A cargo subcommand to fetch the $OUT_DIR environment variable from build scripts

Last update: Sep 29, 2022

Related tags

Learning Resources cargo-outdir

Overview

cargo-outdir

A cargo subcommand to fetch the $OUT_DIR variable from build scripts.

This is extremely useful to inspect the output of automatically generated code, like bindgen or parol.

This can be seen as an extension to cargo metadata, except it requires that cargo check succeeds.

If cargo check succeeds, then this command succeeds too (and give the same output).

Due to recent changes in cargo check, this will not invalidate cached outputs, so the build scripts wont be re-run unless they need to :)

It is effectively a workaround to rust-lang/cargo#7546

Examples

`$ cargo out`

Assuming your current crate is named current-crate, this wil output something like:

current-crate /Users/techcable/git/current-crate/target/debug/build/current-crate-82e5bb1cb82b68a7/out

Alternatively, to omit the name you can use --no-names. This is useful in shell scripts as $(cargo out --no-names)

This command works with any crate name (as long as it has a build.rs file).

`$ cargo out syn indexmap`

syn /Users/techcable/git/current-crate/target/debug/build/syn-2bbc24a01fc81726/out
indexmap /Users/techcable/git/current-crate/target/debug/build/indexmap-376e9f234cf30ee8/out

These are output in the order specified on the command line, seperated by newlines.

If the package doesn't have an out dir, the output will be "" exactly and the exit code will be 2.

You might want to consider json output as well.

`$ cargo out --json --all`

{
    "syn": "/Users/techcable/git/current-crate/target/debug/build/syn-2bbc24a01fc81726/out",
    "indexmap": "/Users/techcable/git/current-crate/target/debug/build/indexmap-376e9f234cf30ee8/out",
    "libc:0.1.12": null,
    "libc:0.2.109": "/Users/techcable/git/current-crate/target/debug/build/libc-1c95e0902b980b08/out",
    // other_crates here
}

If packages don't have an $OUT_DIR (because they don't have a build script), then the value for the specified key will be null.

This can be used along with jq for easy processing in scripts :)

If multiple packages have the same name, then version will be added. More precicely, the json keys will be the minimal cargo pkgid needed to disambiguate them. This is actually somewhat difficult to do :)

How it works

This runs cargo check --message-format=json and extracts only the nessicarry information.

Historically this has been an issue for IDEs, both intellij-rust and rust-analsyer have struggled to support this.

Do to recent compiler changes, this will always output the proper $OUT_DIR variables for all packages that have one.

However recent changes to cargo check have made this possible. It sill :)

TypeRust - simple Rust playground where you can build or run your Rust code and share it with others

Rust playground Welcome to TypeRust! This is a simple Rust playground where you can build or run your Rust code and share it with others. There are a

28 Dec 12, 2022

Automated license checking for rust. cargo lichking is a Cargo subcommand that checks licensing information for dependencies.

cargo-lichking Automated license checking for rust. cargo lichking is a Cargo subcommand that checks licensing information for dependencies. Liches ar

120 Dec 19, 2022

cargo-lambda a Cargo subcommand to help you work with AWS Lambda

cargo-lambda cargo-lambda is a Cargo subcommand to help you work with AWS Lambda. This subcommand compiles AWS Lambda functions natively and produces

184 Jan 5, 2023

cargo-lambda is a Cargo subcommand to help you work with AWS Lambda.

cargo-lambda cargo-lambda is a Cargo subcommand to help you work with AWS Lambda. The new subcommand creates a basic Rust package from a well defined

184 Jan 5, 2023

Cargo subcommand for running cargo without dev-dependencies.

cargo-no-dev-deps Cargo subcommand for running cargo without dev-dependencies. This is an extraction of the --no-dev-deps flag of cargo-hack to be use

5 Jan 12, 2023

A cargo subcommand that extends cargo's capabilities when it comes to code generation.

cargo-px Cargo Power eXtensions Check out the announcement post to learn more about cargo-px and the problems it solves with respect to code generatio

33 May 7, 2023

Dead simple, memoized cargo subcommand to hoist cargo-built binaries into the current working directory, written in Rust.

cargo-hoist Dead simple cargo subcommand to hoist cargo-built binaries into scope. stable Install | User Docs | Crate Docs | Reference | Contributing

6 Nov 9, 2023

A tool that uses the credentials stored in 1password as an environment variable.

openv A tool that uses the credentials stored in 1password as an environment variable. Requirements 1password command-line tool Getting Started # Sign

31 Nov 10, 2022

FlatBuffers compiler (flatc) as API (with focus on transparent `.fbs` to `.rs` code-generation via Cargo build scripts integration)

FlatBuffers flatc API for Rust This crate provides a programmatical way to invoke flatc command (e.g. from build.rs) to generate Rust (or, in fact, an