Invalidate the full constructor with the constructor cache

[JoshLove-msft]

Summary

• centralize constructor-cache invalidation in a private protected hook
• clear ModelProvider.FullConstructor whenever the constructor list is invalidated
• cover same-value identity updates that still rebuild customization and declaration metadata

Context

Follow-up to #11737. That fix keys FullConstructor only on name and namespace, but Update(name: provider.Name) still invalidates Constructors while preserving that identity. Derived providers that mutate FullConstructor during BuildConstructors then apply those mutations repeatedly. This is exercised downstream by Azure/azure-sdk-for-net#61958 while fixing Azure/azure-sdk-for-net#61851.

Validation

• Microsoft.TypeSpec.Generator ModelProviderTests (166 passed)
• targeted constructor cache tests (2 passed)

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/http-client-csharp@11745

commit: 5526d4c

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[Copilot]

Pull request overview

This PR refines constructor caching in the C# generator’s provider layer by centralizing constructor-cache invalidation and ensuring ModelProvider.FullConstructor is rebuilt whenever the constructor list is invalidated (including “same identity” updates). This prevents repeated application of constructor mutations when providers rebuild constructors without changing name/namespace.

Changes:

• Introduces a constructor-reset hook in TypeProvider and routes constructor invalidation through it.
• Clears ModelProvider’s cached FullConstructor whenever constructors are reset.
• Extends regression coverage to include same-value identity updates that still force constructor rebuilds.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/TypeProvider.cs	Centralizes constructor invalidation through a dedicated reset hook used by Reset() and identity-based updates.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/src/Providers/ModelProvider.cs	Hooks constructor invalidation to also clear the cached FullConstructor, simplifying FullConstructor caching logic.
packages/http-client-csharp/generator/Microsoft.TypeSpec.Generator/test/Providers/ModelProviders/ModelProviderTests.cs	Adds regression assertions for same-identity Update calls to ensure FullConstructor is rebuilt and mutations aren’t duplicated.

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[JoshLove-msft]

Validated this fix against the downstream management generator path from Azure/azure-sdk-for-net#61958:

• removed the management-local constructor cache workaround
• replaced the runtime Microsoft.TypeSpec.Generator.dll with this branch's build
• passed all 42 DynamicModelConstructorTests and FlattenPropertyVisitorTests
• regenerated the Mgmt-TypeSpec project through the actual emitter/generator pipeline
• regeneration produced no output diff, with exactly one _patch = patch; assignment per dynamic model constructor

Restoring the published 20260821.2 core generator reproduces the duplicate assignments, propagator calls, and pragmas.

--generated by Copilot

[JoshLove-msft]

Jorge Rangel (@jorgerangel-msft) this is the follow-up to #11737 for the same-value identity update path that the identity tuple does not catch. Full CI is green, and I validated it end-to-end against Azure/azure-sdk-for-net#61958 with the local workaround removed: 42 focused tests pass and regeneration is unchanged. When you have a chance, could you review this follow-up?

--generated by Copilot