hive-agent: test the in-agent socket's request dispatch

hive-agent/src/paths.rs

@@ -138,31 +138,50 @@ pub fn claude_dir() -> PathBuf {
 /// are serialised on a lock.
 #[cfg(test)]
 pub fn with_harness_dir<T>(f: impl FnOnce() -> T) -> T {
-    use std::ffi::OsString;
+    let _guard = harness_dir_guard();
+    f()
+}
+
+/// [`with_harness_dir`] for a test body that cannot be a closure: the harness
+/// dir stays set, and the lock stays held, until the guard drops.
+#[cfg(test)]
+pub fn harness_dir_guard() -> HarnessDirGuard {
     use std::sync::Mutex;
 
     static LOCK: Mutex<()> = Mutex::new(());
 
-    struct Restore(Option<OsString>);
-    impl Drop for Restore {
-        fn drop(&mut self) {
-            // SAFETY: still holding `LOCK`, the only writer of this variable.
-            unsafe {
-                match self.0.take() {
-                    Some(v) => std::env::set_var("HYPERHIVE_HARNESS_DIR", v),
-                    None => std::env::remove_var("HYPERHIVE_HARNESS_DIR"),
-                }
-            }
-        }
-    }
-
-    let _lock = LOCK
+    let lock = LOCK
         .lock()
         .unwrap_or_else(std::sync::PoisonError::into_inner);
     let dir = tempfile::tempdir().unwrap();
-    // Declared after `_lock` so the variable is restored before the lock drops.
-    let _restore = Restore(std::env::var_os("HYPERHIVE_HARNESS_DIR"));
+    let previous = std::env::var_os("HYPERHIVE_HARNESS_DIR");
     // SAFETY: serialised by `LOCK`.
     unsafe { std::env::set_var("HYPERHIVE_HARNESS_DIR", dir.path()) };
-    f()
+    HarnessDirGuard {
+        previous,
+        _dir: dir,
+        _lock: lock,
+    }
+}
+
+/// Holds `HYPERHIVE_HARNESS_DIR` at a fresh temp dir; see [`harness_dir_guard`].
+#[cfg(test)]
+pub struct HarnessDirGuard {
+    previous: Option<std::ffi::OsString>,
+    _dir: tempfile::TempDir,
+    // Declared last so the variable is restored (in `drop`) before the lock goes.
+    _lock: std::sync::MutexGuard<'static, ()>,
+}
+
+#[cfg(test)]
+impl Drop for HarnessDirGuard {
+    fn drop(&mut self) {
+        // SAFETY: still holding the lock, the only writer of this variable.
+        unsafe {
+            match self.previous.take() {
+                Some(v) => std::env::set_var("HYPERHIVE_HARNESS_DIR", v),
+                None => std::env::remove_var("HYPERHIVE_HARNESS_DIR"),
+            }
+        }
+    }
 }