`--all-features` can't build pmacs — luajit and lua54 select mlua's
mutually-exclusive Lua backends. Document the model so generic tooling
(CI, cargo hack, distro packaging) doesn't trip over it:
- README §Build: a feature-matrix table (luajit default / lua54 fallback /
orthogonal crdt), the supported build lines, and an explicit "don't use
--all-features".
- src/lib.rs crate docs: a "Lua flavor features" section stating the
exactly-one-flavor rule.
- Cargo.toml [features]: expanded comment on the mutual exclusivity.
CI already iterates the flavors explicitly (never --all-features), so no
CI change was needed.
The audit's suggested crate-local compile_error! for the wrong-flavor case
was investigated and rejected as unreachable: the flavor check lives in
the mlua-sys *build script*, which cargo compiles before the pmacs crate,
so a mis-set flavor (both or neither) fails there first and pmacs's own
compile_error! never evaluates — confirmed empirically for both cases. A
dependent crate can't preempt a dependency's build failure, so the docs
are the honest mitigation and they name mlua-sys as the actual error
surface.
Validated: fmt clean; clippy clean under both Lua flavors; both flavors
build.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014TXbAwk27agwhrNNrhLi2U
Levi Neuwirth
3b630bfee4