clippy.toml

# D-09 (plan 48-09, TEST-01 / backlog 999.38).
#
# Process-global environment mutation is banned outside reasoned, test-only
# exceptions. `cargo test` runs its tests as THREADS in one process, so a
# mutation here is visible to every other concurrently running test and to
# every child process any of them spawns — which is exactly how a PATH change
# in one test made an unrelated test resolve (or fail to resolve) a binary.
# Rust 2024 already marks these `unsafe` for the same reason.
#
# The alternative is per-child scoping on the spawned command itself:
# `Command::env`, `Command::env_remove`, `Command::env_clear`. That reaches
# the process being configured and nothing else.
#
# Remaining non-PATH mutations are deferred deliberately (they still hold
# ENV_MUTEX) and each carries `#[expect(clippy::disallowed_methods, reason =
# "...")]` on its smallest enclosing test-only item. `expect` rather than
# `allow`: an expectation that stops being needed becomes a warning, so the
# exception list cannot silently outlive its reason.
disallowed-methods = [
  { path = "std::env::set_var", reason = "process-global and racy across concurrent tests and the children they spawn; scope it to the child with Command::env instead. Test-only exceptions need a reasoned expect(clippy::disallowed_methods)." },
  { path = "std::env::remove_var", reason = "process-global and racy across concurrent tests and the children they spawn; scope it to the child with Command::env_remove or Command::env_clear instead. Test-only exceptions need a reasoned expect(clippy::disallowed_methods)." },
]