Prevent exception if there are no options types with the attribute.

OptionsBindingsGenerator.UnitTests/Tests.cs

@@ -17,6 +17,31 @@
         implementationAssembly = GetAssembly("OptionsBindingsGenerator");
     }
 
+    [Test]
+    public async Task NoBindings()
+    {
+        var source = await ReadCSharpFile<NoBindingsOptions>(true);
+
+        await new VerifyCS.Test
+        {
+            CompilerDiagnostics = CompilerDiagnostics.None,
+            TestState = {
+                ReferenceAssemblies = ReferenceAssemblies.Net.Net90,
+                AdditionalReferences =
+                {
+                    implementationAssembly,
+                    GetAssembly("TestLibrary")
+                },
+
+                Sources = { source },
+                GeneratedSources =
+                {
+
+                },
+            },
+        }.RunAsync();
+    }
+
     [Test]
     public async Task MixedBindings()
     {
@@ -66,9 +91,9 @@
     {
         var currentDirectory = GetCurrentDirectory();
 
         var targetDirectory = isTestLibrary ? GetTestLibraryDirectory(currentDirectory) : currentDirectory;
 
         var file = targetDirectory.GetFiles(searchPattern).First();
 
         using var fileReader = new StreamReader(file.OpenRead());
         return await fileReader.ReadToEndAsync();
@@ -76,10 +101,10 @@
 
     private static DirectoryInfo? GetCurrentDirectory()
     {
         return Directory.GetParent(Directory.GetParent(AppDomain.CurrentDomain.BaseDirectory).Parent.Parent.FullName);
     }
 
     private static DirectoryInfo GetTestLibraryDirectory(DirectoryInfo currentDirectory)
     {
         return currentDirectory.Parent.GetDirectories("TestLibrary").First();
     }

OptionsBindingsGenerator/Main.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Immutable;
+using System.Linq;
 using System.Text;
 using System.Threading;
 using Microsoft.CodeAnalysis;
@@ -36,9 +37,12 @@ private static INamedTypeSymbol GetSemanticTargetForGeneration(GeneratorAttribut
 
         private static void Execute(SourceProductionContext context, ImmutableArray<INamedTypeSymbol> typeSymbols)
         {
-            var (source, className) = OutputGenerator.GenerateOutput(typeSymbols);
+            if (typeSymbols.Any())
+            {
+                var (source, className) = OutputGenerator.GenerateOutput(typeSymbols);
 
-            context.AddSource($"{className}.generated.cs", SourceText.From(source, Encoding.UTF8, SourceHashAlgorithm.Sha256));
+                context.AddSource($"{className}.generated.cs", SourceText.From(source, Encoding.UTF8, SourceHashAlgorithm.Sha256));
+            }
         }
     }
 }

TestLibrary/NoBindingsOptions.cs

@@ -0,0 +1,11 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace TestLibrary;
+
+internal record NoBindingsOptions
+{
+    [Required]
+    public required string ServiceHost { get; init; }
+
+    public required string Port { get; init; }
+}