fix issue #112: add new functions IsEmpty and IsTimeout

Author: kamilsk

semaphore.go

@@ -56,6 +56,16 @@ func New(capacity int) Semaphore {
 	return make(semaphore, capacity)
 }
 
+// IsEmpty checks if passed error is related to call Release on empty semaphore.
+func IsEmpty(err error) bool {
+	return err == errEmpty
+}
+
+// IsTimeout checks if passed error is related to call Acquire on full semaphore.
+func IsTimeout(err error) bool {
+	return err == errTimeout
+}
+
 var (
 	nothing ReleaseFunc = func() {}
 
@@ -68,7 +78,8 @@ type semaphore chan struct{}
 func (sem semaphore) Acquire(deadline <-chan struct{}) (ReleaseFunc, error) {
 	select {
 	case sem <- struct{}{}:
-		return releaser(sem), nil
+		//nolint: gas
+		return func() { _ = sem.Release() }, nil
 	case <-deadline:
 		return nothing, errTimeout
 	}
@@ -101,9 +112,3 @@ func (sem semaphore) Signal(deadline <-chan struct{}) <-chan ReleaseFunc {
 	}()
 	return ch
 }
-
-func releaser(releaser Releaser) ReleaseFunc {
-	return func() {
-		_ = releaser.Release() //nolint: gas
-	}
-}

semaphore_test.go

@@ -23,7 +23,7 @@ func TestSemaphore_Acquire_Timeout(t *testing.T) {
 	} {
 		sem := semaphore.New(0)
 		release, err := sem.Acquire(semaphore.WithTimeout(tc.timeout))
-		if err.Error() != expected {
+		if !semaphore.IsTimeout(err) {
 			t.Errorf("an unexpected error in test case %q. expected: %s; obtained: %v", tc.name, expected, err)
 		}
 		_ = release.Release()
@@ -66,7 +66,7 @@ func TestSemaphore_Occupied_Linearity(t *testing.T) {
 func TestSemaphore_Release_TryToGetDeadLock(t *testing.T) {
 	sem := semaphore.New(0)
 
-	if err, expected := sem.Release(), "semaphore is empty"; err.Error() != expected {
+	if err, expected := sem.Release(), "semaphore is empty"; !semaphore.IsEmpty(err) {
 		t.Errorf("an unexpected error. expected: %s; obtained: %v", expected, err)
 	}
 }