[http-client-csharp] Prevent List/Get request-builder collisions

[Copilot]

List-to-Get normalization collapsed singleton GET and pageable LIST operations onto the same REST request-builder signature, causing CS0111 despite their distinct request paths.

• Collision handling: Check stable input names and projected C# signatures before applying List-to-Get normalization. Retain the original List name when REST or public declarations would collide, including generated Async variants.
• Compatibility: Preserve non-colliding overloads and existing explicit, published-API, acronym, and URL naming. Compare generic arguments recursively so IEnumerable<int> and IEnumerable<int?> remain distinct signatures.
• Regression coverage: Cover operation order, explicit-name peers, List/GetAll and async-name collisions, valid overloads, unique declarations, and URI/lookup/initial-page/next-page binding.

GetByResourceGroup  → CreateGetByResourceGroupRequest  → …/singletonTrackedResources/default
ListByResourceGroup → CreateListByResourceGroupRequest → …/singletonTrackedResources

• Fixes [http-client-csharp] List/Get normalization creates duplicate REST request builders #12175

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commit: 7542403

[Copilot]

🟡 Changes recommended

False collision checks can unnecessarily rename existing APIs for exact-name peers and async-only streaming operations.

2 open findings

• Streaming operations reserve nonexistent synchronous API names · New
• Identifier conversion incorrectly reports public API collisions · New

What changed in this PR

Prevents C# List-to-Get normalization from creating duplicate request builders for distinct operations, addressing #12175.

Changes:

• Checks projected names and parameter signatures before normalization.
• Compares generic parameter types recursively.
• Adds regression coverage for collisions, valid overloads, and request binding.

File	Description
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator/​src/​Shared/​MethodSignatureHelper.cs	Recursively compares generic arguments.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.ClientModel/​test/​Providers/​ClientProviders/​ClientProviderTests.cs	Tests naming collisions, overloads, and request binding.
packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.ClientModel/​src/​Providers/​ClientProvider.cs	Adds collision-aware List normalization.

🧠 Review effort: Balanced

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[Copilot]

🟡 Changes recommended

Public-name collision checks run before URL projection and can unnecessarily rename valid existing APIs.

1 open finding

• Apply URL name projection before detecting operation name collisions · New

2 resolved since last review

• Identifier conversion incorrectly reports public API collisions
• Streaming operations reserve nonexistent synchronous API names

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Wrapper-dependent request-builder names and unnecessary URL-related API renames remain unresolved.

2 open findings

• Prevent request-builder loss across colliding wrapper operations · New
• Preserve GetUrl APIs when URL projection names collide · New

1 resolved since last review

• Apply URL name projection before detecting operation name collisions

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Wrapper-dependent REST naming can invalidate earlier calls, and pre-emission signature comparisons can rename valid APIs unnecessarily.

1 open finding

• Make REST collision resolution independent of provider ordering · New

2 resolved since last review

• Prevent request-builder loss across colliding wrapper operations
• Preserve GetUrl APIs when URL projection names collide

Previously missed (1)

In code that hasn't changed since last review

Compare final parameter order before detecting API collisions

packages/​http-client-csharp/​generator/​Microsoft.TypeSpec.Generator.ClientModel/​src/​Providers/​ClientProvider.cs:350

These parameter lists precede the sync/async reordering in ScmMethodProviderCollection.cs:1398–1450: for protocol-only ListWidgets and convenience-enabled GetWidgetsAsync, each with an optional string path parameter and a required int query parameter, the overlapping protocol declarations actually take (int, string, RequestOptions) and (string, int, RequestOptions). Comparing the identical pre-emission lists incorrectly renames the valid GetWidgets/GetWidgetsAsync API to ListWidgets/ListWidgetsAsync; compare each emitted variant's final parameter types and order, and add a regression for this pair.

🧠 Review effort: Balanced

[Copilot]

🟡 Changes recommended

Collision detection still misses next-page and reordered protocol signatures that can produce duplicate C# declarations.

2 open issues

• Detect collisions using filtered next-link signatures · New
• Compare final emitted signatures after parameter reordering · New

1 resolved since last review

• Make REST collision resolution independent of provider ordering

_{Review effort: Balanced}