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Merged
epage merged 5 commits into from
Aug 3, 2026
Merged

fix(trim-paths): unambiguous and reversible remap rules #17302

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c0102f5
refactor(trim-paths): extract remap into own module
weihanglo Jul 31, 2026
39a2f56
test(trim-paths): build-script remap with local package
weihanglo Jul 31, 2026
bf4a306
test(trim-paths): cover vendored dependencies
weihanglo Jul 31, 2026
5b3974e
fix(trim-paths): unambiguous and reversible remap rules
weihanglo Jul 31, 2026
2a8b6fd
docs(trim-paths): unambiguous and reversible remap rules
weihanglo Jul 31, 2026
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27 changes: 24 additions & 3 deletions doc/book/src/reference/unstable.md
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Original file line number Diff line number Diff line change
Expand Up @@ -1549,11 +1549,32 @@ But the paths to these separate files are sanitized.

If `trim-paths` is not `none` or `false`, then the following paths are sanitized if they appear in a selected scope:

1. Path to the source files of the standard and core library (sysroot) will begin with `/rustc/[rustc commit hash]`,
1. Path to the source files of the standard and core library (sysroot) will begin with `/rustc/<rustc commit hash>`,
e.g. `/home/username/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/result.rs` ->
`/rustc/fe72845f7bb6a77b9e671e6a4f32fe714962cec4/library/core/src/result.rs`
2. Path to the current package will be stripped, relatively to the current workspace root, e.g. `/home/username/crate/src/lib.rs` -> `src/lib.rs`.
3. Path to dependency packages will be replaced with `[package name]-[version]`. E.g. `/home/username/deps/foo/src/lib.rs` -> `foo-0.1.0/src/lib.rs`
2. Path to the current package will be stripped,
relatively to the current workspace root,
e.g. `/home/username/crate/src/lib.rs` -> `src/lib.rs`.
This also covers path dependencies located inside the workspace directory.
3. Path to a registry dependency will begin with `/cargo/registry/<registry id>`,
which replaces the registry's extraction directory,
e.g. `/home/username/.cargo/registry/src/index.crates.io-6f17d22d3f0a95d1/foo-0.1.0/src/lib.rs` ->
`/cargo/registry/6f17d22d3f0a95d1/foo-0.1.0/src/lib.rs`.
4. Path to a git dependency will begin with `/cargo/git/<git source id>/<revision>`,
which replaces the checkout directory.
`<revision>` is a prefix of the resolved commit ID recorded in the lockfile.
5. Path to a path dependency outside the workspace will be replaced with
`/cargo/path/<package name>-<package version>`.
6. Path into the build directory, for example `OUT_DIR` generated sources,
will begin with `/cargo/build-dir`.

`<registry id>` and `<git source id>` are opaque stable hashes of the dependency's source.

Vendored copies of registry or git dependencies
(via [source replacement](./source-replacement.md))
are sanitized by their file location instead,
like workspace paths when inside the workspace directory,
otherwise like path dependencies.

When a path to the source files of the standard and core library is *not* in scope for sanitization,
the emitted path will depend on if `rust-src` component is present.
Expand Down
2 changes: 1 addition & 1 deletion src/compiler/custom_build.rs
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Expand Up @@ -403,7 +403,7 @@ fn build_work(build_runner: &mut BuildRunner<'_, '_>, unit: &Unit) -> CargoResul
if let Some(trim_paths) = unit.profile.trim_paths.as_ref() {
cmd.env("CARGO_TRIM_PATHS_SCOPE", trim_paths.to_string());
if !trim_paths.is_none() {
let pairs = super::trim_paths_remap(build_runner, unit);
let pairs = super::trim_paths::trim_paths_remap(build_runner, unit);
cmd.env(
"CARGO_TRIM_PATHS_REMAP",
paths::join_paths(&pairs, "CARGO_TRIM_PATHS_REMAP")?,
Expand Down
158 changes: 3 additions & 155 deletions src/compiler/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,7 @@ mod output_sbom;
pub mod rustdoc;
pub mod standard_lib;
pub mod timings;
mod trim_paths;
mod unit;
pub mod unit_dependencies;
pub mod unit_graph;
Expand Down Expand Up @@ -95,6 +96,8 @@ pub(crate) use self::layout::Layout;
pub use self::lto::Lto;
use self::output_depinfo::output_depinfo;
use self::output_sbom::build_sbom;
use self::trim_paths::trim_paths_args;
use self::trim_paths::trim_paths_args_rustdoc;
use self::unit_graph::UnitDep;

use crate::compiler::future_incompat::FutureIncompatReport;
Expand All @@ -115,8 +118,6 @@ use crate::workspace::{Feature, PackageId, Target};

use cargo_util::{ProcessBuilder, ProcessError, paths};
use cargo_util_schemas::manifest::TomlDebugInfo;
use cargo_util_schemas::manifest::TomlTrimPaths;
use cargo_util_schemas::manifest::TomlTrimPathsValue;
use cargo_util_terminal::Verbosity;
use rustfix::diagnostics::Applicability;

Expand Down Expand Up @@ -1525,159 +1526,6 @@ fn features_args(unit: &Unit) -> Vec<OsString> {
args
}

