[Bug]: http-server-csharp: Generated model file is empty and produces a warning: Inline models use generated names in emitted code. Consider defining each model with an explicit name.

[abatishchev]

Describe the bug

All warnings:

typespec/node_modules/@azure-tools/typespec-azure-core/lib/traits.tsp:147:20 - warning @typespec/http-server-csharp/anonymous-model: Inline models use generated names in emitted code. Consider defining each model with an explicit name.  This model will be named 'Model0' in emitted code
> 147 |   clientRequestId: {};
      |                    ^^
typespec/node_modules/@azure-tools/typespec-azure-core/lib/traits.tsp:177:24 - warning @typespec/http-server-csharp/anonymous-model: Inline models use generated names in emitted code. Consider defining each model with an explicit name.  This model will be named 'Model1' in emitted code
> 177 |   conditionalRequests: {};
      |                        ^^
typespec/node_modules/@azure-tools/typespec-azure-core/lib/traits.tsp:206:23 - warning @typespec/http-server-csharp/anonymous-model: Inline models use generated names in emitted code. Consider defining each model with an explicit name.  This model will be named 'Model2' in emitted code
> 206 |   repeatableRequests: {};
      |                       ^^

Resulting C# class:

// Generated by @typespec/http-server-csharp
// <auto-generated />
#nullable enable

using System;
using System.Collections.Generic;
using System.Text.Json;
using TypeSpec.Helpers;
using TypeSpec.Helpers.JsonConverters;

namespace Microsoft.MyRpNamespace;

public partial class Model0 {}

Reproduction

1. Use an ARM RP typespec
2. Add the following to tspconfig.yaml

emit:
  - "@typespec/http-server-csharp"
options:
  "@typespec/http-server-csharp":
    emitter-output-dir: "{project-root}/generated/{emitter-name}"
    output-type: all
    emit-mocks: none
    overwrite: true

Checklist

• Follow our Code of Conduct
• Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion.
• The provided reproduction is a minimal reproducible example of the bug.

[github-actions]

🎯 Issue Triage

The http-server-csharp emitter generates an empty C# class (Model0 {}) for an inline anonymous model defined in @azure-tools/typespec-azure-core traits, accompanied by an anonymous-model warning.

Category: Bug
Area: emitter:service:csharp

🔁 Possible duplicate of #11448 — Both issues involve http-server-csharp emitting models with auto-generated numeric names (ModelN) from anonymous/inline types; this issue additionally highlights the empty class body when the inline model has no properties (e.g., clientRequestId: {}).

⚠️ No TypeSpec reproduction provided. The issue originates from @azure-tools/typespec-azure-core/lib/traits.tsp:147 which defines clientRequestId: {} as an inline empty model.

🔍 Analysis

• The warning @typespec/http-server-csharp/anonymous-model is triggered by clientRequestId: {} at line 147 of @azure-tools/typespec-azure-core/lib/traits.tsp — an inline anonymous model with no properties.
• The emitter assigns it the generated name Model0 and emits an empty partial class.
• This is a variant of [Bug]: http-server-csharp: Some generated model files have a generic, numbered name #11448: when the anonymous model has no properties, the resulting class body is completely empty, making the generated code essentially useless.
• The root cause is that the emitter does not skip or suppress emission of empty anonymous models derived from external library types.
• Affected component: packages/http-server-csharp (emitter logic for anonymous/inline model handling).

📝 Suggested next steps

• Investigate whether Model0 (from clientRequestId: {}) should be suppressed/skipped since it's an empty model from a library type
• Consider whether anonymous models from external library files (e.g., node_modules/) should be excluded from emission
• Link/close as duplicate of [Bug]: http-server-csharp: Some generated model files have a generic, numbered name #11448 if the fix there covers empty-body anonymous models as well

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