Backported Python 3.14 asyncio fix from dee0b942

Python 3.14 deprecated asyncio.get_event_loop() when there is no running
event loop. This backports the run_sync() helper function and its usage
from main branch to fix compatibility.

Refs #2506

datasette/cli.py

@@ -50,6 +50,17 @@ except ImportError:
     pass
 
 
+def run_sync(coro_func):
+    """Run an async callable to completion on a fresh event loop."""
+    loop = asyncio.new_event_loop()
+    try:
+        asyncio.set_event_loop(loop)
+        return loop.run_until_complete(coro_func())
+    finally:
+        asyncio.set_event_loop(None)
+        loop.close()
+
+
 class Config(click.ParamType):
     # This will be removed in Datasette 1.0 in favour of class Setting
     name = "config"
@@ -182,8 +193,7 @@ def inspect(files, inspect_file, sqlite_extensions):
     operations against immutable database files.
     """
     app = Datasette([], immutables=files, sqlite_extensions=sqlite_extensions)
-    loop = asyncio.get_event_loop()
-    inspect_data = loop.run_until_complete(inspect_(files, sqlite_extensions))
+    inspect_data = run_sync(lambda: inspect_(files, sqlite_extensions))
     if inspect_file == "-":
         sys.stdout.write(json.dumps(inspect_data, indent=2))
     else:
@@ -610,10 +620,10 @@ def serve(
         return ds
 
     # Run the "startup" plugin hooks
-    asyncio.get_event_loop().run_until_complete(ds.invoke_startup())
+    run_sync(ds.invoke_startup)
 
     # Run async soundness checks - but only if we're not under pytest
-    asyncio.get_event_loop().run_until_complete(check_databases(ds))
+    run_sync(lambda: check_databases(ds))
 
     if get:
         client = TestClient(ds)
@@ -633,9 +643,7 @@ def serve(
     if open_browser:
         if url is None:
             # Figure out most convenient URL - to table, database or homepage
-            path = asyncio.get_event_loop().run_until_complete(
-                initial_path_for_datasette(ds)
-            )
+            path = run_sync(lambda: initial_path_for_datasette(ds))
             url = f"http://{host}:{port}{path}"
         webbrowser.open(url)
     uvicorn_kwargs = dict(