Demonstrate validation code generation problem

src/Libraries/L1/BaseOptions.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace ValidationTest;
+
+public class BaseOptions
+{
+    [Timeout]
+    public int Prop1 { get; set; }
+}

src/Libraries/L1/BaseOptionsValidator.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Options.Validation;
+
+namespace ValidationTest;
+
+[OptionsValidator]
+internal sealed partial class BaseOptionsValidator : IValidateOptions<BaseOptions>
+{
+}

src/Libraries/L1/L1.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <UseOptionsValidationGenerator>true</UseOptionsValidationGenerator>
+    <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Microsoft.Extensions.Options.Validation\Microsoft.Extensions.Options.Validation.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Logging.Configuration" />
+    <PackageReference Include="OpenTelemetry" />
+  </ItemGroup>
+</Project>

src/Libraries/L1/TimeoutAttribute.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.ComponentModel.DataAnnotations;
+
+namespace ValidationTest;
+
+[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter, AllowMultiple = false)]
+internal sealed class TimeoutAttribute : ValidationAttribute
+{
+    protected override ValidationResult IsValid(object? value, ValidationContext? validationContext)
+    {
+        return ValidationResult.Success!;
+    }
+}

src/Libraries/L2/ExtOptions.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel.DataAnnotations;
+
+namespace ValidationTest;
+
+public class ExtOptions : BaseOptions
+{
+    [Range(0, 10)]
+    public int Prop2 { get; set; }
+}

src/Libraries/L2/ExtOptionsValidator.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.Extensions.Options;
+using Microsoft.Extensions.Options.Validation;
+
+namespace ValidationTest;
+
+[OptionsValidator]
+internal sealed partial class ExtOptionsValidator : IValidateOptions<ExtOptions>
+{
+}

src/Libraries/L2/L2.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <UseOptionsValidationGenerator>true</UseOptionsValidationGenerator>
+    <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\L1\L1.csproj" />
+  </ItemGroup>
+</Project>