WhitWaldo · Aug 26, 2026 · Aug 26, 2026
@@ -406,6 +406,8 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Store.Next.Example07.Tests"
 EndProject
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Store.Next.Example07.AppHost", "examples\Actor.Next\07-PerTypeOptions\Store.Next.Example07.AppHost\Store.Next.Example07.AppHost.csproj", "{B620B816-53AB-4DB1-B038-CCA35234AB0C}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Dapr.Workflow.Versioning.Generators.Test", "test\Dapr.Workflow.Versioning.Generators.Test\Dapr.Workflow.Versioning.Generators.Test.csproj", "{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -2408,6 +2410,18 @@ Global
 		{B620B816-53AB-4DB1-B038-CCA35234AB0C}.Release|x64.Build.0 = Release|Any CPU
 		{B620B816-53AB-4DB1-B038-CCA35234AB0C}.Release|x86.ActiveCfg = Release|Any CPU
 		{B620B816-53AB-4DB1-B038-CCA35234AB0C}.Release|x86.Build.0 = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|x64.ActiveCfg = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|x64.Build.0 = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Debug|x86.Build.0 = Debug|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|Any CPU.Build.0 = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|x64.ActiveCfg = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|x64.Build.0 = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|x86.ActiveCfg = Release|Any CPU
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -2606,6 +2620,7 @@ Global
 		{9D3FA169-444F-4B8A-921E-17962829E457} = {451E5A30-5AC1-E437-EC03-1F862D847C4D}
 		{9C989F53-0991-4E47-A4D3-6E1EF76537D6} = {451E5A30-5AC1-E437-EC03-1F862D847C4D}
 		{B620B816-53AB-4DB1-B038-CCA35234AB0C} = {451E5A30-5AC1-E437-EC03-1F862D847C4D}
+		{FCDA0406-5FD9-4ACB-A3B1-C2685B034809} = {DD020B34-460F-455F-8D17-CF4A949F100B}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {65220BF2-EAE1-4CB2-AA58-EBE80768CB40}

@@ -126,6 +126,13 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
                         Diagnostic: (string?)$"Rejected '{symbolName}': does not inherit from Workflow<,> (base type: {baseTypeInfo})");
                 }
 
+                // Abstract or open-generic types cannot be instantiated; skip them.
+                if (symbol.IsAbstract || symbol.TypeParameters.Length > 0)
+                {
+                    return (Workflow: (DiscoveredWorkflow?)null,
+                        Diagnostic: (string?)$"Rejected '{symbolName}': abstract or open-generic workflow types are not registered.");
+                }
+
                 // Look for [WorkflowVersion] by symbol identity
                 AttributeData? attrData = null;
                 if (ks.WorkflowVersionAttribute is not null)
@@ -410,6 +417,10 @@ private static IEnumerable<DiscoveredWorkflow> DiscoverReferencedWorkflows(
             if (!InheritsFromWorkflow(type, knownSymbols.WorkflowBase))
                 continue;
 
+            // Skip abstract types and open generics — they can't be instantiated.
+            if (type.IsAbstract || type.TypeParameters.Length > 0)
+                continue;
+
             AttributeData? attrData = null;
             if (knownSymbols.WorkflowVersionAttribute is not null)
             {

@@ -0,0 +1,67 @@
+// ------------------------------------------------------------------------
+// Copyright 2026 The Dapr Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//     http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ------------------------------------------------------------------------
+
+// Regression coverage for https://github.com/dapr/dotnet-sdk/issues/1898
+//
+// An abstract *closed* (non-generic) workflow isolates the IsAbstract filter independent of
+// the open-generic filter. The source generator must skip it, so neither its type name nor
+// its declared canonical name may appear in the generated versioning registry.
+//
+// Gated to C# 16 / .NET 14 (which ships with the Dapr SDK 1.19 release) — this scenario is
+// not exercised on prior target frameworks. The Dapr SDK 1.19 release will add .NET 14
+// support; until that merge, this test is dormant (the type and test are compiled out).
