Wait for GetOrAddAsync factory to return before reading from Absolute…

…ExpirationRelativeToNow (#160)

* fix: await addItemFactory before calling SetAbsoluteExpirationFromRelative

allows AbsoluteExpiration to be set properly when factories are long-running and a relative expiration is specified

fixes #148

* test: verify that AbsoluteExpiration is set properly from a relative expiration when a factory is long-running

* test: improve unit test names

LazyCache.UnitTests/CachingServiceMemoryCacheProviderTests.cs

@@ -790,6 +790,48 @@ public async Task GetOrAddAsyncWithAbsoluteOffsetExpiryInTheDelegateUsingTimeSpa
             Assert.That(expiredResult, Is.Null);
         }
 
+        [Test]
+        public async Task GetOrAddAsyncWithAbsoluteOffsetExpiryInTheDelegateAfterLongRunningTaskDoesExpireItems()
+        {
+            var millisecondsCacheDuration = 100;
+            var validResult = await sut.GetOrAddAsync(
+                TestKey,
+                async entry =>
+                {
+                    await Task.Delay(50);
+                    entry.SetAbsoluteExpiration(DateTimeOffset.Now.AddMilliseconds(millisecondsCacheDuration));
+                    return new ComplexTestObject();
+                }
+            );
+            // pass expiry time with a delay
+            Thread.Sleep(TimeSpan.FromMilliseconds(millisecondsCacheDuration + 50));
+            var expiredResult = sut.Get<ComplexTestObject>(TestKey);
+
+            Assert.That(validResult, Is.Not.Null);
+            Assert.That(expiredResult, Is.Null);
+        }
+
+        [Test]
+        public async Task GetOrAddAsyncWithAbsoluteOffsetExpiryInTheDelegateUsingTimeSpanAfterLongRunningTaskDoesExpireItems()
+        {
+            var millisecondsCacheDuration = 100;
+            var validResult = await sut.GetOrAddAsync(
+                TestKey,
+                async entry =>
+                {
+                    await Task.Delay(50);
+                    entry.SetAbsoluteExpiration(TimeSpan.FromMilliseconds(millisecondsCacheDuration));
+                    return new ComplexTestObject();
+                }
+            );
+            // pass expiry time with a delay
+            Thread.Sleep(TimeSpan.FromMilliseconds(millisecondsCacheDuration + 50));
+            var expiredResult = sut.Get<ComplexTestObject>(TestKey);
+
+            Assert.That(validResult, Is.Not.Null);
+            Assert.That(expiredResult, Is.Null);
+        }
+
         [Test]
         public void GetOrAddWithCancellationExpiryBasedOnTimerAndCallbackInTheDelegateDoesExpireItemsAndFireTheCallback()
         {

LazyCache/CachingService.cs

@@ -4,7 +4,6 @@
 using System.Threading.Tasks;
 using LazyCache.Providers;
 using Microsoft.Extensions.Caching.Memory;
-using Microsoft.Extensions.Primitives;
 
 namespace LazyCache
 {
@@ -201,9 +200,9 @@ public virtual async Task<T> GetOrAddAsync<T>(string key, Func<ICacheEntry, Task
             while (Interlocked.CompareExchange(ref keyLocks[hash], 1, 0) == 1) { Thread.Yield(); }
 
             object CacheFactory(ICacheEntry entry) =>
-                new AsyncLazy<T>(() =>
+                new AsyncLazy<T>(async () =>
                 {
-                    var result = addItemFactory(entry);
+                    var result = await addItemFactory(entry).ConfigureAwait(false);
                     SetAbsoluteExpirationFromRelative(entry);
                     EnsureEvictionCallbackDoesNotReturnTheAsyncOrLazy<T>(entry.PostEvictionCallbacks);
                     return result;
@@ -242,7 +241,6 @@ object CacheFactory(ICacheEntry entry) =>
                     result = GetValueFromAsyncLazy<T>(cacheItem, out _ /* we just evicted so type change cannot happen this time */);
                 }
 
-
                 if (result.IsCanceled || result.IsFaulted)
                     CacheProvider.Remove(key);