How to use long_version command attribute with LazyCell?

[cylewitruk]

Hi there,

I've got a version string being created in a LazyCell:

const VERSION_STRING: LazyCell<String> = LazyCell::new(|| {
    let pkg_version = option_env!("STACKS_NODE_VERSION").unwrap_or(env!("CARGO_PKG_VERSION"));
    let git_branch = GIT_BRANCH.unwrap_or("");
    let git_commit = GIT_COMMIT.unwrap_or("");
    format!(
        "{} ({}:{}, {} build, {} [{}])",
        pkg_version,
        git_branch,
        git_commit,
        BUILD_TYPE,
        std::env::consts::OS,
        std::env::consts::ARCH
    )
});

When trying to use this in the command attribute:

#[command(long_version = *VERSION_STRING)]

I get the error:

69   | #[command(long_version = *VERSION_STRING)]
     |           ------------   ^^^^^^^^^^^^^^^ the trait `From<std::string::String>` is not implemented for `clap::builder::Str`, which is required by `std::string::String: IntoResettable<clap::builder::Str>`

Feels weird that I can't provide a String here? I've tried various methods to get this to a &str, but then I run into problems with the borrow checker.

Any ideas?

[epage]

There should be a way to get a &'static str from that LazyCell<String>; we use OnceLock<String> in clap_derive

See

clap/clap_derive/src/item.rs

Lines 577 to 585 in edcaf8f

	quote_spanned!(attr.name.span()=> {
	static DEFAULT_VALUE: ::std::sync::OnceLock<String> = ::std::sync::OnceLock::new();
	let s = DEFAULT_VALUE.get_or_init(|| {
	let val: #ty = #val;
	clap::ValueEnum::to_possible_value(&val).unwrap().get_name().to_owned()
	});
	let s: &'static str = &*s;
	s
	})

[cylewitruk]

Yeah I've tried coercing as well, but keep ending up with creates a temporary value which is freed while still in use no matter which way I turn it... I'll take this question over to discord and see if anyone has some ideas, this worked with lazy_static! (switching to LazyCell), so I'm sure there's a way that I just haven't thought of yet...

[cylewitruk]

The solution was to use static instead of const, and LazyLock instead of LazyCell :) Then I could simply &* it.