ci: restore Homebrew stub removal on macOS (fixes broken main)#55
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PR #54 pinned to macos-14 and dropped the PATH workaround on the (incorrect) assumption that macos-14 didn't ship the broken Homebrew `cargo` wrapper. It does — same failure as macos-15, the very next main-push run after PR #54 broke. Re-runs reproduce deterministically. Restore the stub-removal approach from the closed PR #53, this time on top of the macos-14 pin so we get both: the marginally healthier runner image and an active defense that doesn't rely on PATH ordering. This is the version that should have shipped originally.
The earlier stub-removal step ran successfully but cargo build still failed with the same rustup-init error — there's a third location of the broken cargo wrapper we never found. Stop hunting for it. Invoke cargo via \$HOME/.cargo/bin/cargo directly. dtolnay/rust-toolchain installs the rustup-managed proxies there on every OS, so the same absolute path works for both Ubuntu and macOS — no matrix-conditional logic needed. When GitHub fixes the runner image upstream, this is a trivial one-line revert.
Root cause finally found via debug output: the Swatinem cache contains a poisoned ~/.cargo/bin/rustup symlink that points at /opt/homebrew/bin/rustup-init (Homebrew's broken wrapper). dtolnay installs a working ~/.cargo/bin/rustup as a real 11MB Mach-O binary; Swatinem then restores the symlink over it, and every subsequent `cargo build` resolves through the broken Homebrew binary and fails with "unexpected argument 'build'". Fix in one diff: - `cache-bin: "false"` — stop caching ~/.cargo/bin entirely. We don't need it cached; dtolnay installs fresh every run in seconds. - `prefix-key: "v1-rust"` — bump the cache-key namespace so the existing poisoned cache entries are abandoned and a clean cache is built from scratch. Both options applied uniformly to the test and lint jobs.
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mattfogel
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May 13, 2026
The original PR #54 pin to macos-14 was based on (incorrect) research claiming macos-14 was a clean escape hatch for the broken Homebrew rustup wrapper on macos-15. The actual root cause turned out to be a poisoned Swatinem cache, fixed in PR #55 with `cache-bin: false` and a prefix-key bump. With the real fix in place, macos-latest should work too. Trying it to keep the workflow aligned with GHA defaults. If this flakes, revert to macos-14 — that's the known-good fallback.
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Summary
Main is currently red. PR #54's premise — that pinning to `macos-14` would dodge the broken Homebrew `cargo` wrapper — was wrong. The same wrapper ships on macos-14; the post-merge main-push run failed deterministically (and so did the rebased Dependabot PR #51). Two re-runs reproduce.
This PR restores the stub-removal approach from the (incorrectly closed) PR #53, on top of the macos-14 pin. The cleanup step deletes `/opt/homebrew/bin/cargo` (and the rest of the Rust toolchain wrappers) before Swatinem runs, so the only Rust binaries on the runner after dtolnay finishes are the ones under `~/.cargo/bin`. No PATH races, no flakes.
`runner.os == 'macOS'` guard keeps it from running on the Ubuntu matrix entry.
Test plan
Refs: actions/runner-images#13985, Homebrew/homebrew-core#178311. Apologies for the churn.