Add a command-error hook when a command fails, from Hugh Davenport in

GitHub issue 3973.

cmd-queue.c

@@ -665,9 +665,18 @@ cmdq_fire_command(struct cmdq_item *item)
 
 out:
 	item->client = saved;
-	if (retval == CMD_RETURN_ERROR)
+	if (retval == CMD_RETURN_ERROR) {
+		fsp = NULL;
+		if (cmd_find_valid_state(&item->target))
+			fsp = &item->target;
+		else if (cmd_find_valid_state(&item->state->current))
+			fsp = &item->state->current;
+		else if (cmd_find_from_client(&fs, item->client, 0) == 0)
+			fsp = &fs;
+		cmdq_insert_hook(fsp != NULL ? fsp->s : NULL, item, fsp,
+		    "command-error");
 		cmdq_guard(item, "error", flags);
-	else
+	} else
 		cmdq_guard(item, "end", flags);
 	return (retval);
 }

options-table.c

@@ -1334,6 +1334,7 @@ const struct options_table_entry options_table[] = {
 	OPTIONS_TABLE_HOOK("client-focus-out", ""),
 	OPTIONS_TABLE_HOOK("client-resized", ""),
 	OPTIONS_TABLE_HOOK("client-session-changed", ""),
+	OPTIONS_TABLE_HOOK("command-error", ""),
 	OPTIONS_TABLE_PANE_HOOK("pane-died", ""),
 	OPTIONS_TABLE_PANE_HOOK("pane-exited", ""),
 	OPTIONS_TABLE_PANE_HOOK("pane-focus-in", ""),

tmux.1

@@ -4889,6 +4889,14 @@ layout after every
 set-hook -g after-split-window "selectl even-vertical"
 .Ed
 .Pp
+If a command fails, the
+.Ql command-error
+hook will be fired.
+For example, this could be used to write to a log file:
+.Bd -literal -offset indent
+set-hook -g command-error "run-shell \\"echo 'a tmux command failed' >>/tmp/log\\""
+.Ed
+.Pp
 All the notifications listed in the
 .Sx CONTROL MODE
 section are hooks (without any arguments), except
@@ -4921,6 +4929,8 @@ Run when focus exits a client
 Run when a client is resized.
 .It client-session-changed
 Run when a client's attached session is changed.
+.It command-error
+Run when a command fails.
 .It pane-died
 Run when the program running in a pane exits, but
 .Ic remain-on-exit