use ExceptionGroup for trio > 0.22

fixes #172

Author: belm0

.github/workflows/ci.yml

@@ -26,6 +26,24 @@ jobs:
       - run: make test
       - run: make lint
 
+  build_and_test_old_trio:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest]
+        python-version: ['3.7']
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Setup Python
+        uses: actions/setup-python@v3
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: 'pip'
+          cache-dependency-path: 'requirements-min.txt'
+      - run: pip install . -r requirements-min.txt && pip install trio==0.15.0 pytest-trio==0.7.0
+      - run: make test
+
   build_and_test_pypy:
     runs-on: ${{ matrix.os }}
     strategy:

setup.py

@@ -40,6 +40,7 @@
     keywords='websocket client server trio',
     packages=find_packages(exclude=['docs', 'examples', 'tests']),
     install_requires=[
+        'exceptiongroup',
         'trio>=0.11',
         'wsproto>=0.14',
     ],

trio_websocket/_impl.py

@@ -13,6 +13,7 @@
 
 import trio
 import trio.abc
+from exceptiongroup import BaseExceptionGroup
 from wsproto import ConnectionType, WSConnection
 from wsproto.connection import ConnectionState
 import wsproto.frame_protocol as wsframeproto
@@ -29,6 +30,7 @@
 )
 import wsproto.utilities
 
+_TRIO_MULTI_ERROR = tuple(map(int, trio.__version__.split('.'))) < (0, 22, 0)
 
 CONN_TIMEOUT = 60 # default connect & disconnect timeout, in seconds
 MESSAGE_QUEUE_SIZE = 1
@@ -37,6 +39,10 @@
 logger = logging.getLogger('trio-websocket')
 
 
+def _ignore_cancel(exc):
+    return None if isinstance(exc, trio.Cancelled) else exc
+
+
 class _preserve_current_exception:
     """A context manager which should surround an ``__exit__`` or
     ``__aexit__`` handler or the contents of a ``finally:``
@@ -59,10 +65,13 @@ def __exit__(self, ty, value, tb):
         if value is None or not self._armed:
             return False
 
-        def remove_cancels(exc):
-            return None if isinstance(exc, trio.Cancelled) else exc
-
-        return trio.MultiError.filter(remove_cancels, value) is None  # pylint: disable=no-member
+        if _TRIO_MULTI_ERROR:
+            filtered_exception = trio.MultiError.filter(_ignore_cancel, value)  # pylint: disable=no-member
+        elif isinstance(value, BaseExceptionGroup):
+            filtered_exception = value.subgroup(lambda exc: not isinstance(exc, trio.Cancelled))
+        else:
+            filtered_exception = _ignore_cancel(value)
+        return filtered_exception is None
 
 
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