+
+#if NET14_0_OR_GREATER
+using Dapr.Testcontainers.Xunit.Attributes;
+using Dapr.Workflow;
+using Dapr.Workflow.Versioning;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Dapr.IntegrationTest.Workflow.Versioning;
+
+internal static class AbstractClosedWorkflowConstants
+{
+    public const string CanonicalName = "AbstractClosedWorkflow";
+}
+
+[WorkflowVersion(CanonicalName = AbstractClosedWorkflowConstants.CanonicalName, Version = "1")]
+internal abstract class AbstractClosedWorkflow : Workflow<string, string>
+{
+}
+
+public sealed class AbstractClosedWorkflowRegressionTests
+{
+    /// <summary>
+    /// The abstract closed (non-generic) workflow must be excluded from the generated
+    /// versioning registry: its declared canonical name must not be a registry key, and its
+    /// type name must not appear in any registered workflow list.
+    /// </summary>
+    [MinimumDaprRuntimeFact("1.19")]
+    public void AbstractClosedWorkflow_IsExcludedFromVersioningRegistry()
+    {
+        var services = new ServiceCollection();
+        services.AddLogging();
+        services.AddDaprWorkflowVersioning();
+        services.AddDaprWorkflowBuilder(configureRuntime: _ => { });
+
+        using var provider = services.BuildServiceProvider();
+        var registry = GeneratedWorkflowVersionRegistry.GetWorkflowVersionRegistry(provider);
+
+        Assert.False(registry.ContainsKey(AbstractClosedWorkflowConstants.CanonicalName),
+            "The abstract closed workflow's canonical name must not appear as a registry key.");
+        Assert.DoesNotContain(
+            registry.SelectMany(kv => kv.Value),
+            v => v.Contains(nameof(AbstractClosedWorkflow), StringComparison.Ordinal));
+    }
+}
+#endif
@@ -0,0 +1,38 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+        <IsPackable>false</IsPackable>
+        <IsTestProject>true</IsTestProject>
+        <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
+    </PropertyGroup>
+
+    <ItemGroup>
+        <PackageReference Include="coverlet.collector">
+            <PrivateAssets>all</PrivateAssets>
+            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+        </PackageReference>
+        <PackageReference Include="Microsoft.NET.Test.Sdk" />
+        <PackageReference Include="Microsoft.CodeAnalysis.CSharp" />
+        <PackageReference Include="xunit.v3" />
+        <PackageReference Include="xunit.runner.visualstudio">
+            <PrivateAssets>all</PrivateAssets>
+            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+        </PackageReference>
+    </ItemGroup>
+
+    <ItemGroup>
+        <Using Include="Xunit" />
+    </ItemGroup>
+
+    <ItemGroup>
+        <!-- The generator under test (normal reference so the test can instantiate it). -->
+        <ProjectReference Include="..\..\src\Dapr.Workflow.Versioning.Generators\Dapr.Workflow.Versioning.Generators.csproj" />
+        <!-- Abstractions (so the generator resolves Workflow`2/WorkflowActivity`2 and the test source compiles). -->
+        <ProjectReference Include="..\..\src\Dapr.Workflow.Abstractions\Dapr.Workflow.Abstractions.csproj" />
+        <ProjectReference Include="..\..\src\Dapr.Workflow.Versioning.Abstractions\Dapr.Workflow.Versioning.Abstractions.csproj" />
+    </ItemGroup>
+
+</Project>
@@ -0,0 +1,100 @@
+// ------------------------------------------------------------------------
+// Copyright 2026 The Dapr Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//     http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// ------------------------------------------------------------------------
+
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+
+namespace Dapr.Workflow.Versioning.Generators.Test;
+
+/// <summary>
+/// In-process harness that runs <see cref="WorkflowSourceGenerator"/> over a snippet of
+/// user source and returns the generated registry source plus generator diagnostics.
