Added TryAdd to ComponentParameterCollectionBuilder to enable adding parameters to an builder with an unknown type

Author: egil

src/bunit.core/ComponentParameterCollectionBuilder.cs

@@ -14,6 +14,7 @@ namespace Bunit
 	/// <typeparam name="TComponent">The type of component under test to add the parameters</typeparam>
 	public sealed class ComponentParameterCollectionBuilder<TComponent> where TComponent : IComponent
 	{
+		private static readonly Type TComponentType = typeof(TComponent);
 		private const string ChildContent = nameof(ChildContent);
 
 		/// <summary>
@@ -303,6 +304,38 @@ public ComponentParameterCollectionBuilder<TComponent> AddUnmatched(string name,
 			return AddParameter(name, value);
 		}
 
+		/// <summary>
+		/// Try to add a <paramref name="value"/> for a parameter with the <paramref name="name"/>, if
+		/// <typeparamref name="TComponent"/> has a property with that name, AND that property has a <see cref="ParameterAttribute"/>
+		/// or a <see cref="CascadingParameterAttribute"/>.
+		/// </summary>
+		/// <remarks>
+		/// This is an untyped version of the <see cref="Add{TValue}(Expression{Func{TComponent, TValue}}, TValue)"/> method. Always
+		/// prefer the strongly typed <c>Add</c> methods whenever possible.
+		/// </remarks>
+		/// <typeparam name="TValue">Value type.</typeparam>
+		/// <param name="name">Name of the property for the parameter.</param>
+		/// <param name="value">Value to assign to the parameter</param>
+		/// <returns>True if parameter with the name exists and value was set, false otherwise.</returns>
+		public bool TryAdd<TValue>(string name, [AllowNull] TValue value)
+		{
+			if (TComponentType.GetProperty(name, BindingFlags.Public | BindingFlags.Instance) is PropertyInfo ccProp)
+			{
+				if (ccProp.GetCustomAttribute<ParameterAttribute>(inherit: false) is not null)
+				{
+					AddParameter(name, value);
+					return true;
+				}
+
+				if(ccProp.GetCustomAttribute<CascadingParameterAttribute>(inherit: false) is CascadingParameterAttribute cpa)
+				{
+					AddCascadingValueParameter(cpa.Name, value);
+					return true;
+				}
+			}
+			return false;
+		}
+
 		/// <summary>
 		/// Builds the <see cref="ComponentParameterCollection"/>.
 		/// </summary>
@@ -325,8 +358,8 @@ private static (string paramName, string? cascadingValueName, bool isCascading)
 		}
 
 		private static bool HasChildContentParameter()
-			=> typeof(TComponent).GetProperty(ChildContent, BindingFlags.Public | BindingFlags.Instance) is PropertyInfo ccProp
-				&& ccProp.GetCustomAttribute<ParameterAttribute>(inherit: false) != null;
+			=> TComponentType.GetProperty(ChildContent, BindingFlags.Public | BindingFlags.Instance) is PropertyInfo ccProp
+				&& ccProp.GetCustomAttribute<ParameterAttribute>(inherit: false) is not null;
 
 		private ComponentParameterCollectionBuilder<TComponent> AddParameter<TValue>(string name, [AllowNull] TValue value)
 		{

tests/bunit.core.tests/ComponentParameterCollectionBuilderTests.cs

@@ -494,6 +494,56 @@ public void Test101()
 			builder.Build().ShouldHaveSingleItem();
 		}
 
+		[Fact(DisplayName = "TryAdd returns false when parameter does not exist on component")]
+		public void Test200()
+		{
+			var sut = new ComponentParameterCollectionBuilder<NoParams>();
+
+			var result = sut.TryAdd("FOO", "VALUE");
+
+			result.ShouldBeFalse();
+			sut.Build().Count.ShouldBe(0);
+		}
+
+		[Fact(DisplayName = "TryAdd returns true when parameter exists on component")]
+		public void Test201()
+		{
+			var name = nameof(Params.ValueTypeParam);
+			var input = 42;
+
+			var result = Builder.TryAdd(name, input);
+
+			result.ShouldBeTrue();
+			Builder.Build().ShouldHaveSingleItem()
+				.ShouldBeParameter(name, input, isCascadingValue: false);
+		}
+
+		[Fact(DisplayName = "TryAdd returns true when unnamed cascading parameter exists on component")]
+		public void Test202()
+		{
+			var name = nameof(Params.CC);
+			var input = 42;
+
+			var result = Builder.TryAdd(name, input);
+
+			result.ShouldBeTrue();
+			Builder.Build().ShouldHaveSingleItem()
+				.ShouldBeParameter(null, input, isCascadingValue: true);
+		}
+
+		[Fact(DisplayName = "TryAdd returns true when named cascading parameter exists on component")]
+		public void Test203()
+		{
+			var name = nameof(Params.NamedCC);
+			var input = 42;
+
+			var result = Builder.TryAdd(name, input);
+
+			result.ShouldBeTrue();
+			Builder.Build().ShouldHaveSingleItem()
+				.ShouldBeParameter(name + "NAME", input, isCascadingValue: true);
+		}
+
 		private class Params : ComponentBase
 		{
 			[Parameter(CaptureUnmatchedValues = true)] public IReadOnlyDictionary<string, object>? Attributes { get; set; }