Add the CARGO_CRATE_NAME env var

[arlyon]

See #536 for more discussion.

[illicitonion]

Thanks for the contribution! I agree that we should set this env var, but I think we should maybe set it to a slightly different value - let me know what you think :)

To see cargo's behaviour:

$ cargo init crate-with-dashes
$ cd crate-with-dashes
$ cat >src/main.rs <<EOF
fn main() {
    println!("CARGO_CRATE_NAME: {}", env!("CARGO_CRATE_NAME"));
    println!("CARGO_PKG_NAME: {}", env!("CARGO_PKG_NAME"));
}
EOF
$ cargo run --quiet
CARGO_CRATE_NAME: crate_with_dashes
CARGO_PKG_NAME: crate-with-dashes

[illicitonion]

Sorry for the delay!

Unfortunately this PR now goes the wrong way around: CARGO_PKG_NAME should always be set based on the name attribute, and crate_name should replace -s with _s. The CARGO_PKG_NAME may contain _s, whereas right now this PR replaces all _s with -.

[hlopko]

Friendly ping from a bywalker :)

[arlyon]

Thanks for the ping, this fell of my todo list :) I will push changes asap. Am I right in saying that 'crate_name' in rules rust actually refers to the pkg name then? ie. rules_rust uses the name an Cargo.toml rather than the name in code.

It feels inconsistent so I want to get it right:

ctx.attr.crate_name == "my-cool_crate"

pkg_name = ctx.attr.crate_name
crate_name = pkg_name.replace("_", "-")

pkg_name == "my-cool_crate"
crate_name == "my_cool_crate"

[UebelAndre]

Friendly drive-by ping, any updates here? 😄

[arlyon]

We're not far off, but if the crate name in rules_rust is in fact the pkg_name then that differenciation should be reflected in the properties in the attributes and we should rename it. I'm not sure about the implications of this though so some feedback would be helpful.

[illicitonion]

We're not far off, but if the crate name in rules_rust is in fact the pkg_name then that differenciation should be reflected in the properties in the attributes and we should rename it. I'm not sure about the implications of this though so some feedback would be helpful.

That's a really good point! And I think we can answer it with my favourite answer of all: Let's delete the attribute!

As far as I can tell, we currently use the crate_name attribute in exactly three places:

1. We use it to set CARGO_PKG_NAME
2. We uppercase it and replace -s with _s to set CARGO_FEATURE_${CRATE_NAME}=1 env vars per feature
3. We use it for some legacy fallback behaviour to guess what the links attribute should've been before we had the links attribute - Set links attribute google/cargo-raze#400 will allow us to delete the fallback behaviour.

(Worthy of note, we don't use it for the thing it was originally added for in #341, which was to set DEP_ env vars, they now use the links attribute, except where that fallback is used).

So I'd be tempted to delete the crate_name attribute entirely, and just treat the name attribute like the thing we'd see in a package.name of a Cargo.toml. If we did that, we'd (after removing a trailing _build_script if present) set CARGO_PKG_NAME to exactly ctx.attr.name, set CARGO_CRATE_NAME to the -s to _s version, set CARGO_FEATURE_${CRATE_NAME} using the uppercased version of CARGO_CRATE_NAME, and have removed an unnecessary attribute on the way.

[hlopko]

SGTM, I'm a big fan of deleting and simplifying code, let's do this!

[arlyon]

Closing after a more comprehensive solution here #643 thanks all!