Plain module-level functions were unaffected, which is why this stayed hidden.

The fix

cls_ctx=name.value. That this is the intended value is clear from the surrounding contract:

• _process_suite_node(self, node, *, cls_ctx: Optional[str] = None) (poseur.py:442)
• stored as self._cls_ctx # type: Optional[str] (poseur.py:438)
• consumed by return self.mangle(self._cls_ctx, name) (poseur.py:1076)

Test

test_classdef covers the no-op case, the crash case, and the converted output. It fails on master:

$ python -m unittest test.TestPoseur.test_classdef
  File ".../poseur.py", line 744, in _process_classdef
    self._process_suite_node(suite, cls_ctx=name.name)
AttributeError: 'Name' object has no attribute 'name'
FAILED (errors=1)

and passes with the fix, along with the rest of the suite:

$ python -m unittest test
Ran 9 tests in 0.240s
OK

tests/sample.py contains no class statement at all, so the golden-file suite could never have caught this. The new test is written inline rather than by extending sample.py/sample.txt, to keep the fixtures untouched.

Real-world check

pcapkit/corekit/io.py from PyPCAPKit has 12 positional-only parameters spread across class bodies. With this change, walrus then poseur convert it into something CPython 3.7 parses cleanly:

$ python -m walrus --no-archive io.py && python -m poseur --no-archive io.py
$ grep -c ', /)' io.py ; grep -c ':=' io.py
0
0
$ python3.7 -c "import ast; ast.parse(open('io.py').read()); print('parses under 3.7')"
parses under 3.7

Verified on CPython 3.7.16 with parso 0.6.2 and bpc-utils 0.10.1.