[huuan26]

All charmap encodings generated via Tools/unicode/gencodec.py implement Codec.decode by delegating directly to codecs.charmap_decode(input, errors, decoding_table) (which accepts any ReadableBuffer, just like IncrementalDecoder.decode in the same modules and cp1252.pyi).

This PR updates Codec.decode across all remaining gencodec.py-generated charmap encoding stubs in stdlib/encodings/ (cp*, hp_roman8, iso8859_*, koi8_*, kz1048, mac_*, palmos, ptcp154, tis_620) to accept ReadableBuffer instead of bytes.

[srittau]

Do you have a link to the implementation in CPython to verify this?

[huuan26]

Here are the links to the CPython implementation:

1. Lib/encodings/cp1250.py – cp1258.py (generated via Tools/unicode/gencodec.py):
   Codec.decode delegates directly to codecs.charmap_decode(input, errors, decoding_table) (just like IncrementalDecoder.decode, which is already typed with ReadableBuffer in these stubs):

   • https://github.com/python/cpython/blob/main/Lib/encodings/cp1250.py#L14-L15
   • https://github.com/python/cpython/blob/main/Lib/encodings/cp1252.py#L14-L15 (note: cp1252.pyi in typeshed already uses ReadableBuffer for Codec.decode)

2. Modules/_codecsmodule.c (_codecs.charmap_decode):
   In Argument Clinic, charmap_decode takes data: Py_buffer, accepting any ReadableBuffer (bytes, bytearray, memoryview, etc.), which matches _codecs.charmap_decode(data: ReadableBuffer, ...) in stdlib/_codecs.pyi:

   • https://github.com/python/cpython/blob/main/Modules/_codecsmodule.c#L351-L368

[JelleZijlstra]

Should we do this for a lot more of the encodings modules?

[huuan26]

Good call @JelleZijlstra! I audited all stdlib/encodings/*.pyi stubs and found 61 other gencodec.py-generated charmap encoding modules (cp037–cp1140, hp_roman8, iso8859_*, koi8_*, kz1048, mac_*, palmos, ptcp154, tis_620) that also delegate Codec.decode to codecs.charmap_decode(input, errors, decoding_table) (and already imported ReadableBuffer for IncrementalDecoder.decode).

I have updated all 61 remaining charmap encoding stubs in bc662da so they are all consistent.

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