Make the test suite work with 3.15

.github/workflows/ci.yml

@@ -168,7 +168,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.10', '3.11', '3.12', '3.13', '3.14', '3.14t']
+        python: ['3.10', '3.11', '3.12', '3.13', '3.14', '3.14t', '3.15-dev']
         arch: ['x86', 'x64']
         lsp: ['']
         lsp_extract_file: ['']
@@ -242,7 +242,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['pypy-3.11', '3.10', '3.11', '3.12', '3.13', '3.14', '3.14t']
+        python: ['pypy-3.11', '3.10', '3.11', '3.12', '3.13', '3.14', '3.14t', '3.15-dev']
         check_formatting: ['0']
         no_test_requirements: ['0']
         extra_name: ['']
@@ -320,7 +320,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['pypy-3.11', '3.10', '3.11', '3.12', '3.13', '3.14', '3.14t']
+        python: ['pypy-3.11', '3.10', '3.11', '3.12', '3.13', '3.14', '3.14t', '3.15-dev']
     continue-on-error: >-
       ${{
         (

newsfragments/3456.feature.rst

@@ -0,0 +1,2 @@
+Support Python 3.15, as of beta 3. Things may still change and so this
+support may break in the future.

pyproject.toml

@@ -233,6 +233,8 @@ filterwarnings = [
   'ignore:You are using cryptography on a 32-bit Python on a 64-bit Windows Operating System. Cryptography will be significantly faster if you switch to using a 64-bit Python.:UserWarning',
   # https://github.com/berkerpeksag/astor/issues/217
   'ignore:ast.Num is deprecated:DeprecationWarning:astor',
+  # https://github.com/coveragepy/coveragepy/issues/2208
+  'ignore:Module globals; __loader__ != __spec__.loader:DeprecationWarning',
 ]
 junit_family = "xunit2"
 markers = ["redistributors_should_skip: tests that should be skipped by downstream redistributors"]

src/trio/_core/_tests/test_thread_cache.py

@@ -1,8 +1,10 @@
 from __future__ import annotations
 
 import os
+import sys
 import threading
 import time
+import warnings
 from contextlib import contextmanager
 from queue import Queue
 from typing import TYPE_CHECKING, NoReturn
@@ -210,7 +212,17 @@ def foo() -> None:
     start_thread_soon(foo, lambda _: done.set())
     done.wait()
 
-    child_pid = os.fork()
+    with warnings.catch_warnings(record=True) as emitted:
+        # TODO: remove this extra filter once we drop 3.14. See
+        # https://github.com/python-trio/trio/issues/3355.
+        warnings.simplefilter("default")
+        child_pid = os.fork()
+
+    if child_pid != 0 and sys.version_info >= (3, 12):
+        # the warning is only emitted in the parent
+        assert len(emitted) == 1
+        assert isinstance(emitted[0].message, DeprecationWarning)
+        assert "fork() may lead to" in str(emitted[0].message)
 
     # try using it
     done = threading.Event()

src/trio/_tests/test_exports.py

@@ -426,6 +426,10 @@ def lookup_symbol(symbol: str) -> dict[str, Any]:  # type: ignore[misc, explicit
             extra = {e for e in extra if not e.endswith("AttrsAttributes__")}
             assert len(extra) == before - 1
 
+        if issubclass(class_, trio.Path) and sys.version_info >= (3, 15):
+            # needs a typeshed update for https://github.com/python/typeshed/pull/15737
+            extra.remove("is_reserved")
+
         if attrs.has(class_):
             # dynamically created attribute by attrs?
             missing.remove("__attrs_props__")

