bar: fix segfault with missing or invalid bar id

Prior to this patch, if I ran something like this, sway would crash:

    swaymsg bar height 50

or

    swaymsg bar not-a-bar-id color bg #ff0000

This was in contrast to other bar subcommands, like status_command,
which would exit with a "No bar defined" message.

The difference between the subcommands that crashed and the ones that
exited was that some subcommands had a check to see if a bar was
specified, while others just assumed that it had been and carried on
until they segfaulted.

Because this check was identical in every subcommand it was present in,
and I couldn't think of a case where it would be valid to run a bar
subcommand without specifying which bar to apply it to, I moved this
check from individual subcommands into the bar command, which is already
responsible for actually setting the specified bar. This reduced code
duplication, and fixed the crash for the subcommands that were missing
this check.

1 files changed, 21 insertions, 17 deletions

diff --git a/sway/commands/bar.c b/sway/commands/bar.c
index 73be7040..9c7357dd 100644
--- a/sway/commands/bar.c
+++ b/sway/commands/bar.c
@@ -82,26 +82,30 @@ struct cmd_results *cmd_bar(int argc, char **argv) {
                 ++argv; --argc;
         }
 
-        if (!config->current_bar && config->reading) {
-                // Create new bar with default values
-                struct bar_config *bar = default_bar_config();
-                if (!bar) {
-                        return cmd_results_new(CMD_FAILURE,
-                                        "Unable to allocate bar state");
-                }
+        if (!config->current_bar) {
+                if (config->reading) {
+                        // Create new bar with default values
+                        struct bar_config *bar = default_bar_config();
+                        if (!bar) {
+                                return cmd_results_new(CMD_FAILURE,
+                                                "Unable to allocate bar state");
+                        }
+
+                        // set bar id
+                        int len = snprintf(NULL, 0, "bar-%d", config->bars->length - 1) + 1;
+                        bar->id = malloc(len * sizeof(char));
+                        if (bar->id) {
+                                snprintf(bar->id, len, "bar-%d", config->bars->length - 1);
+                        } else {
+                                return cmd_results_new(CMD_FAILURE, "Unable to allocate bar ID");
+                        }
 
-                // set bar id
-                const int len = snprintf(NULL, 0, "bar-%d", config->bars->length - 1) + 1;
-                bar->id = malloc(len * sizeof(char));
-                if (bar->id) {
-                        snprintf(bar->id, len, "bar-%d", config->bars->length - 1);
+                        // Set current bar
+                        config->current_bar = bar;
+                        sway_log(SWAY_DEBUG, "Creating bar %s", bar->id);
                 } else {
-                        return cmd_results_new(CMD_FAILURE, "Unable to allocate bar ID");
+                        return cmd_results_new(CMD_FAILURE, "No bar defined.");
                 }
-
-                // Set current bar
-                config->current_bar = bar;
-                sway_log(SWAY_DEBUG, "Creating bar %s", bar->id);
         }
 
         if (find_handler(argv[0], bar_config_handlers,