+/// </summary>
+internal static class GeneratorTestHarness
+{
+    public const string RegistryGeneratedFileName = "Dapr_Workflow_Versioning.g.cs";
+
+    private static MetadataReference AbstractionsReference()
+    {
+        var path = Path.Combine(AppContext.BaseDirectory, "Dapr.Workflow.Abstractions.dll");
+        return MetadataReference.CreateFromFile(path);
+    }
+
+    private static MetadataReference VersioningAbstractionsReference()
+    {
+        var path = Path.Combine(AppContext.BaseDirectory, "Dapr.Workflow.Versioning.Abstractions.dll");
+        return MetadataReference.CreateFromFile(path);
+    }
+
+    /// <summary>
+    /// Compiles <paramref name="userSource"/> and runs the source generator, returning the
+    /// generated registry source (or an empty string when the generator emits nothing) and
+    /// any diagnostics the generator reports.
+    /// </summary>
+    public static Task<(string GeneratedSource, Diagnostic[] Diagnostics)> RunAsync(string userSource)
+    {
+        // Build a complete reference set from the assemblies already loaded into the test host
+        // (System.Runtime, System.Text.Json, Microsoft.Extensions.*, etc.) plus the abstractions
+        // assemblies under test. This avoids the fragility of hand-picking individual framework refs.
+        var references = AppDomain.CurrentDomain.GetAssemblies()
+            .Where(a => !a.IsDynamic && !string.IsNullOrEmpty(a.Location))
+            .Select(MetadataReference? (a) => MetadataReference.CreateFromFile(a.Location))
+            .Where(r => r is not null)
+            .Cast<MetadataReference>()
+            .ToList();
+        references.Add(AbstractionsReference());
+        references.Add(VersioningAbstractionsReference());
+
+        var compilation = CSharpCompilation.Create(
+            assemblyName: "TestAssembly",
+            syntaxTrees: new[] { CSharpSyntaxTree.ParseText(userSource) },
+            references: references,
+            options: new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary, nullableContextOptions: NullableContextOptions.Enable));
+
+        var generator = new WorkflowSourceGenerator();
+        GeneratorDriver driver = CSharpGeneratorDriver.Create(generator);
+        driver = driver.RunGenerators(compilation);
+        var runResult = driver.GetRunResult();
+
+        var generated = string.Empty;
+        foreach (var tree in runResult.GeneratedTrees.Where(tree => tree.FilePath.EndsWith(RegistryGeneratedFileName, StringComparison.Ordinal)))
+        {
+            generated = tree.ToString();
+        }
+
+        return Task.FromResult((generated, runResult.Diagnostics.ToArray()));
+    }
+
+    /// <summary>Asserts that no error-severity diagnostics were reported by the generator.</summary>
+    public static void AssertNoErrorDiagnostics(Diagnostic[] diagnostics)
+    {
+        var errors = diagnostics.Where(d => d.Severity == DiagnosticSeverity.Error).ToList();
+        Assert.True(errors.Count == 0,
+            $"Expected no error diagnostics, but got: {string.Join("; ", errors.Select(d => d.ToString()))}");
+    }
+
+    /// <summary>
+    /// Re-parses the generated source and asserts it is syntactically valid C#. This catches
+    /// generator defects such as an orphan <c>else</c> branch (the root cause of issue #1898).
+    /// </summary>
+    public static void AssertNoSyntaxErrors(string source)
+    {
+        if (string.IsNullOrEmpty(source))
+            return;
+
+        var tree = CSharpSyntaxTree.ParseText(source);
+        var errors = tree.GetDiagnostics().Where(d => d.Severity == DiagnosticSeverity.Error).ToList();
+        Assert.True(errors.Count == 0,
+            $"Expected no syntax errors in generated source, but got: {string.Join("; ", errors.Select(d => d.ToString()))}");
+    }
+}