ADD: FailOnSetupNotStarted, FailOnSetupUnsuccessful

CHANGELOG.md

@@ -18,8 +18,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - `AsyncServiceSetupResult.Unsuccessful` means that `SetupAsync` completed with a `false` result;
   - `AsyncServiceSetupResult.Canceled` means that `SetupAsync` was canceled;
   - `AsyncServiceSetupResult.Faulted` means that `SetupAsync` threw an exception.
+- Two new boolean properties in `AsyncHostedService` lets subclasses decide whether `StartAsync` should fail when the service is stopped before starting (`FailOnSetupNotStarted`) or `SetupAsync` completes with `false` (`FailOnSetupUnsuccessful`).  
+The default value is `true` for both properties.
 
-### Changes to existing features
+                                                                                     ### Changes to existing features
 
 - **BREAKING CHANGE:** In class `Louis.Threading.AsyncService`, methods `StartAsync` and `StopAsync` have been renamed to `StartAndWaitAsync` and `StopAndWaitAsync`, respectively. The old names lead some users (and code analysis tools, e.g. ReSharper) to believe they were asynchronous versions of `Start` and `Stop`.
 

src/Louis.Hosting/AsyncHostedService.cs

@@ -29,17 +29,33 @@ protected AsyncHostedService(ILogger logger)
         _logger = logger;
     }
 
+    /// <summary>
+    /// Gets a value indicating whether <see cref="IHostedService.StartAsync"/> will fail if
+    /// the result of <see cref="AsyncService.SetupAsync"/> is <see cref="AsyncServiceSetupResult.NotStarted"/>.
+    /// </summary>
+    protected virtual bool FailOnSetupNotStarted => true;
+
+    /// <summary>
+    /// Gets a value indicating whether <see cref="IHostedService.StartAsync"/> will fail if
+    /// the result of <see cref="AsyncService.SetupAsync"/> is <see cref="AsyncServiceSetupResult.Unsuccessful"/>.
+    /// </summary>
+    protected virtual bool FailOnSetupUnsuccessful => true;
+
     /// <inheritdoc/>
     async Task IHostedService.StartAsync(CancellationToken cancellationToken)
     {
         LogHostedServiceStarting();
         var setupResult = await StartAndWaitAsync(cancellationToken).ConfigureAwait(false);
-        if (setupResult == AsyncServiceSetupResult.Successful)
+        switch (setupResult)
         {
-            return;
+            case AsyncServiceSetupResult.Successful:
+            case AsyncServiceSetupResult.NotStarted when !FailOnSetupNotStarted:
+            case AsyncServiceSetupResult.Unsuccessful when !FailOnSetupUnsuccessful:
+                break;
+            default:
+                ThrowHelper.ThrowInvalidOperationException($"Service start failed ({setupResult}).");
+                break;
         }
-
-        ThrowHelper.ThrowInvalidOperationException($"Service start failed ({setupResult}).");
     }
 
     /// <inheritdoc/>

src/Louis.Hosting/PublicAPI.Unshipped.txt

@@ -1,3 +1,5 @@
 #nullable enable
 *REMOVED*override sealed Louis.Hosting.AsyncHostedService.LogSetupCompleted() -> void
 override sealed Louis.Hosting.AsyncHostedService.LogSetupCompleted(bool success) -> void
+virtual Louis.Hosting.AsyncHostedService.FailOnSetupNotStarted.get -> bool
+virtual Louis.Hosting.AsyncHostedService.FailOnSetupUnsuccessful.get -> bool