/// Like [`trim_paths_args`] but for rustdoc invocations.
fn trim_paths_args_rustdoc(
cmd: &mut ProcessBuilder,
build_runner: &BuildRunner<'_, '_>,
unit: &Unit,
trim_paths: &TomlTrimPaths,
) -> CargoResult<()> {
match trim_paths {
// rustdoc supports diagnostics trimming only.
TomlTrimPaths::Values(values) if !values.contains(&TomlTrimPathsValue::Diagnostics) => {
return Ok(());
}
_ => {}
}

for pair in trim_paths_remap(build_runner, unit) {
let mut arg = OsString::from("--remap-path-prefix=");
arg.push(pair);
cmd.arg(arg);
}

Ok(())
}

/// Generates the `--remap-path-scope` and `--remap-path-prefix` for [RFC 3127].
/// See also unstable feature [`-Ztrim-paths`].
///
/// [RFC 3127]: https://rust-lang.github.io/rfcs/3127-trim-paths.html
/// [`-Ztrim-paths`]: https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#profile-trim-paths-option
fn trim_paths_args(
cmd: &mut ProcessBuilder,
build_runner: &BuildRunner<'_, '_>,
unit: &Unit,
trim_paths: &TomlTrimPaths,
) -> CargoResult<()> {
if trim_paths.is_none() {
return Ok(());
}

// feature gate was checked during manifest/config parsing.
cmd.arg(format!("--remap-path-scope={trim_paths}"));

for pair in trim_paths_remap(build_runner, unit) {
let mut arg = OsString::from("--remap-path-prefix=");
arg.push(pair);
cmd.arg(arg);
}

Ok(())
}

/// Computes the `<from>=<to>` path remap pairs for [RFC 3127] trim-paths.
///
/// Order of `--remap-path-prefix` flags is important for `-Zbuild-std`.
/// We want to show `/rustc/<hash>/library/std` instead of `std-0.0.0`.
///
/// [RFC 3127]: https://rust-lang.github.io/rfcs/3127-trim-paths.html
pub(crate) fn trim_paths_remap(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> [OsString; 3] {
[
package_remap(build_runner, unit),
build_dir_remap(build_runner),
sysroot_remap(build_runner, unit),
]
}

/// Path prefix remap rules for sysroot.
///
/// This remap logic aligns with rustc:
/// <https://github.com/rust-lang/rust/blob/c2ef3516/src/bootstrap/src/lib.rs#L1113-L1116>
fn sysroot_remap(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> OsString {
let mut remap = OsString::new();
remap.push({
// See also `detect_sysroot_src_path()`.
let mut sysroot = build_runner.bcx.target_data.info(unit.kind).sysroot.clone();
sysroot.push("lib");
sysroot.push("rustlib");
sysroot.push("src");
sysroot.push("rust");
sysroot
});
remap.push("=");
remap.push("/rustc/");
if let Some(commit_hash) = build_runner.bcx.rustc().commit_hash.as_ref() {
remap.push(commit_hash);
} else {
remap.push(build_runner.bcx.rustc().version.to_string());
}
remap
}

/// Path prefix remap rules for dependencies.
///
/// * Git dependencies: remove `~/.cargo/git/checkouts` prefix.
/// * Registry dependencies: remove `~/.cargo/registry/src` prefix.
/// * Others (e.g. path dependencies):
/// * relative paths to workspace root if inside the workspace directory.
/// * otherwise remapped to `<pkg>-<version>`.
fn package_remap(build_runner: &BuildRunner<'_, '_>, unit: &Unit) -> OsString {
let pkg_root = unit.pkg.root();
let ws_root = build_runner.bcx.ws.root();
let mut remap = OsString::new();
let source_id = unit.pkg.package_id().source_id();
if source_id.is_git() {
remap.push(
build_runner
.bcx
.gctx
.git_checkouts_path()
.as_path_unlocked(),
);
remap.push("=");
} else if source_id.is_registry() {
remap.push(
build_runner
.bcx
.gctx
.registry_source_path()
.as_path_unlocked(),
);
remap.push("=");
} else if pkg_root.strip_prefix(ws_root).is_ok() {
remap.push(ws_root);
remap.push("=."); // remap to relative rustc work dir explicitly
} else {
remap.push(pkg_root);
remap.push("=");
remap.push(unit.pkg.name());
remap.push("-");
remap.push(unit.pkg.version().to_string());
}
remap
}

/// Remap all paths pointing to `build.build-dir`,
/// i.e., `[BUILD_DIR]/debug/deps/foo-[HASH].dwo` would be remapped to
/// `/cargo/build-dir/debug/deps/foo-[HASH].dwo`
/// (note the `/cargo/build-dir` prefix).
///
/// This covers scenarios like:
///
/// * Build script generated code. For example, a build script may call `file!`
/// macros, and the associated crate uses [`include!`] to include the expanded
/// [`file!`] macro in-place via the `OUT_DIR` environment.
/// * On Linux, `DW_AT_GNU_dwo_name` that contains paths to split debuginfo
/// files (dwp and dwo).
fn build_dir_remap(build_runner: &BuildRunner<'_, '_>) -> OsString {
let build_dir = build_runner.bcx.ws.build_dir();
let mut remap = OsString::new();
remap.push(build_dir.as_path_unlocked());
remap.push("=/cargo/build-dir");
remap
}

/// Generates the `--check-cfg` arguments for the `unit`.
fn check_cfg_args(unit: &Unit) -> Vec<OsString> {
// The routine below generates the --check-cfg arguments. Our goals here are to
Expand Down
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