fix(openapi3): Fix duplicate type name error for unreachable derived models with visibility properties

[Copilot]

When a model with @visibility(Lifecycle.Create, Lifecycle.Update) properties extends another model, and both are unreachable from HTTP operations, the OpenAPI3 emitter throws Duplicate type name: 'Account'.

Root Cause

Two code paths independently emit the derived model with different visibility contexts, bypassing the TypeEmitter deduplication cache:

1. processUnreferencedSchemas emits Account with Visibility.All context (correct for unreachable types).
2. modelDeclaration emits Account as a derived model inheriting the parent's reduced context (Visibility.Read — because Object has no transformed properties, so reduceContext downgrades it).

isTransformed(Account, All) = true (since item_id is present in All but absent in Read), so path 1 keeps All while path 2 produces Read. Two distinct cache keys → two #createDeclaration calls → same name → error.

Fix

In modelDeclaration, emit unreachable derived models with an explicit { visibility: Visibility.All } referenceContext, matching what processUnreferencedSchemas uses. This makes both paths produce the same context key — the TypeEmitter cache deduplicates on the second call.

model Object {}

model Account extends Object {
  @visibility(Lifecycle.Create, Lifecycle.Update)
  item_id: string;
}
// Previously: Duplicate type name: 'Account'
// Now: emits correctly as a single schema

Files changed:

• packages/openapi3/src/schema-emitter.ts — check isUnreachable per derived model in modelDeclaration loop; if unreachable, force Visibility.All referenceContext
• packages/openapi3/test/metadata.test.ts — add regression test for this case

• Fixes Can not derive model properties #9727

[azure-pipelines]

Azure Pipelines:
Successfully started running 1 pipeline(s).
1 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/openapi3@11427

commit: 840ac0a

[github-actions]

All changed packages have been documented.

• ✅ @typespec/openapi3

Show changes

@typespec/openapi3 - fix ✏️

Fix duplicate type name error when a model with a @visibility(Lifecycle.Create, Lifecycle.Update) property extends another model.

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension