Refine normalized bridge direct path and env guard

src/mir/join_ir/normalized/dev_env.rs

@@ -0,0 +1,38 @@
+#![cfg(feature = "normalized_dev")]
+
+use once_cell::sync::Lazy;
+use std::sync::Mutex;
+
+/// RAII guard for normalized_dev env toggling (NYASH_JOINIR_NORMALIZED_DEV_RUN).
+/// 汚染防止のため tests/runner の両方で再利用できるようにここに置く。
+pub struct NormalizedDevEnvGuard {
+    _lock: std::sync::MutexGuard<'static, ()>,
+    prev: Option<String>,
+}
+
+static NORMALIZED_ENV_LOCK: Lazy<Mutex<()>> = Lazy::new(|| Mutex::new(()));
+
+impl NormalizedDevEnvGuard {
+    pub fn new(enabled: bool) -> Self {
+        let lock = NORMALIZED_ENV_LOCK
+            .lock()
+            .expect("normalized env mutex poisoned");
+        let prev = std::env::var("NYASH_JOINIR_NORMALIZED_DEV_RUN").ok();
+        if enabled {
+            std::env::set_var("NYASH_JOINIR_NORMALIZED_DEV_RUN", "1");
+        } else {
+            std::env::remove_var("NYASH_JOINIR_NORMALIZED_DEV_RUN");
+        }
+        Self { _lock: lock, prev }
+    }
+}
+
+impl Drop for NormalizedDevEnvGuard {
+    fn drop(&mut self) {
+        if let Some(prev) = &self.prev {
+            std::env::set_var("NYASH_JOINIR_NORMALIZED_DEV_RUN", prev);
+        } else {
+            std::env::remove_var("NYASH_JOINIR_NORMALIZED_DEV_RUN");
+        }
+    }
+}