Add GetArgumentListAsync to resource extentions

src/Aspire.Hosting/ApplicationModel/ResourceExtensions.cs

@@ -316,6 +316,49 @@ public static int GetReplicaCount(this IResource resource)
         }
     }
 
+    /// <summary>
+    /// Get the arguments from the given resource.
+    /// </summary>
+    /// <remarks>
+    /// This method is useful when you want to make sure the arguments are added properly to resources, mostly in test situations.
+    /// This method has asynchronous behavior when arguments were provided from <see cref="IValueProvider"/> otherwise it will be synchronous.
+    /// </remarks>
+    /// <param name="resource">The resource to get the arguments from.</param>
+    /// <returns>The arguments retrieved from the resource.</returns>
+    public static async ValueTask<IReadOnlyList<string>> GetArgumentListAsync(this IResourceWithArgs resource)
+    {
+        var finalArgs = new List<string>();
+
+        if (resource.TryGetAnnotationsOfType<CommandLineArgsCallbackAnnotation>(out var exeArgsCallbacks))
+        {
+            var args = new List<object>();
+            var commandLineContext = new CommandLineArgsCallbackContext(args, default);
+
+            foreach (var exeArgsCallback in exeArgsCallbacks)
+            {
+                await exeArgsCallback.Callback(commandLineContext).ConfigureAwait(false);
+            }
+
+            foreach (var arg in args)
+            {
+                var value = arg switch
+                {
+                    string s => s,
+                    IValueProvider valueProvider => await valueProvider.GetValueAsync().ConfigureAwait(false),
+                    null => null,
+                    _ => throw new InvalidOperationException($"Unexpected value for {arg}")
+                };
+
+                if (value is not null)
+                {
+                    finalArgs.Add(value);
+                }
+            }
+        }
+
+        return finalArgs;
+    }
+
     /// <summary>
     /// Gets the lifetime type of the container for the specified resource.
     /// Defaults to <see cref="ContainerLifetime.Session"/> if no <see cref="ContainerLifetimeAnnotation"/> is found.

src/Aspire.Hosting/PublicAPI.Unshipped.txt

@@ -213,6 +213,7 @@ Aspire.Hosting.LaunchSettings.Profiles.get -> System.Collections.Generic.Diction
 Aspire.Hosting.LaunchSettings.Profiles.set -> void
 Aspire.Hosting.Utils.VolumeNameGenerator
 static Aspire.Hosting.ApplicationModel.CommandResults.Success() -> Aspire.Hosting.ApplicationModel.ExecuteCommandResult!
+static Aspire.Hosting.ApplicationModel.ResourceExtensions.GetArgumentListAsync(this Aspire.Hosting.ApplicationModel.IResourceWithArgs! resource) -> System.Threading.Tasks.ValueTask<System.Collections.Generic.IReadOnlyList<string!>!>
 static Aspire.Hosting.ApplicationModel.ResourceExtensions.GetEnvironmentVariableValuesAsync(this Aspire.Hosting.ApplicationModel.IResourceWithEnvironment! resource, Aspire.Hosting.DistributedApplicationOperation applicationOperation = Aspire.Hosting.DistributedApplicationOperation.Run) -> System.Threading.Tasks.ValueTask<System.Collections.Generic.Dictionary<string!, string!>!>
 Aspire.Hosting.ApplicationModel.ResourceNotificationService.WaitForResourceAsync(string! resourceName, string? targetState = null, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task!
 Aspire.Hosting.ApplicationModel.ResourceNotificationService.WaitForResourceAsync(string! resourceName, System.Collections.Generic.IEnumerable<string!>! targetStates, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) -> System.Threading.Tasks.Task<string!>!

tests/Aspire.Hosting.Tests/ResourceExtensionsTests.cs

@@ -259,6 +259,32 @@ public async Task GetEnvironmentVariableValuesAsyncReturnCorrectVariablesUsingMa
             });
     }
 
+    [Fact]
+    public async Task GetArgumentListAsyncReturnCorrectArguments()
+    {
+        var builder = DistributedApplication.CreateBuilder();
+        builder.Configuration["Parameters:DummyKey"] = "DummyValue";
+
+        var dummyParameter = builder.AddParameter("DummyKey").Resource;
+        var resource = new DummyResource("dummy");
+        var container = builder.AddResource(resource)
+         .WithArgs(["--arg1", "--arg2"])
+         .WithArgs(context =>
+         {
+             context.Args.Add("--arg3");
+         })
+         .WithArgs(dummyParameter);
+
+        var args = await container.Resource.GetArgumentListAsync().DefaultTimeout();
+
+        Assert.Collection(args,
+            arg => Assert.Equal("--arg1", arg),
+            arg => Assert.Equal("--arg2", arg),
+            arg => Assert.Equal("--arg3", arg),
+            arg => Assert.Equal("DummyValue", arg)
+            );
+    }
+
     private sealed class ParentResource(string name) : Resource(name)
     {
 
@@ -278,4 +304,9 @@ private sealed class AnotherDummyAnnotation : IResourceAnnotation
     {
 
     }
+
+    private sealed class DummyResource(string name) : Resource(name), IResourceWithArgs
+    {
+
+    }
 }