Problem

startup_file_returns_psqlrc_env_when_set in src/repl/mod.rs intermittently fails in CI:

test repl::tests::startup_file_returns_psqlrc_env_when_set ... FAILED

Root cause

The test calls std::env::set_var("PSQLRC", ...) then std::env::remove_var("PSQLRC"). Rust test threads run in parallel by default. If another test reads PSQLRC between the set and remove, it sees an unexpected value. If two such tests run concurrently, one clobbers the other's state.

Same pattern affects RPG_TEST_API_KEY_12345 and RPG_EMPTY_KEY_TEST tests at lines ~7417-7435.

Fix

Add a process-wide mutex for env var mutation in tests:

// In mod tests:
static ENV_MUTEX: std::sync::LazyLock<std::sync::Mutex<()>> =
    std::sync::LazyLock::new(|| std::sync::Mutex::new(()));

Then wrap all env-mutating tests:

fn startup_file_returns_psqlrc_env_when_set() {
    let _guard = ENV_MUTEX.lock().unwrap();
    std::env::set_var("PSQLRC", "/tmp/test_rpg_rc");
    // ...
}

Affected tests

• startup_file_returns_psqlrc_env_when_set (line ~5750)
• startup_file_returns_none_when_no_rc_exists_and_no_env (line ~5758)
• api_key_env_reads_set_variable (line ~7417)
• api_key_env_returns_none_for_unset_variable (line ~7425)
• api_key_env_returns_none_for_empty_variable (line ~7432)