From 9ae7c65b06741434b3457c95fc45a6bcfac0673f Mon Sep 17 00:00:00 2001
From: Felix Winterhalter <felix@ranovus.com>
Date: Wed, 10 Dec 2025 15:44:10 +0100
Subject: [PATCH] fix: Non-Nullable String empty query parameter

Fixes: https://github.com/JasperFx/wolverine/issues/1924
---
 ...Bug_1924_NonNullableEmptyQueryParameter.cs | 60 +++++++++++++++++++
 .../Wolverine.Http/CodeGen/IReadHttpFrame.cs  |  2 +-
 2 files changed, 61 insertions(+), 1 deletion(-)
 create mode 100644 src/Http/Wolverine.Http.Tests/Bugs/Bug_1924_NonNullableEmptyQueryParameter.cs

diff --git a/src/Http/Wolverine.Http.Tests/Bugs/Bug_1924_NonNullableEmptyQueryParameter.cs b/src/Http/Wolverine.Http.Tests/Bugs/Bug_1924_NonNullableEmptyQueryParameter.cs
new file mode 100644
index 000000000..10afb0747
--- /dev/null
+++ b/src/Http/Wolverine.Http.Tests/Bugs/Bug_1924_NonNullableEmptyQueryParameter.cs
@@ -0,0 +1,60 @@
+using Alba;
+using IntegrationTests;
+using Marten;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.DependencyInjection;
+using Wolverine.Marten;
+
+namespace Wolverine.Http.Tests.Bugs;
+
+public class Bug_1924_NonNullableEmptyQueryParameter
+{
+    [Fact]
+    public async Task non_nullable_empty_string_query_parameters_dont_throw()
+    {
+        var builder = WebApplication.CreateBuilder([]);
+        
+        builder.Services.AddMarten(opts =>
+        {
+            // Establish the connection string to your Marten database
+            opts.Connection(Servers.PostgresConnectionString);
+            opts.DisableNpgsqlLogging = true;
+        }).IntegrateWithWolverine();
+        
+        builder.Host.UseWolverine(opts =>
+        {
+            opts.Discovery.DisableConventionalDiscovery().IncludeType<Bug1924Controller>();
+            opts.ApplicationAssembly = GetType().Assembly;
+        });
+
+        builder.Services.AddWolverineHttp();
+
+        // This is using Alba, which uses WebApplicationFactory under the covers
+        await using var host = await AlbaHost.For(builder, app => { app.MapWolverineEndpoints(); });
+
+        await host.Scenario(x =>
+        {
+            x.Get.Url("/bugs/1924/nullable?first=Test");
+            x.StatusCodeShouldBe(200);
+            x.ContentShouldBe("Test");
+        });
+        
+        await host.Scenario(x =>
+        {
+            x.Get.Url("/bugs/1924/nullable");
+            x.StatusCodeShouldBe(200);
+            x.ContentShouldBe("");
+        });
+    }
+}
+
+public class Bug1924Controller
+{
+    [WolverineGet("/bugs/1924/nullable", Name = "Bug1924_nullable")]
+    public string Get([FromQuery] string first)
+    {
+        if (first == null) throw new ArgumentNullException(nameof(first));
+        return first.ToString();
+    }
+}
diff --git a/src/Http/Wolverine.Http/CodeGen/IReadHttpFrame.cs b/src/Http/Wolverine.Http/CodeGen/IReadHttpFrame.cs
index 8fb8da59c..7c74bbeef 100644
--- a/src/Http/Wolverine.Http/CodeGen/IReadHttpFrame.cs
+++ b/src/Http/Wolverine.Http/CodeGen/IReadHttpFrame.cs
@@ -109,7 +109,7 @@ private void writeStringValue(ISourceWriter writer, GeneratedMethod method)
     {
         var assignTo = Mode == AssignMode.WriteToVariable ? $"var {Variable.Usage}" : _property;
         
-        writer.Write($"{assignTo} = {rawValueSource()};");
+        writer.Write($"{assignTo} = {rawValueSource()}?.ToString() {(_isNullable ? "" : "?? \"\"")};");
         
         if (_source == BindingSource.RouteValue)
         {