Add tsan to docker test matrix

.github/workflows/test-docker.yml

@@ -42,6 +42,7 @@ jobs:
           arch,
           centos-stream-9-amd64,
           centos-stream-10-amd64,
+          cpython_sanity-3.14tsan,
           debian-13-trixie-x86,
           debian-13-trixie-amd64,
           fedora-43-amd64,

Tests/conftest.py

@@ -1,17 +1,24 @@
 from __future__ import annotations
 
 import io
+import os
 import sys
 import sysconfig
 
 import pytest
 
+TYPE_CHECKING = False
+if TYPE_CHECKING:
+    from collections.abc import Generator
+
 FREE_THREADED_BUILD = bool(sysconfig.get_config_var("Py_GIL_DISABLED"))
 
 gil_enabled_at_start = True
 if FREE_THREADED_BUILD:
     gil_enabled_at_start = sys._is_gil_enabled()  # type: ignore[attr-defined]
 
+TSAN_ENABLED = os.environ.get("PILLOW_TSAN_TEST") == "1"
+
 
 def pytest_report_header(config: pytest.Config) -> str:
     try:
@@ -60,3 +67,16 @@ def pytest_configure(config: pytest.Config) -> None:
     except Exception:
         # valgrind is already installed
         pass
+
+
+@pytest.fixture(autouse=TSAN_ENABLED)
+def tsan_parse(capfd: pytest.CaptureFixture[str]) -> Generator[None]:
+    # TSAN has two error modes, return a non-zero return code from the process
+    # or stop on error. Neither of these are really useful for us in a longrunning
+    # process, so we're hacking around this by reading stderr and looking for the
+    # TSAN Warning.
+    yield
+    out, err = capfd.readouterr()
+    if "WARNING: ThreadSanitizer" in err:
+        msg = "ThreadSanitizer Warning"
+        raise Exception(msg)