Added build.build-dir support

[ranger-ross]

This PR adds build_dir to the BuildConfig

See: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-dir

closes #28

[taiki-e]

Thanks! The implementation looks good.

However, given that this is an unstable feature and could lead to errors if the accepted syntax changes in the future, it might be better to put it behind a feature flag.

[ranger-ross]

Sure, perhaps we add a generic unstable flag similar to cargo_metadata

[taiki-e]

That sounds like a good idea.

I'm usually against using the Cargo feature for unstable stuff (rust-lang/api-guidelines#284 (comment)), but in this case I think the Cargo feature will be fine since the only users affected are those who explicitly use the unstable feature in their config files.

[ranger-ross]

I added an unstable feature flag and support for it in tools/codegen.
let me know what you think :)

[taiki-e]

Thanks. That looks good to me.

I looked at the documentation again and it looks like the environment variable is supported, so could you update src/env.rs to handle that?

https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#build-dir

Environment: CARGO_BUILD_BUILD_DIR

[ranger-ross]

Added CARGO_BUILD_BUILD_DIR handling in the latest push.

Regarding the failing CI jobs, seems unrelated.

Preparing a careful sysroot (target: x86_64-unknown-linux-gnu)... thread 'main' panicked at src/main.rs:267:10:
failed to build sysroot; run `cargo careful setup` to see what went wrong: sysroot build failed

I pulled the latest nightly and ran cargo +nightly careful test --all --all-features on my machine and could not reproduce a failure.

[taiki-e]

Hmm... given the presence of templates, I wonder if there is a problem with unconditional invocation of resolve_as_path here.

Cargo Reference says:

This option supports path templating.

Available template variables:

• {workspace-root} resolves to root of the current workspace.
• {cargo-cache-home} resolves to CARGO_HOME
• {workspace-path-hash} resolves to a hash of the manifest path

Perhaps resolve_as_path should be skipped if the path starts with {workspace-root} or {cargo-cache-home}.

Also, it would be nice to mention in the documentation that these templates are not resolved.

[ranger-ross]

yes, agreed.
Added handling for that in the latest commit.

[taiki-e]

I don't think we need to care about {workspace-path-hash} since it doesn't resolve to an absolute path.

[ranger-ross]

thanks, removed!

[taiki-e]

Could you address the review (#29 (review)) and remove the unstable stuff (since build-dir is now stabilized)?

[ranger-ross]

Sorry for the late follow up on this!

Addressed your comment and pushed another commit to stabilize build-dir.
I left the unstable feature machinery for future use, though I can remove it you'd prefer.

[taiki-e]

Thanks!

[taiki-e]

Published in 0.1.37.