Added running_in_another_thread()

Tests/helper.py

@@ -4,6 +4,7 @@ Helper functions.
 
 from __future__ import annotations
 
+import inspect
 import logging
 import os
 import shutil
@@ -29,6 +30,8 @@ if os.environ.get("SHOW_ERRORS"):
 elif "GITHUB_ACTIONS" in os.environ:
     uploader = "github_actions"
 
+already_running = []
+
 
 def upload(a: Image.Image, b: Image.Image) -> str | None:
     if uploader == "show":
@@ -165,6 +168,18 @@ def assert_tuple_approx_equal(
             pytest.fail(msg + ": " + repr(actuals) + " != " + repr(targets))
 
 
+def running_in_another_thread() -> bool:
+    frameInfo = inspect.stack()[1]
+    identifier = (
+        frameInfo.filename + ":" + frameInfo.function + ":" + str(frameInfo.lineno)
+    )
+    if identifier in already_running:
+        return True
+
+    already_running.append(identifier)
+    return False
+
+
 def skip_unless_feature(feature: str) -> pytest.MarkDecorator:
     reason = f"{feature} not available"
     return pytest.mark.skipif(not features.check(feature), reason=reason)

Tests/test_core_resources.py

@@ -6,7 +6,7 @@ import pytest
 
 from PIL import Image
 
-from .helper import is_pypy
+from .helper import is_pypy, running_in_another_thread
 
 
 def test_get_stats() -> None:
@@ -48,6 +48,9 @@ class TestCoreMemory:
         assert alignment > 0
 
     def test_set_alignment(self) -> None:
+        if running_in_another_thread():
+            return
+
         for i in [1, 2, 4, 8, 16, 32]:
             Image.core.set_alignment(i)
             alignment = Image.core.get_alignment()

Tests/test_file_bufrstub.py

@@ -7,7 +7,7 @@ import pytest
 
 from PIL import BufrStubImagePlugin, Image, ImageFile
 
-from .helper import hopper
+from .helper import hopper, running_in_another_thread
 
 TEST_FILE = "Tests/images/gfs.t06z.rassda.tm00.bufr_d"
 
@@ -70,6 +70,9 @@ def test_handler(tmp_path: Path) -> None:
         def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
             self.saved = True
 
+    if running_in_another_thread():
+        return
+
     handler = TestHandler()
     BufrStubImagePlugin.register_handler(handler)
     with Image.open(TEST_FILE) as im:

Tests/test_file_gribstub.py

@@ -7,7 +7,7 @@ import pytest
 
 from PIL import GribStubImagePlugin, Image, ImageFile
 
-from .helper import hopper
+from .helper import hopper, running_in_another_thread
 
 TEST_FILE = "Tests/images/WAlaska.wind.7days.grb"
 
@@ -70,6 +70,9 @@ def test_handler(tmp_path: Path) -> None:
         def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
             self.saved = True
 
+    if running_in_another_thread():
+        return
+
     handler = TestHandler()
     GribStubImagePlugin.register_handler(handler)
     with Image.open(TEST_FILE) as im:

Tests/test_file_hdf5stub.py

@@ -8,6 +8,8 @@ import pytest
 
 from PIL import Hdf5StubImagePlugin, Image, ImageFile
 
+from .helper import running_in_another_thread
+
 TEST_FILE = "Tests/images/hdf5.h5"
 
 
@@ -72,6 +74,9 @@ def test_handler(tmp_path: Path) -> None:
         def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
             self.saved = True
 
+    if running_in_another_thread():
+        return
+
     handler = TestHandler()
     Hdf5StubImagePlugin.register_handler(handler)
     with Image.open(TEST_FILE) as im:

Tests/test_file_wmf.py

@@ -8,7 +8,7 @@ import pytest
 
 from PIL import Image, ImageFile, WmfImagePlugin
 
-from .helper import assert_image_similar_tofile, hopper
+from .helper import assert_image_similar_tofile, hopper, running_in_another_thread
 
 
 def test_load_raw() -> None:
@@ -45,6 +45,9 @@ def test_register_handler(tmp_path: Path) -> None:
         def save(self, im: Image.Image, fp: IO[bytes], filename: str) -> None:
             self.methodCalled = True
 
+    if running_in_another_thread():
+        return
+
     handler = TestHandler()
     original_handler = WmfImagePlugin._handler
     WmfImagePlugin.register_handler(handler)