feat: update library lifecycle return value

omrf/src/library_lifecycle.rs

@@ -82,15 +82,16 @@ impl<S> LibraryLifecycle<S> {
 
     /// Increment the reference count.
     ///
-    /// On the `0 -> 1` transition the supplied `init` closure runs and its produced `S` is stored.
-    /// If `init` fails, neither the count nor the state is changed and an error is returned.
+    /// On the `0 -> 1` transition the supplied `init` closure runs and its produced `S` is stored;
+    /// the call returns `Ok(true)`. If `init` fails, neither the count nor the state is changed and
+    /// an error is returned.
     ///
-    /// On any other call (count already `> 0`) the supplied `init` is **dropped without being run**
-    /// and the count is simply incremented.
+    /// On any other call (count already `> 0`) the supplied `init` is **dropped without being run**,
+    /// the count is simply incremented, and the call returns `Ok(false)`.
     ///
     /// The init closure runs under the write lock and must not re-enter this lifecycle. Its error
     /// type `E` is type-erased.
-    pub fn startup<E>(&self, init: impl FnOnce() -> Result<S, E>) -> Result<(), Error>
+    pub fn startup<E>(&self, init: impl FnOnce() -> Result<S, E>) -> Result<bool, Error>
     where
         E: std::error::Error + Send + Sync + 'static,
     {
@@ -99,22 +100,24 @@ impl<S> LibraryLifecycle<S> {
             let s = init().map_err(|e| Error::Init(Box::new(e)))?;
             inner.state = Some(s);
             inner.count = 1;
+            Ok(true)
         } else {
             inner.count += 1;
+            Ok(false)
         }
-        Ok(())
     }
 
     /// Decrement the reference count.
     ///
     /// On the `-> 0` transition the stored `S` is taken out and handed to the supplied `destroy`
-    /// closure, which must never fail (destructor semantics). On any other call (count stays `> 0`)
-    /// the supplied `destroy` is **dropped without being run** and the count is simply decremented.
+    /// closure, which must never fail (destructor semantics), and the call returns `Ok(true)`. On
+    /// any other call (count stays `> 0`) the supplied `destroy` is **dropped without being run**,
+    /// the count is simply decremented, and the call returns `Ok(false)`.
     ///
     /// Returns an error if the count was already zero.
     ///
     /// The destroy closure runs under the write lock and must not re-enter this lifecycle.
-    pub fn shutdown(&self, destroy: impl FnOnce(S)) -> Result<(), Error> {
+    pub fn shutdown(&self, destroy: impl FnOnce(S)) -> Result<bool, Error> {
         let mut inner = self.inner.write().expect("unexpected poison lock");
         if inner.count == 0 {
             return Err(Error::Underflow);
@@ -124,8 +127,10 @@ impl<S> LibraryLifecycle<S> {
             // Invariant: state is Some whenever count > 0.
             let s = inner.state.take().expect("state present while count > 0");
             destroy(s);
+            Ok(true)
+        } else {
+            Ok(false)
         }
-        Ok(())
     }
 
     /// Access the stored state by shared reference under a read lock.

omrf/tests/library_lifecycle.rs

@@ -16,24 +16,28 @@ struct State {
 }
 
 /// Coverage: a single paired startup/shutdown runs init once and destroy once, destroy receives the
-/// state produced by init, and the count returns to zero.
+/// state produced by init, both report that they ran the closure, and the count returns to zero.
 #[test]
 fn paired_startup_shutdown() {
     let inits = AtomicUsize::new(0);
     let destroys = AtomicUsize::new(0);
     let lc: LibraryLifecycle<State> = LibraryLifecycle::new();
 
-    lc.startup(|| -> Result<State, TestErr> {
+    let ran_init = lc
+        .startup(|| -> Result<State, TestErr> {
             inits.fetch_add(1, Ordering::SeqCst);
             Ok(State { value: 42 })
         })
         .unwrap();
+    assert!(ran_init);
 
-    lc.shutdown(|s| {
+    let ran_destroy = lc
+        .shutdown(|s| {
             destroys.fetch_add(1, Ordering::SeqCst);
             assert_eq!(s.value, 42);
         })
         .unwrap();
+    assert!(ran_destroy);
 
     assert_eq!(inits.load(Ordering::SeqCst), 1);
     assert_eq!(destroys.load(Ordering::SeqCst), 1);
@@ -42,29 +46,35 @@ fn paired_startup_shutdown() {
 
 /// Coverage: multiple startups followed by matching shutdowns run init and destroy only on the
 /// boundary transitions (once each); the init/destroy closures passed on non-transition calls are
-/// dropped without being run.
+/// dropped without being run, and the bool return reflects exactly which calls ran a closure.
 #[test]
 fn multiple_startups_shutdowns_run_only_on_boundaries() {
     let inits = AtomicUsize::new(0);
     let destroys = AtomicUsize::new(0);
     let lc: LibraryLifecycle<State> = LibraryLifecycle::new();
 
-    for _ in 0..3 {
+    let startup_ran: Vec<bool> = (0..3)
+        .map(|_| {
             lc.startup(|| -> Result<State, TestErr> {
                 inits.fetch_add(1, Ordering::SeqCst);
                 Ok(State { value: 7 })
             })
-        .unwrap();
-    }
+            .unwrap()
+        })
+        .collect();
+    assert_eq!(startup_ran, vec![true, false, false]);
     assert_eq!(lc.count(), 3);
     assert_eq!(inits.load(Ordering::SeqCst), 1);
 
-    for _ in 0..3 {
+    let shutdown_ran: Vec<bool> = (0..3)
+        .map(|_| {
             lc.shutdown(|_s| {
                 destroys.fetch_add(1, Ordering::SeqCst);
             })
-        .unwrap();
-    }
+            .unwrap()
+        })
+        .collect();
+    assert_eq!(shutdown_ran, vec![false, false, true]);
 
     assert_eq!(inits.load(Ordering::SeqCst), 1);
     assert_eq!(destroys.load(Ordering::SeqCst), 1);
@@ -79,15 +89,19 @@ fn reinitialization_runs_init_and_destroy_again() {
     let lc: LibraryLifecycle<State> = LibraryLifecycle::new();
 
     for _ in 0..2 {
-        lc.startup(|| -> Result<State, TestErr> {
+        let ran_init = lc
+            .startup(|| -> Result<State, TestErr> {
                 inits.fetch_add(1, Ordering::SeqCst);
                 Ok(State { value: 1 })
             })
             .unwrap();
-        lc.shutdown(|_s| {
+        assert!(ran_init);
+        let ran_destroy = lc
+            .shutdown(|_s| {
                 destroys.fetch_add(1, Ordering::SeqCst);
             })
             .unwrap();
+        assert!(ran_destroy);
     }
 
     assert_eq!(inits.load(Ordering::SeqCst), 2);