8000 Cython 3.1 compatibility · Issue #1575 · python-zeroconf/python-zeroconf · GitHub
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mgorny opened this issue May 3, 2025 · 4 comments
Closed

Cython 3.1 compatibility #1575

mgorny opened this issue May 3, 2025 · 4 comments

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@mgorny
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mgorny commented May 3, 2025

Cython 3.1.0 is in RC phase already, so we can expect a final release sooner than later. As #1559 shows, zeroconf currently doesn't work with it and I wasn't able to find any tracking issue for the issues.

I have been trying to fix it myself but I'm afraid it's above my pay grade. From what I gather, Cython 3.1 got better at type annotations in .py files, and all the issues I've hit were somehow related to type annotations.

I've filed #1574 to fix one case of low-hanging fruit.

Another issue I've noticed is the type mismatch in DNSRecord.ttl:

python-zeroconf/src/zeroconf/_dns.pxd

Lines 45 to 47 in f5c15e9

cdef class DNSRecord(DNSEntry):
cdef public cython.float ttl

python-zeroconf/src/zeroconf/_dns.py

Lines 164 to 178 in f5c15e9

class DNSRecord(DNSEntry):
"""A DNS record - like a DNS entry, but has a TTL"""
__slots__ = ("created", "ttl")
# TODO: Switch to just int ttl
def __init__(
self,
name: str,
type_: int,
class_: int,
ttl: float | int,
created: float | None = None,
) -> None:
self._fast_init_record(name, type_, class_, ttl, created or current_time_millis())

Other signature mismatches I couldn't grasp. It is possible that they are actually a bug in Cython, but I don't really know Cython, so I'd appreciate if someone with better understanding of it checked, and possibly reported a bug upstream.

FWICS I can reproduce the same error with the following minimal reproducer:

.pxd:

cdef void foo(object x);

.py:

def foo(x: int) -> None:
    ...

but I don't know how int is supposed to be mapped here.
@bdraco
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bdraco commented May 3, 2025

I have ~16 projects that I’m working on that don’t work with 3.1.x. I’m working through the smaller ones first. It’s going to take a while to get here. If it ships before I get to it, I’ll do a new release to pin Cython

@bdraco
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bdraco commented May 3, 2025

We use object when we don’t want Cython to convert it to a native type and we want a PyInt.

Usual workaround it to assign the type to _int = int and than change the type to _int. That has prevented Cython from converting it

@mgorny
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mgorny commented May 3, 2025

There's also the possibility of using "annotation_typing": False directive, but that's a kind of big cannon.

@bdraco
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bdraco commented May 3, 2025

Fixed in master, release pending

@bdraco bdraco closed this as completed May 3, 2025
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