Fix panic on x build --help --verbose

This also makes the panic message a little more informative in case it
happens again.

src/bootstrap/flags.rs

@@ -351,7 +351,17 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
 
  // fn usage()
  let usage = |exit_code: i32, opts: &Options, verbose: bool, subcommand_help: &str| -> ! {
- let config = Config::parse(&["setup".to_string()]);
+ // We have an unfortunate situation here: some Steps use `builder.in_tree_crates` to determine their paths.
+ // To determine those crates, we need to run `cargo metadata`, which means we need all submodules to be checked out.
+ // That takes a while to run, so only do it when paths were explicitly requested, not on all CLI errors.
+ // `Build::new` won't load submodules for the `setup` command.
+ let cmd = if verbose {
+ println!("note: updating submodules before printing available paths");
+ "build"
+ } else {
+ "setup"
+ };
+ let config = Config::parse(&[cmd.to_string()]);
  let build = Build::new(config);
  let paths = Builder::get_help(&build, subcommand);
 

src/bootstrap/lib.rs

@@ -1400,7 +1400,10 @@ impl Build {
  let mut list = vec![INTERNER.intern_str(root)];
  let mut visited = HashSet::new();
  while let Some(krate) = list.pop() {
- let krate = &self.crates[&krate];
+ let krate = self
+ .crates
+ .get(&krate)
+ .unwrap_or_else(|| panic!("metadata missing for {krate}: {:?}", self.crates));
  ret.push(krate);
  for dep in &krate.deps {
  if !self.crates.contains_key(dep) {