[WIP] feat: Multiple build scripts #15630

namanlp · 2025-06-04T20:37:25Z

Hi Everyone!

This is PR for 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.

How to test and review this PR?

There is a feature gate multiple-build-scripts that can be passed with -Z in cargo.

It is not ready for review yet

epage · 2025-06-04T20:50:23Z

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

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

epage · 2025-06-09T16:26:14Z

src/cargo/core/features.rs

@@ -1361,6 +1362,7 @@ impl CliUnstable {
            "msrv-policy" => self.msrv_policy = parse_empty(k, v)?,
            // can also be set in .cargo/config or with and ENV
            "mtime-on-use" => self.mtime_on_use = parse_empty(k, v)?,
+            "multiple-build-scripts" => self.multiple_build_scripts = parse_empty(k, v)?,


This commit should also add a section for this to our unstable docs. There isn't much to say but we should add more to it as features get implemented.

epage · 2025-06-09T16:29:01Z

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

+            TomlPackageBuild::MultipleScript(_scripts) => {
+                unimplemented!("Multiple Build Scripts feature is not implemented yet!")
+            }
        }


In a commit before this one, we should update normalized_build to return Result<Option<&Vec<String>>, UnresolvedError> to avoid this unimplemented!

epage · 2025-06-09T16:31:12Z

src/cargo/ops/vendor.rs

+    match &package.build {
+        Some(TomlPackageBuild::SingleScript(path)) => {
+            let path = paths::normalize_path(Path::new(path));
+            let included = packaged_files.contains(&path);
+            let build = if included {
+                let path = path
+                    .into_os_string()
+                    .into_string()
+                    .map_err(|_err| anyhow::format_err!("non-UTF8 `package.build`"))?;
+                let path = crate::util::toml::normalize_path_string_sep(path);
+                TomlPackageBuild::SingleScript(path)
+            } else {
+                gctx.shell().warn(format!(
+                    "ignoring `package.build` as `{}` is not included in the published package",
+                    path.display()
+                ))?;
+                TomlPackageBuild::Auto(false)
+            };
+            package.build = Some(build);
+        }
+        Some(TomlPackageBuild::MultipleScript(_scripts)) => {
+            if gctx.cli_unstable().multiple_build_scripts {
+                unimplemented!("Multiple build script is not implemented yet!");
+            } else {
+                bail!("`build = […]` requires `-Z multiple-build-scripts`");
+            }
+        }


I'd recommend unifying this code so there is a single code path for single or multiple scripts.

Maybe something like https://doc.rust-lang.org/std/option/enum.Option.html#method.as_slice could help

epage · 2025-06-09T16:32:19Z

src/cargo/util/toml/mod.rs

+    let multiple_build_scripts = gctx.cli_unstable().multiple_build_scripts;
    let build = if is_embedded {
        Some(TomlPackageBuild::Auto(false))
    } else {
-        targets::normalize_build(original_package.build.as_ref(), package_root)
+        targets::normalize_build(


"the hackiest hack is the best hack"
or
"when implementing short-lived or hacky code, be as surgical as possible"

I'd recommend we do the unstable check here, rather than updating normalize_builds API to take in a parameter related to this

epage · 2025-06-09T16:32:46Z

src/cargo/core/features.rs

@@ -840,6 +840,7 @@ unstable_cli_options!(
    minimal_versions: bool = ("Resolve minimal dependency versions instead of maximum"),
    msrv_policy: bool = ("Enable rust-version aware policy within cargo"),
    mtime_on_use: bool = ("Configure Cargo to update the mtime of used files"),
+    multiple_build_scripts: bool = ("Enables the use of multiple build scripts"),


I overlooked this before, this was implemented as a -Z when this needs to be a cargo_features.

Ok, replaced it with cargo_features

epage · 2025-06-09T16:33:28Z

src/cargo/util/toml/mod.rs

    // Validates if build script file exists. If not, warn and ignore.
-    if let Some(TomlPackageBuild::SingleScript(path)) = &package.build {
-        let path = Path::new(path).to_path_buf();
-        let included = packaged_files.map(|i| i.contains(&path)).unwrap_or(true);
-        let build = if included {
-            let path = path
-                .into_os_string()
-                .into_string()
-                .map_err(|_err| anyhow::format_err!("non-UTF8 `package.build`"))?;
-            let path = normalize_path_string_sep(path);
-            TomlPackageBuild::SingleScript(path)
-        } else {
-            ws.gctx().shell().warn(format!(
-                "ignoring `package.build` as `{}` is not included in the published package",
-                path.display()
-            ))?;
-            TomlPackageBuild::Auto(false)
-        };
-        package.build = Some(build);
+    match &package.build {


ditto what I said with vendor

epage · 2025-06-09T16:34:02Z

src/cargo/util/toml/targets.rs

+        }
+        Some(TomlPackageBuild::MultipleScript(_scripts)) => {
+            if multiple_build_scripts {
+                unimplemented!("Multiple Build Scripts feature is not implemented yet!");


Let's go ahead and do this in this commit

Also, I'd like to see runtime errors, rather than panics for when we cut users off from this feature.

…schema.json

…ed on nightly)

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

View reviewed changes

crates/cargo-util-schemas/src/manifest/mod.rs Outdated Show resolved Hide resolved

epage reviewed Jun 5, 2025

View reviewed changes

crates/cargo-util-schemas/src/manifest/mod.rs Outdated Show resolved Hide resolved

epage reviewed Jun 5, 2025

View reviewed changes

crates/cargo-util-schemas/src/manifest/mod.rs Outdated Show resolved Hide resolved

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

Rename readme variable to build

5e0f239

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

epage reviewed Jun 9, 2025

View reviewed changes

namanlp force-pushed the multiple-build-scripts-1 branch from 0321144 to 6de78d5 Compare June 10, 2025 22:39

rustbot added the A-documenting-cargo-itself Area: Cargo's documentation label Jun 10, 2025

namanlp added 3 commits June 11, 2025 04:12

Add feature gate for multiple build scripts

2c403a8

Fork StringOrBool into new TomlPackageBuild type and update manifest.…

0ff33ed

…schema.json

Add Multiple Build Script (error on stable, error about not implement…

158dd35

…ed on nightly)

namanlp force-pushed the multiple-build-scripts-1 branch from 6de78d5 to 158dd35 Compare June 10, 2025 22:43

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

[WIP] feat: Multiple build scripts #15630

[WIP] feat: Multiple build scripts #15630

Uh oh!

namanlp commented Jun 4, 2025

Uh oh!

epage commented Jun 4, 2025

Uh oh!

Uh oh!

Uh oh!

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

namanlp Jun 10, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

epage Jun 9, 2025

Uh oh!

Uh oh!

[WIP] feat: Multiple build scripts #15630

Are you sure you want to change the base?

[WIP] feat: Multiple build scripts #15630

Uh oh!

Conversation

namanlp commented Jun 4, 2025

What does this PR try to resolve?

How to test and review this PR?

Uh oh!

epage commented Jun 4, 2025

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!