Exception thrown by ModelReaderContextWriter

[sbomer]

Using the ModelReaderWriter generation mode for Azure.Search.Documents hits a generator bug. This is blocking fixing some AOT warnings in azure-mcp. @JoshLove-msft @m-nash

System.ArgumentException: An item with the same key has already been added. Key: global::Azure.Search.Documents.Indexes.Models.KeywordTokenizer

   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value)
   at System.Linq.Enumerable.ToDictionary[TSource,TKey,TElement](IEnumerable1 source, Func2 keySelector, Func2 elementSelector, IEqualityComparer1 comparer)
   at AutoRest.CSharp.Common.Generation.Writers.ModelReaderWriterContextWriter.CollectBuildableTypes(IEnumerable`1 models) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\Generation\Writers\ModelReaderWriterContextWriter.cs:line 91
   at AutoRest.CSharp.Common.Generation.Writers.ModelReaderWriterContextWriter.Write(CodeWriter writer, IEnumerable`1 models) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\Generation\Writers\ModelReaderWriterContextWriter.cs:line 28
   at AutoRest.CSharp.AutoRest.Plugins.DataPlaneTarget.Execute(GeneratedCodeWorkspace project, InputNamespace inputNamespace, SourceInputModel sourceInputModel) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\DataPlane\AutoRest\DataPlaneTarget.cs:line 95
   at AutoRest.CSharp.AutoRest.Plugins.CSharpGen.ExecuteAsync(CodeModel codeModel) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Plugins\CSharpGen.cs:line 39
   at AutoRest.CSharp.AutoRest.Plugins.CSharpGen.Execute(IPluginCommunication autoRest) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Plugins\CSharpGen.cs:line 136
   at AutoRest.CSharp.AutoRest.Plugins.PluginProcessor.Start(IPluginCommunication autoRest) in D:\a\_work\1\s\autorest.csharp\src\AutoRest.CSharp\Common\AutoRest\Plugins\PluginProcessor.cs:line 39
fatal   | Process() cancelled due to failure 
error   |   Error: Plugin csharpgen reported failure

Repro:

1. clone https://github.com/sbomer/azure-sdk-for-net/tree/aiSearchMRW

   This branch is just main with

   use-model-reader-writer: true

   turned on in Azure.Search.Documents/src/autorest.md (and SDK roll-forward to make it easier to use a recent dotnet version)

2. dotnet build /t:GenerateCode sdk/search/Azure.Search.Documents/src/

   This fails. Running the inner npx command shows the stacktrace above.

[sbomer]

The exception is happening because these two schemas (KeywordTokenizer/KeywordTokenizerV2) are being mapped to the same C# name (KeywordTokenizer). What's the expected behavior for this?

https://github.com/Azure/azure-rest-api-specs/blob/1755004c92eefdc7a66b4cd90df27d0af4cb0456/specification/search/data-plane/Azure.Search/preview/2025-05-01-preview/searchservice.json#L4098-L4141