Fix parse_rustc_z_ls for deps without -HASH suffix

[justdoGIT]

Summary

Fixes #2846

parse_rustc_z_ls misparses dependency lines from rustc -Z ls=root when a crate appears without a -${HASH} suffix. The malformed dependency name never matches during crate_link_paths scanning, so the dep's rmeta is not packaged for the distributed worker, and the worker fails with:

error[E0463]: can't find crate for `crc_fast` which `xai_file_utils` depends on

Root cause

Modern rustc emits extended metadata per dependency line:

=External Dependencies=
1 std-453218b5e9634890 hash c76be37... host_hash None kind Unconditional public
2 crc_fast hash 05bce60290e56777e3ae6d3ddcc01e6c host_hash None kind Unconditional public
3 crc-8c7d86e779319534 hash 49e85fac... host_hash None kind Unconditional public

Line 2 (crc_fast) has no -${HASH} suffix; line 3 (crc-8c7d...) does.

parse_rustc_z_ls does line.splitn(2, ' ') which splits on the first space, so libstring becomes the entire trailing metadata ("crc_fast hash 05bce6... host_hash None kind Unconditional public"). The subsequent rsplitn(2, '-') finds no - and libname becomes the whole string.

When RustInputsPackager scans -L paths, it parses each rmeta filename (e.g. libcrc_fast-c6657c97868f5464.rmeta) and extracts "crc_fast", but dep_crate_names contains the broken "crc_fast hash 05bce6..." — no match. The rmeta is silently skipped, not sent to the worker, and rustc on the worker fails with E0463.

The fix

Take only the first whitespace-delimited token of libstring before the existing rsplitn('-') logic runs, so crates with and without a -${HASH} suffix both resolve to the bare crate name:

let libstring = line_splits
    .next()
    .context("No lib string on line from rustc -Z ls")?;
// The libstring may contain additional metadata after the crate name
// (e.g., "crc_fast hash 05bce6... host_hash None kind Unconditional public"
// when the crate has no -HASH suffix). Take only the first
// whitespace-delimited token so rsplitn('-') below operates on just
// the crate name, not the entire trailing metadata.
let libstring = libstring
    .split_whitespace()
    .next()
    .context("No lib string on line from rustc -Z ls")?;

This preserves the existing behavior for deps with a -${HASH} suffix (rsplitn('-') still splits std-453218b5e9634890 → std).

Test

Added test_parse_rustc_z_ls_modern_no_hash_suffix which feeds the parser a modern -Z ls output containing both a no-suffix dep (crc_fast) and a suffix dep (crc-8c7d...), and asserts each resolves to the bare crate name. This test fails on the unfixed parser (the crc_fast entry becomes the entire metadata string) and passes with the fix.

Checklist

• Added a regression test covering the no-hash-suffix case
• Existing test_parse_rustc_z_ls_pre_1_55 and test_parse_rustc_z_ls_post_1_55 still pass (old format deps also take the first token correctly)

[Copilot]

🟢 Approval recommended

The fix and regression coverage address the reported dependency-packaging failure with no unresolved review issues.

Pull request overview

This pull request fixes parsing of Rust dependencies without -HASH suffixes, ensuring required metadata is packaged for distributed builds.

Changes:

• Parses only the first crate-name token.
• Adds regression coverage for hashed and unhashed dependencies.

File summaries

File	Description
src/compiler/rust.rs	Fixes dependency parsing and adds focused tests.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.69%. Comparing base (4ffa89b) to head (f7d27e5).

❗ There is a different number of reports uploaded between BASE (4ffa89b) and HEAD (f7d27e5). Click for more details.

HEAD has 8 uploads less than BASE

Flag	BASE (4ffa89b)	HEAD (f7d27e5)
	14	6

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2847      +/-   ##
==========================================
- Coverage   76.14%   67.69%   -8.46%     
==========================================
  Files          72       72              
  Lines       39807    38627    -1180     
==========================================
- Hits        30313    26147    -4166     
- Misses       9494    12480    +2986     

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[justdoGIT]

Superseded by #2850 which consolidates all fixes onto a single branch.