Preserve opaque JSON reference properties in C# code-model deserialization

[Copilot]

The reference pre-scan treats user-owned $id properties as code-model metadata, causing repeated JSON Schema IDs to collide with each other or generated references.

• Opaque payloads: Exclude unknown and union example value subtrees from indexing. Continue scanning their types and decorator-held graph definitions.
• Reserved wire names: Treat only string-valued dictionary $id entries as metadata, preserving object-valued $id example properties alongside $ref and $values.

For example, these payload properties remain user data—not reference instructions:

{
  "kind": "unknown",
  "type": { "kind": "unknown" },
  "value": {
    "$id": "https://example.com/person.schema.json",
    "$ref": "#/definitions/person",
    "$values": []
  }
}

• Fixes C# code-model reference pre-scan misinterprets $id in opaque JSON payloads #12022

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[pkg-pr-new]

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npm i https://pkg.pr.new/@typespec/http-client-csharp@12026

commit: aeeccfc

[Copilot]

Copilot review overview

🟡 Changes recommended

Unresolved compatibility, graph-identity, and resource-bound problems can produce rejected or incorrect code models.

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Review effort: Balanced
Findings: 2 · 2

Open (4)

• Preserve legacy format for the Autorest writeCodeModel path · New
• Enforce node and byte limits for cyclic graph envelopes · New
• Reject re-entry into active arrays · New
• Export withRawJson from the emitter package root · New

What changed in this PR

Introduces a versioned C# code-model format that preserves opaque JSON properties while retaining object-reference support and legacy input compatibility.

Changes:

• Adds v2 envelope, key escaping, and raw JSON handling.
• Updates deserialization and cyclic-reference processing.
• Adds documentation, fixtures, and regression tests.

File	Description
packages/​http-client-csharp/​readme.md	Documents the v2 format and compatibility behavior.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​test/​TypeSpecInputExampleConverterTests.cs	Tests opaque example preservation and reference handling.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​test/​TypeSpecInputConverterTests.cs	Tests v2 decoding, references, cycles, and limits.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​test/​TestData/​TypeSpecInputConverterTests/​LoadsVersionedEmitterFixture/​tspCodeModel.json	Provides an emitter-compatible v2 fixture.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​Serialization/​Utf8JsonReaderExtensions.cs	Decodes escaped dictionary and decorator data.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​Serialization/​TypeSpecSerialization.cs	Detects and loads versioned envelopes.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​Serialization/​TypeSpecReferenceHandler.cs	Separates metadata indexing from opaque legacy values.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​Serialization/​TypeSpecJsonConverter.cs	Expands and encodes referenced raw JSON graphs.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​Serialization/​InputDecoratorInfoConverter.cs	Tracks graph-encoded decorator arguments.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.Input/​src/​InputTypes/​InputDecoratorInfo.cs	Exposes encoded-argument metadata.
packages/​http-client-csharp/​emitter/​test/​Unit/​code-model-writer.test.ts	Tests v2 serialization and opaque data preservation.
packages/​http-client-csharp/​emitter/​src/​lib/​raw-json.ts	Adds opaque-property markers.
packages/​http-client-csharp/​emitter/​src/​lib/​example-converter.ts	Marks union and unknown example values as raw JSON.
packages/​http-client-csharp/​emitter/​src/​code-model-writer.ts	Emits v2 envelopes and escapes data keys.

---

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[Jorge Rangel (jorgerangel-msft)]

Copilot it looks like we have a stackoverflow that needs to be addressed. In addition, we should always ensure we run the full test suite before pushing changes:

