Close server socket handle when client side closes

We've so far relied on the user explicitly doing the `close` call, but
if they forget, the result is a server where new requests just pile up
due to the unclosed handles. Since `.close` is already idempotent (you
can call it many times on an async socket handle without problem), we
can simply close the handle when notified that the client side has
closed without any bad effects on existing code. Meanwhile, code that
doesn't bother will simply work. Change inspired by issue reported at
rakudo/rakudo#1775.

src/io/asyncsocket.c

@@ -55,33 +55,36 @@ static void on_read(uv_stream_t *handle, ssize_t nread, const uv_buf_t *buf) {
             MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
         });
     }
-    else if (nread == UV_EOF) {
-        MVMROOT2(tc, t, arr, {
-            MVMObject *final = MVM_repr_box_int(tc,
-                tc->instance->boot_types.BOOTInt, ri->seq_number);
-            MVM_repr_push_o(tc, arr, final);
-            MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
-            MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
-        });
-        if (buf->base)
-            MVM_free(buf->base);
-        uv_read_stop(handle);
-        MVM_io_eventloop_remove_active_work(tc, &(ri->work_idx));
-    }
     else {
-        MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTInt);
-        MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
-        MVMROOT2(tc, t, arr, {
-            MVMString *msg_str = MVM_string_ascii_decode_nt(tc,
-                tc->instance->VMString, uv_strerror(nread));
-            MVMObject *msg_box = MVM_repr_box_str(tc,
-                tc->instance->boot_types.BOOTStr, msg_str);
-            MVM_repr_push_o(tc, arr, msg_box);
-        });
+        MVMIOAsyncSocketData *handle_data = (MVMIOAsyncSocketData *)ri->handle->body.data;
+        uv_handle_t *conn_handle = (uv_handle_t *)handle_data->handle;
+        if (nread == UV_EOF) {
+            MVMROOT2(tc, t, arr, {
+                MVMObject *final = MVM_repr_box_int(tc,
+                    tc->instance->boot_types.BOOTInt, ri->seq_number);
+                MVM_repr_push_o(tc, arr, final);
+                MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
+                MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
+            });
+        }
+        else {
+            MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTInt);
+            MVM_repr_push_o(tc, arr, tc->instance->boot_types.BOOTStr);
+            MVMROOT2(tc, t, arr, {
+                MVMString *msg_str = MVM_string_ascii_decode_nt(tc,
+                    tc->instance->VMString, uv_strerror(nread));
+                MVMObject *msg_box = MVM_repr_box_str(tc,
+                    tc->instance->boot_types.BOOTStr, msg_str);
+                MVM_repr_push_o(tc, arr, msg_box);
+            });
+        }
         if (buf->base)
             MVM_free(buf->base);
-        uv_read_stop(handle);
         MVM_io_eventloop_remove_active_work(tc, &(ri->work_idx));
+        if (conn_handle && !uv_is_closing(conn_handle)) {
+            handle_data->handle = NULL;
+            uv_close(conn_handle, free_on_close_cb);
+        }
     }
     MVM_repr_push_o(tc, t->body.queue, arr);
 }