src/trio/socket.py

@@ -253,6 +253,33 @@
         CAN_ERR_FLAG as CAN_ERR_FLAG,
         CAN_ERR_MASK as CAN_ERR_MASK,
         CAN_ISOTP as CAN_ISOTP,
+        CAN_ISOTP_CHK_PAD_DATA as CAN_ISOTP_CHK_PAD_DATA,
+        CAN_ISOTP_CHK_PAD_LEN as CAN_ISOTP_CHK_PAD_LEN,
+        CAN_ISOTP_DEFAULT_EXT_ADDRESS as CAN_ISOTP_DEFAULT_EXT_ADDRESS,
+        CAN_ISOTP_DEFAULT_FLAGS as CAN_ISOTP_DEFAULT_FLAGS,
+        CAN_ISOTP_DEFAULT_FRAME_TXTIME as CAN_ISOTP_DEFAULT_FRAME_TXTIME,
+        CAN_ISOTP_DEFAULT_LL_MTU as CAN_ISOTP_DEFAULT_LL_MTU,
+        CAN_ISOTP_DEFAULT_LL_TX_DL as CAN_ISOTP_DEFAULT_LL_TX_DL,
+        CAN_ISOTP_DEFAULT_LL_TX_FLAGS as CAN_ISOTP_DEFAULT_LL_TX_FLAGS,
+        CAN_ISOTP_DEFAULT_PAD_CONTENT as CAN_ISOTP_DEFAULT_PAD_CONTENT,
+        CAN_ISOTP_DEFAULT_RECV_BS as CAN_ISOTP_DEFAULT_RECV_BS,
+        CAN_ISOTP_DEFAULT_RECV_STMIN as CAN_ISOTP_DEFAULT_RECV_STMIN,
+        CAN_ISOTP_DEFAULT_RECV_WFTMAX as CAN_ISOTP_DEFAULT_RECV_WFTMAX,
+        CAN_ISOTP_EXTEND_ADDR as CAN_ISOTP_EXTEND_ADDR,
+        CAN_ISOTP_FORCE_RXSTMIN as CAN_ISOTP_FORCE_RXSTMIN,
+        CAN_ISOTP_FORCE_TXSTMIN as CAN_ISOTP_FORCE_TXSTMIN,
+        CAN_ISOTP_HALF_DUPLEX as CAN_ISOTP_HALF_DUPLEX,
+        CAN_ISOTP_LISTEN_MODE as CAN_ISOTP_LISTEN_MODE,
+        CAN_ISOTP_LL_OPTS as CAN_ISOTP_LL_OPTS,
+        CAN_ISOTP_OPTS as CAN_ISOTP_OPTS,
+        CAN_ISOTP_RECV_FC as CAN_ISOTP_RECV_FC,
+        CAN_ISOTP_RX_EXT_ADDR as CAN_ISOTP_RX_EXT_ADDR,
+        CAN_ISOTP_RX_PADDING as CAN_ISOTP_RX_PADDING,
+        CAN_ISOTP_RX_STMIN as CAN_ISOTP_RX_STMIN,
+        CAN_ISOTP_SF_BROADCAST as CAN_ISOTP_SF_BROADCAST,
+        CAN_ISOTP_TX_PADDING as CAN_ISOTP_TX_PADDING,
+        CAN_ISOTP_TX_STMIN as CAN_ISOTP_TX_STMIN,
+        CAN_ISOTP_WAIT_TX_DONE as CAN_ISOTP_WAIT_TX_DONE,
         CAN_J1939 as CAN_J1939,
         CAN_RAW as CAN_RAW,
         CAN_RAW_ERR_FILTER as CAN_RAW_ERR_FILTER,
@@ -400,6 +427,7 @@
         IPV6_CHECKSUM as IPV6_CHECKSUM,
         IPV6_DONTFRAG as IPV6_DONTFRAG,
         IPV6_DSTOPTS as IPV6_DSTOPTS,
+        IPV6_HDRINCL as IPV6_HDRINCL,
         IPV6_HOPLIMIT as IPV6_HOPLIMIT,
         IPV6_HOPOPTS as IPV6_HOPOPTS,
         IPV6_JOIN_GROUP as IPV6_JOIN_GROUP,
@@ -575,6 +603,7 @@
         SOL_ALG as SOL_ALG,
         SOL_BLUETOOTH as SOL_BLUETOOTH,
         SOL_CAN_BASE as SOL_CAN_BASE,
+        SOL_CAN_ISOTP as SOL_CAN_ISOTP,
         SOL_CAN_RAW as SOL_CAN_RAW,
         SOL_HCI as SOL_HCI,
         SOL_IP as SOL_IP,