Versioning.RenamedFrom.V1 -> D:\a\_work\1\s\packages\http-client-csharp\generator\artifacts\bin\Versioning.RenamedFrom.V1\Debug\net8.0\Versioning.RenamedFrom.V1.dll
The active test run was aborted. Reason: Test host process crashed : Stack overflow.
   at System.Text.Json.Serialization.JsonConverter`1[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].ReadCore(System.Text.Json.Utf8JsonReader ByRef, System.__Canon ByRef, System.Text.Json.JsonSerializerOptions, System.Text.Json.ReadStack ByRef)
   at System.Reflection.MethodBaseInvoker.InterpretedInvoke_Method(System.Object, IntPtr*)
   at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(System.Object, System.Reflection.BindingFlags)
   at System.Reflection.RuntimeMethodInfo.Invoke(System.Object, System.Reflection.BindingFlags, System.Reflection.Binder, System.Object[], System.Globalization.CultureInfo)
   at System.Reflection.MethodBase.Invoke(System.Object, System.Object[])
   at NUnit.Framework.Internal.Reflect.InvokeMethod(System.Reflection.MethodInfo, System.Object, System.Object[])
   at NUnit.Framework.Internal.MethodWrapper.Invoke(System.Object, System.Object[])
   at NUnit.Framework.Internal.Commands.TestMethodCommand.InvokeTestMethod(NUnit.Framework.Internal.TestExecutionContext)
   at NUnit.Framework.Internal.Commands.TestMethodCommand.RunTestMethod(NUnit.Framework.Internal.TestExecutionContext)
   at NUnit.Framework.Internal.Commands.TestMethodCommand.Execute(NUnit.Framework.Internal.TestExecutionContext)
   at NUnit.Framework.Internal.Execution.SimpleWorkItem+<>c__DisplayClass4_0.<PerformWork>b__0()
   at NUnit.Framework.Internal.ContextUtils+<>c__DisplayClass1_0`1[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].<DoIsolated>b__0(System.Object)
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object)
   at NUnit.Framework.Internal.ContextUtils.DoIsolated(System.Threading.ContextCallback, System.Object)
   at NUnit.Framework.Internal.ContextUtils.DoIsolated[[System.__Canon, System.Private.CoreLib, Version=10.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]](System.Func`1<System.__Canon>)
   at NUnit.Framework.Internal.Execution.SimpleWorkItem.PerformWork()
   at NUnit.Framework.Internal.Execution.WorkItem.RunOnCurrentThread()
   at NUnit.Framework.Internal.Execution.WorkItem.Execute()
   at NUnit.Framework.Internal.Execution.ParallelWorkItemDispatcher.Dispatch(NUnit.Framework.Internal.Execution.WorkItem, NUnit.Framework.Internal.Execution.ParallelExecutionStrategy)
   at NUnit.Framework.Internal.Execution.ParallelWorkItemDispatcher.Dispatch(NUnit.Framework.Internal.Execution.WorkItem)
   at NUnit.Framework.Internal.Execution.CompositeWorkItem.RunChildren()
   at NUnit.Framework.Internal.Execution.CompositeWorkItem.PerformWork()
   at NUnit.Framework.Internal.Execution.WorkItem.RunOnCurrentThread()
   at NUnit.Framework.Internal.Execution.WorkItem.Execute()
   at NUnit.Framework.Internal.Execution.TestWorker.TestWorkerThreadProc()
   at System.Threading.Thread.StartCallback()

[Copilot]

Copilot it looks like we have a stackoverflow that needs to be addressed. In addition, we should always ensure we run the full test suite before pushing changes:

Addressed in a066c67c with regression coverage in aeeccfcc.

The stack overflow was caused by very deep nested reference expansion recursing through JsonSerializer.Deserialize before the existing JSON MaxDepth guard was reached on Windows. Reference resolution is now capped independently below the platform stack limit, so excessive/cyclic reference chains fail with the existing JsonException message instead of crashing the test host. I added ReferenceResolutionStopsBeforePlatformStackOverflow to cover a chain that is still within the JSON document-depth limit but now fails cleanly.

Validation:

• dotnet test ./generator/Microsoft.TypeSpec.Generator.Input/test/Microsoft.TypeSpec.Generator.Input.Tests.csproj — passed, 273 tests.
• dotnet build ./generator/Microsoft.TypeSpec.Generator.Input/src/Microsoft.TypeSpec.Generator.Input.csproj — passed.
• dotnet test ./generator/TestProjects/Spector.Tests/TestProjects.Spector.Tests.csproj --filter "FullyQualifiedName~Versioning.RenamedFrom" — 3 tests discovered/skipped locally because node_modules is not present in this sandbox; no crash while building/loading Versioning.RenamedFrom.V1.
• Attempted full dotnet test ./generator; it progressed through building/loading the generated projects including Versioning.RenamedFrom.V1, but then hung locally in the generator test run and had to be stopped.
• Attempted canonical npm run test; blocked locally because emitter dependencies are not installed (vitest: not found).
• Changed-file dotnet format --verify-no-changes — passed. Broader format checks hit pre-existing unrelated formatting issues.
• Secret scan — passed.
• Final parallel validation — no review comments; CodeQL reported 0 alerts (C# analysis skipped due database size limits).

[Copilot]

Copilot review overview

🟡 Changes recommended

Non-string $id validation remains property-order dependent and can leak InvalidOperationException.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Validate $id token kind regardless of property order · New