fix(http-server-csharp): honor models-only output

[sophia-ramsey]

This pull request updates the @typespec/http-server-csharp emitter to fully support the output-type: models option, ensuring that only models and their required support files are emitted when this option is set. The implementation introduces a new option to control operation canonicalization, updates the emitter logic to honor the models-only output, and adds comprehensive tests to verify the new behavior.

Enhancements to models-only output:

• The emitter now checks for the output-type: models option and, when enabled, emits only models and essential support files, skipping controllers, operations, mocks, and project files. [1] [2] [3]

Service type resolution improvements:

• Added a ServiceTypeResolutionOptions interface and updated the resolveServiceTypes function to accept a canonicalizeOperations flag, allowing it to skip HTTP operation canonicalization when only models are being emitted. [1] [2] [3]

Testing and validation:

• Introduced new tests to ensure that when output-type: models is set, only model files and required support files are generated, and no controllers, operations, mocks, or project files are emitted.
• Added a unit test to verify that operation canonicalization is skipped when disabled.

Documentation:

• Added a change note describing the fix and its effect.

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commit: a8a4a67

[github-actions]

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• ✅ @typespec/http-server-csharp

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@typespec/http-server-csharp - fix ✏️

Honor output-type: models by emitting only models and their required support files.

[azure-sdk-automation]

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[Copilot]

🟢 Approval recommended

The changes correctly gate non-model outputs for output-type: models, avoid unnecessary canonicalization, and include targeted tests plus a valid .chronus fix entry.

Pull request overview

This PR updates the @typespec/http-server-csharp emitter to correctly honor the output-type: models option by suppressing non-model artifacts (controllers, operations, mocks, project files, and docs) while still emitting models plus required shared support code.

Changes:

• Gate controller/interface generation, Program.cs, and documentation emission behind a modelsOnly check in the emitter entrypoint.
• Add a ServiceTypeResolutionOptions flag to skip HTTP operation canonicalization when operation artifacts won’t be emitted.
• Add/extend tests to verify models-only output behavior and that canonicalization is not invoked when disabled.

File summaries

File	Description
packages/http-server-csharp/test/emitter.test.ts	Adds an integration-style emitter test asserting that output-type: models only emits models + required support files and skips controllers/ops/mocks/project/docs.
packages/http-server-csharp/src/service-resolution.ts	Introduces ServiceTypeResolutionOptions and conditionally skips operation canonicalization when configured.
packages/http-server-csharp/src/service-resolution.test.ts	Adds a unit test to validate canonicalization is skipped (and HttpCanonicalizer.canonicalize is not called) when disabled.
packages/http-server-csharp/src/emitter.tsx	Implements modelsOnly gating for operation/controller/program/docs emission and passes canonicalization option accordingly.
.chronus/changes/fix-csharp-models-only-output-2026-9-8.md	Adds a fix changelog entry for the user-visible behavior correction.

Review details

• Files reviewed: 5/5 changed files
• Comments generated: 0
• Review effort level: Lite

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[Timothee Guerin (timotheeguerin)]

Models-only output still appears to include an ASP.NET-dependent action filter. The unconditional <JsonConverters /> call also emits HttpServiceExceptionFilter, including its Microsoft.AspNetCore.Mvc imports and IActionFilter/IOrderedFilter dependencies.

Even a simple model Pet { name: string; } with output-type: models therefore carries controller infrastructure into the generated output. Consuming those files in a normal Microsoft.NET.Sdk class library requires ASP.NET references, despite only requesting models.

Could we separate the HttpServiceException base class, which @error models need, from the action filter and its ASP.NET imports, and emit the filter only when generating server output?

[Copilot]

🟡 Changes recommended

Add explicit framework usings to HttpServiceException before approval.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

• Files reviewed: 9/11 changed files
• Comments generated: 1
• Review effort level: Lite

[Copilot]

🟢 Approval recommended

No unresolved review comments were supplied, and the changes include focused tests and snapshots.

Review details

• Files reviewed: 9/11 changed files
• Comments generated: 0 new
• Review effort level: Lite