feat(startup): validate --listen address

Problem:
`nvim --listen` does not error on EADDRINUSE. #30123

Solution:
Now that `$NVIM_LISTEN_ADDRESS` is deprecated and input *only* (instead
of the old, ambiguous situation where it was both an input *and* an
output), we can be fail fast instead of trying to "recover". This
reverts the "recovery" behavior of
704ba4151e7f67999510ee0ac19fdabb595d530c, but that was basically
a workaround for the fragility of `$NVIM_LISTEN_ADDRESS`.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/nvim/api/ui.c b/src/nvim/api/ui.c
index a99d97acb8..5dc373acdc 100644
--- a/src/nvim/api/ui.c
+++ b/src/nvim/api/ui.c
@@ -93,15 +93,15 @@ void remote_ui_free_all_mem(void)
 }
 #endif
 
-/// Wait until ui has connected on stdio channel if only_stdio
-/// is true, otherwise any channel.
+/// Wait until UI has connected.
+///
+/// @param only_stdio UI is expected to connect on stdio.
 void remote_ui_wait_for_attach(bool only_stdio)
 {
   if (only_stdio) {
     Channel *channel = find_channel(CHAN_STDIO);
     if (!channel) {
-      // this function should only be called in --embed mode, stdio channel
-      // can be assumed.
+      // `only_stdio` implies --embed mode, thus stdio channel can be assumed.
       abort();
     }