feat(toml): Parse support for multiple build scripts #15630

namanlp · 2025-06-04T20:37:25Z

Hi Everyone!

This is PR for the manifest parsing of the first milestone of GSoC Project : Build Script Delegation

What does this PR try to resolve?

Currently, just a single build script is allowed for each package. This PR will allow users to create and use multiple build scripts, and is backward compatible with single script as well as boolean values.

Motivation : This will help users to maintain separate smaller and cleaner build scripts instead of one large build script. This is also necessary for build script delegation.

Open questions:

What should the build script target names be?
- Currently they use the file stem of the build script which could run into conflicts

Known Issues:

This is just parsing support, and currently, only the first build script of the array is actually executed.

How to test and review this PR?

There is a feature gate multiple-build-scripts that can be passed via cargo-features in Cargo.toml. So, you have to add

cargo-features = ["multiple-build-scripts"]

Preferably on the top of the Cargo.toml and use nightly toolchain to use the feature

This PR is ready to be reviewed and merged

epage · 2025-06-04T20:50:23Z

Feel free to rebase on master, rather than merge it.

crates/cargo-util-schemas/src/manifest/mod.rs

src/cargo/core/features.rs

crates/cargo-util-schemas/src/manifest/mod.rs

src/cargo/ops/vendor.rs

src/cargo/util/toml/mod.rs

src/cargo/core/features.rs

src/cargo/util/toml/mod.rs

src/cargo/util/toml/targets.rs

epage · 2025-06-12T20:04:22Z

src/cargo/util/toml/targets.rs

+        if custom_build.len() > 1 {
+            anyhow::bail!("multiple build scripts feature is not implemented yet! ")
+        }
+        let custom_build = Path::new(&custom_build[0]);
        let name = format!(
            "build-script-{}",
            custom_build


We'll need to loop over

Do we need to make build script names more unique?

src/doc/src/reference/unstable.md

…schema.json

… nightly)

epage · 2025-06-23T14:28:45Z

Thanks!

Update cargo 2 commits in 84709f085062cbf3c51fa507527c1b2334015178..409fed7dc1553d49cb9a8c0637d12d65571346ce 2025-06-22 23:58:39 +0000 to 2025-06-23 15:55:04 +0000 - Fix potential deadlock in `CacheState::lock` (rust-lang/cargo#15698) - feat(toml): Parse support for multiple build scripts (rust-lang/cargo#15630)

Rollup merge of #142993 - ehuss:update-cargo, r=ehuss Update cargo 2 commits in 84709f085062cbf3c51fa507527c1b2334015178..409fed7dc1553d49cb9a8c0637d12d65571346ce 2025-06-22 23:58:39 +0000 to 2025-06-23 15:55:04 +0000 - Fix potential deadlock in `CacheState::lock` (rust-lang/cargo#15698) - feat(toml): Parse support for multiple build scripts (rust-lang/cargo#15630)

Hi Everyone! This is PR for the implementation of the first milestone of [GSoC Project : Build Script Delegation](https://summerofcode.withgoogle.com/programs/2025/projects/nUt4PdAA) This will provide actual implementation for #15630 ### What does this PR try to resolve? Now, multiple build scripts are parsed, this PR aims to implement the functioning the feature. This PR will allow users to use multiple build scripts, and is backward compatible with single script as well as boolean values. **Motivation :** This will help users to maintain separate smaller and cleaner build scripts instead of one large build script. This is also necessary for build script delegation. Deferred - Accessing each build script's `OUT_DIR`: This will be handled in a follow up PR. For now, each build script writes to its own `OUT_DIR` and `OUT_DIR` for the regular build targets is set to the build script with the **lexicographically largest** name.. - User control over which build script wins in a conflict. This will be handled in a follow up PR. If two build scripts write to the same env variable, which gets applied to the binary? Currently, its the build script with the **lexicographically largest** name. This makes it deterministic. With some futzing, users can control this for now. However, with build script delegation, users won't be able to control this. We likely want it based off of the order the user assigns into the build script array. - Something about linking a C library is actually preferring **lexicographically smallest** name. We should handle conflicts consistently. We need to dig into what parts are doing it based on smallest and make sure that whatever priority scheme we use for env variables applies here as well. ### How to test and review this PR? There is a feature gate `multiple-build-scripts` that can be passed via `cargo-features` in `Cargo.toml`. So, you have to add ```toml cargo-features = ["multiple-build-scripts"] ``` Preferably on the top of the `Cargo.toml` and use nightly toolchain to use the feature

rustbot added the A-unstable Area: nightly unstable support label Jun 4, 2025

rustbot added A-manifest Area: Cargo.toml issues Command-vendor labels Jun 5, 2025

epage reviewed Jun 5, 2025

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epage reviewed Jun 5, 2025

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namanlp closed this Jun 6, 2025

namanlp force-pushed the multiple-build-scripts-1 branch from 60fe887 to f6bebc3 Compare June 6, 2025 21:16

namanlp reopened this Jun 6, 2025

namanlp force-pushed the multiple-build-scripts-1 branch 2 times, most recently from b7a6036 to 1d18b6b Compare June 8, 2025 22:09