Ensure that pygls.Server uses the event loop it is given

Before this commit `pygls` would override the event loop for the
current thread even when given an existing loop to use.

Now `pygls` will rely on `asyncio.new_event_loop` to create the
appropriate event loop for the platform and only call it when
`loop=None`

This commit also introduces the `_own_loop` flag which is used to make
sure `pygls` does not close an event loop it does not own.

CHANGELOG.md

@@ -10,10 +10,18 @@ and this project adheres to [Semantic Versioning][semver].
 ### Changed
 ### Fixed
 
+- `pygls` no longer overrides the event loop for the current thread when given an explicit loop to use. ([#334])
+
+[#334]: https://github.com/openlawlibrary/pygls/issues/334
+
+
 ## [1.0.2] - May 15th, 2023
 ### Changed
 - Update typeguard to 3.x ([#327])
 
+[#327]: https://github.com/openlawlibrary/pygls/issues/327
+
+
 ### Fixed
 - Data files are no longer placed inside the wrong `site-packages` folder when installing `pygls` ([#232])
 [#232]: https://github.com/openlawlibrary/pygls/issues/232

pygls/server.py

@@ -23,7 +23,7 @@
 from threading import Event
 from typing import Any, Callable, List, Optional, TextIO, TypeVar, Union
 
-from pygls import IS_WIN, IS_PYODIDE
+from pygls import IS_PYODIDE
 from pygls.lsp import ConfigCallbackType, ShowDocumentCallbackType
 from pygls.exceptions import PyglsError, JsonRpcException, FeatureRequestError
 from lsprotocol.types import (
@@ -184,19 +184,14 @@ def __init__(self, protocol_cls, converter_factory, loop=None, max_workers=2,
         self._thread_pool_executor = None
         self.sync_kind = sync_kind
 
-        if IS_WIN:
-            asyncio.set_event_loop(asyncio.ProactorEventLoop())
-        elif not IS_PYODIDE:
-            asyncio.set_event_loop(asyncio.SelectorEventLoop())
-
-        self.loop = loop or asyncio.new_event_loop()
-
-        try:
-            if not IS_PYODIDE:
-                asyncio.get_child_watcher().attach_loop(self.loop)
-        except NotImplementedError:
-            pass
+        if loop is None:
+            loop = asyncio.new_event_loop()
+            asyncio.set_event_loop(loop)
+            self._owns_loop = True
+        else:
+            self._owns_loop = False
 
+        self.loop = loop
         self.lsp = protocol_cls(self, converter_factory())
 
     def shutdown(self):
@@ -216,8 +211,9 @@ def shutdown(self):
             self._server.close()
             self.loop.run_until_complete(self._server.wait_closed())
 
-        logger.info('Closing the event loop.')
-        self.loop.close()
+        if self._owns_loop and not self.loop.is_closed:
+            logger.info('Closing the event loop.')
+            self.loop.close()
 
     def start_io(self, stdin: Optional[TextIO] = None, stdout: Optional[TextIO] = None):
         """Starts IO server."""