ci: disable cache-bin to fix flaky macOS builds#411
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Swatinem/rust-cache with cache-bin: true (the default) caches ~/.cargo/bin, which contains rustup proxy binaries. On macOS, rustup uses RUSTUP_PERMIT_COPY_RENAME=1, so these proxies are copies of the rustup binary. When the cache restores stale copies, they can resolve to rustup-init instead of the proper cargo proxy, causing: error: unexpected argument 'test' found Usage: rustup-init[EXE] [OPTIONS] Setting cache-bin: false prevents caching the bin directory, letting rustup manage its own proxy binaries correctly.
jlizen
approved these changes
May 15, 2026
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Problem
The macOS CI job flakes with:
This happens because
Swatinem/rust-cache@v2withcache-bin: true(the default) caches~/.cargo/bin. On macOS,dtolnay/rust-toolchainsetsRUSTUP_PERMIT_COPY_RENAME=1, so rustup proxy binaries (cargo,rustc, etc.) are copies of the rustup binary rather than hardlinks.When the cache restores these stale copies after a rustup version change on the runner image, the
cargobinary resolves torustup-initinstead of the proper proxy, breaking all cargo commands.Fix
Set
cache-bin: "false"soSwatinem/rust-cacheno longer caches~/.cargo/bin. Rustup manages its own proxy binaries; they should not be cached.This is a documented known issue in rust-cache.
Impact