Search manifest ancestors for the lockfile when fetching cargo metadata - #23296
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Search manifest ancestors for the lockfile when fetching cargo metadata#23296onlycs wants to merge 1 commit into
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…data The rustc-dev dist component ships the compiler sources with `rustc-src/rust/compiler/rustc/Cargo.toml` as the entry manifest, but without a workspace root manifest next to the lockfile, which lives at `rustc-src/rust/Cargo.lock`. FetchMetadata only looked for a lockfile right next to the manifest, so for `rust-analyzer.rustc.source = "discover"` setups the metadata fetch ran with `--locked` and no usable lockfile. On read-only toolchain installations (e.g. rustup toolchains on nix) cargo then fails to create one, and rust-analyzer silently degrades to `--no-deps` metadata, dropping rustc_middle and friends from the crate graph entirely - rustc_private projects lose all type information for rustc crates. Walk up from the manifest to find the lockfile and reuse the existing lockfile-copy mechanism, which keeps cargo from touching the original. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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This was referenced Sep 4, 2026
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Problem
With a nix toolchain, every macro-generated
TyCtxtquery getter (tcx.mir_keys(()), e.g.) resolves to{unknown}. Three independent bugs cause this, one of which was fixed in 7015591, one with #23297, and one in this PRthe
rustc-srclockfile is never foundThe
rustc-devcomponent ships compiler sources as[rustc-src]/rust/compiler/rustc/Cargo.toml, with no workspace root manifest. The lockfile lives two levels up at[rustc-src]/rust/Cargo.lock.FetchMetadata::newonly looks for a lockfile directly next to the manifest, so the rustc metadata fetch runs--lockedwith no lockfile available. In a read-only store, cargo cannot create one and errors:FetchMetadata::execthen silently falls back to the--no-depspre-fetch, whose metadata contains only therustc-mainstub package.rustc_middle,rustc_hir, etc. never enter the crate graph.Instead, we walk up the manifest's ancestor directories to find the lockfile, then reuse the existing lockfile-copy mechanism.
AI disclosure
These changes were authored with AI assistance (Claude Code); the commits carry
Co-Authored-Bytrailers. I have reviewed the changes, use them in a current project using a patched build, and can answer questions about them myself.See also: #23251
Version Info
cargo:
cargo 1.99.0-nightly (eb98b54bc 2026-08-11)Toolchain:
nightly-2026-08-14, componentsrustc-dev,llvm-tools-preview,rust-src.Configuration (Zed,
.zed/settings.json):{ "lsp": { "rust-analyzer": { "initialization_options": { "rustc": { "source": "discover" } } } } }