Missing __nb_signature__ when running nanobind stubgen

[Theodor-Lindberg]

Hi,

We are using the nanobind stubgen tool from the Python module nanobind.stubgen in order to create stubs for our nanobind project. We develop the project on multiple machines, but some machines (i.e., not all) are plagued by this error of not finding __nb_signature__ when running nanobind.stubgen.

Are there any obvious dependencies missing that can cause this error, or anything along these lines? For most of our machines it works fine and this error is not present.

This setup:

• OS: RHEL 8
• Python 3.10 (Conda 24.5.0)
• nanobind 2.0.0

> python3 -m nanobind.stubgen -m apytypes._apytypes -o lib/apytypes/_apytypes.pyi
Module "apytypes._apytypes" ..
  - importing ..
  - analyzing ..
Traceback (most recent call last):
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/runpy.py", line 196, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 1392, in <module>
    main()
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 1363, in main
    sg.put(mod_imported)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 812, in put
    self.put(child, name=name, parent=value)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 819, in put
    self.put_type(value, name)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 520, in put_type
    self.put(v, k, tp)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 823, in put
    self.put_nb_func(value, name)
  File "/home/theli11/miniconda3/envs/py310/lib/python3.10/site-packages/nanobind/stubgen.py", line 366, in put_nb_func
    sigs = fn.__nb_signature__
AttributeError: 'nanobind.nb_method' object has no attribute '__nb_signature__'

[wjakob]

That's pretty weird. Is it possible that you are mixing extensions compiled with different versions of nanobind? The __nb_signature__ attribute exists in v2.0+. Please check carefully if there are maybe stale .so files lying around. If not, please provide a reproducer for this issue.

[Theodor-Lindberg]

The issue stemmed from having mixed versions like you suggested. There was an old 1.9.2 installation left on the system, and after removing it everything worked as expected. Thank you for the help.