api/msgpack-rpc: Implement channel_close and expose to vimscript

Simple function for closing a channel by id

src/nvim/eval.c

@@ -6306,6 +6306,7 @@ static struct fst {
   {"acos",            1, 1, f_acos},    /* WJMc */
   {"add",             2, 2, f_add},
   {"and",             2, 2, f_and},
+  {"api_close",       1, 1, f_api_close},
   {"api_spawn",       1, 2, f_api_spawn},
   {"append",          2, 2, f_append},
   {"argc",            0, 0, f_argc},
@@ -7054,6 +7055,26 @@ static void f_and(typval_T *argvars, typval_T *rettv)
                          & get_tv_number_chk(&argvars[1], NULL);
 }
 
+// "api_close(prog, argv)" function
+static void f_api_close(typval_T *argvars, typval_T *rettv)
+{
+  rettv->v_type = VAR_NUMBER;
+  rettv->vval.v_number = 0;
+
+  if (check_restricted() || check_secure()) {
+    return;
+  }
+
+  if (argvars[0].v_type != VAR_NUMBER) {
+    // Wrong argument types
+    EMSG(_(e_invarg));
+    return;
+  }
+
+  rettv->vval.v_number = channel_close(argvars[0].vval.v_number);
+}
+
+
 // "api_spawn(prog, argv)" function
 static void f_api_spawn(typval_T *argvars, typval_T *rettv)
 {

src/nvim/os/channel.c

@@ -267,6 +267,23 @@ void channel_unsubscribe(uint64_t id, char *event)
   unsubscribe(channel, event);
 }
 
+/// Closes a channel
+///
+/// @param id The channel id
+/// @return true if successful, false otherwise
+bool channel_close(uint64_t id)
+{
+  Channel *channel;
+
+  if (!(channel = pmap_get(uint64_t)(channels, id)) || !channel->enabled) {
+    return false;
+  }
+
+  channel_kill(channel);
+  channel->enabled = false;
+  return true;
+}
+
 /// Creates an API channel from stdin/stdout. This is used when embedding
 /// Neovim
 static void channel_from_stdio(void)
@@ -496,7 +513,13 @@ static void close_channel(Channel *channel)
 
   pmap_free(cstr_t)(channel->subscribed_events);
   kv_destroy(channel->call_stack);
+  channel_kill(channel);
 
+  free(channel);
+}
+
+static void channel_kill(Channel *channel)
+{
   if (channel->is_job) {
     if (channel->data.job) {
       job_stop(channel->data.job);
@@ -511,8 +534,6 @@ static void close_channel(Channel *channel)
       mch_exit(0);
     }
   }
-
-  free(channel);
 }
 
 static void close_cb(uv_handle_t *handle)