extmod/uasyncio: Get addr and bind server socket before creating task.

Currently when using uasyncio.start_server() the socket configuration is
done inside a uasyncio.create_task() background function.  If the address
and port are already in use however this throws an OSError which cannot be
cleanly caught behind the create_task().

This commit moves the getaddrinfo and socket binding to the start_server()
function, and only creates the task if that succeeds.  This means that any
OSError from the initial socket configuration is propagated directly up the
call stack, compatible with CPython behaviour.

See #7444.

Signed-off-by: Damien George <damien@micropython.org>

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/net_hosted/uasyncio_start_server.py b/tests/net_hosted/uasyncio_start_server.py
new file mode 100644
index 0000000000..f13402979f
--- /dev/null
+++ b/tests/net_hosted/uasyncio_start_server.py
@@ -0,0 +1,31 @@
+# Test basic behaviour of uasyncio.start_server()
+
+try:
+    import uasyncio as asyncio
+except ImportError:
+    try:
+        import asyncio
+    except ImportError:
+        print("SKIP")
+        raise SystemExit
+
+
+async def test():
+    # Test creating 2 servers using the same address
+    print("create server1")
+    server1 = await asyncio.start_server(None, "0.0.0.0", 8000)
+    try:
+        print("create server2")
+        await asyncio.start_server(None, "0.0.0.0", 8000)
+    except OSError as er:
+        print("OSError")
+
+    # Wait for server to close.
+    async with server1:
+        print("sleep")
+        await asyncio.sleep(0)
+
+    print("done")
+
+
+asyncio.run(test())