Establish CARGO_MANIFEST_DIR
#180
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To be clear, libraries that use this need to declare whatever additional files as data dependencies, and then everything Just Works? |
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Thanks for the PR! I'm refreshed to hear that one of my large comments was used to produce a fix!
I think I'd like to see an example or test added for this -- if only to guarantee to later readers that the feature worked in this PR. I can understand if that might be onerous.... chiefly in having to either vendor deps for Pest, or produce a minimum example from Pest's source. I happen to prefer the second option if no other presents itself.
See google/cargo-raze#71 (comment) for the rationale as to why In brief: Certain rust build processes expect to find files from the environment variable `$CARGO_MANIFEST_DIR`. Examples of this include pest, tera, asakuma. The compiler and by extension proc-macros see the current working directory as the Bazel exec root. Therefore, in order to fix this without an upstream code change, we have to set `$CARGO_MANIFEST_DIR`. As such we attempt to infer `$CARGO_MANIFEST_DIR`. Inference cannot be derived from `attr.crate_root`, as this points at a source file which may or may not follow the `src/lib.rs` convention. As such we use `ctx.build_file_path` mapped into the `exec_root`. Since we cannot (seemingly) get the `exec_root` from skylark, we cheat a little and use `$(pwd)` which resolves the `exec_root` at action execution time. Fixes: google/cargo-raze#71
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@mfarrugi Yes, @acmcarther rather than vendor pest, which would only work for this snapshot / point in time, would a simple rust file that uses I think for pest / tera maybe we should add a test over in cargo-raze as a smoke test too? Thoughts? |
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@acmcarther ... in fact if anything maybe with this we could solve google/cargo-raze#61 which would also function as a fairly solid test |
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I think the test added here is sufficient (not sure if it was added before or after the comment). @acmcarther wdyt? |
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@mfarrugi added after for your reference. |
Several popular crates, as well as some source code has a habit of using
env!("CARGO_MANIFEST_DIR")to find files in a crate. This causes things like google/cargo-raze#71.Following @acmcarther suggestions this is an attempt at solution 3, which appears to handle (ab)uses of
CARGO_MANIFEST_DIRI have tested (tera, askuma).