Docs: Mention required valueType for struct scalars in Strawberry Shake (#8575)

Author: N-Olbert

src/StrawberryShake/CodeGeneration/test/CodeGeneration.CSharp.Tests/ScalarGeneratorTests.cs

@@ -1,4 +1,5 @@
 using ChilliCream.Testing;
+using Xunit.Sdk;
 using static StrawberryShake.CodeGeneration.CSharp.GeneratorTestHelper;
 
 namespace StrawberryShake.CodeGeneration.CSharp;
@@ -95,6 +96,34 @@ public void Custom_Scalar_With_SerializationType_And_RuntimeType() =>
                     @serializationType(name: ""global::System.Int32"")",
             "extend schema @key(fields: \"id\")");
 
+    [Fact]
+    public void Custom_Scalar_With_ValueType_RuntimeType() =>
+        AssertResult(
+            "query GetId($modelId: ModelIdScalar!) { personId(id: $modelId) }",
+            "type Query { personId(id: ModelIdScalar!): ModelIdScalar }",
+            "scalar ModelIdScalar",
+            @"extend scalar ModelIdScalar
+                    @runtimeType(name: ""global::StrawberryShake.CodeGeneration.CSharp.ModelId"" valueType: true)");
+
+    [Fact]
+    public void Custom_Scalar_With_ValueType_RuntimeType_Used_As_Nullable_Input() =>
+        AssertResult(
+            "query GetId($modelId: ModelIdScalar) { personId(id: $modelId) }",
+            "type Query { personId(id: ModelIdScalar): ModelIdScalar }",
+            "scalar ModelIdScalar",
+            @"extend scalar ModelIdScalar
+                    @runtimeType(name: ""global::StrawberryShake.CodeGeneration.CSharp.ModelId"" valueType: true)");
+
+    [Fact]
+    public void Custom_Scalar_With_ValueType_RuntimeType_Fails_If_ValueType_Not_Specified() =>
+        Assert.Throws<FailException>(() =>
+            AssertResult(
+            "query GetId($modelId: ModelIdScalar!) { personId(id: $modelId) }",
+            "type Query { personId(id: ModelIdScalar!): ModelIdScalar }",
+            "scalar ModelIdScalar",
+            @"extend scalar ModelIdScalar
+                    @runtimeType(name: ""global::StrawberryShake.CodeGeneration.CSharp.ModelId"")"));
+
     [Fact]
     public void Any_Scalar() =>
         AssertResult(
@@ -187,3 +216,5 @@ public void Uri_Type() =>
 }
 
 public class Custom;
+
+public record struct ModelId(long Id);