fix: prevent duplicate variant examples in oneOf dropdown for nested oneOf schemas

- Ensure top-level oneOf only expands variants at root without combinatorial duplication for nested properties
- Simplify mergePropertyExamples to update property values directly
- Fix property merging across allOf schemas in schemaToSampleObj
- Add visual test page and unit tests for oneOf example deduplication

fixes #1143

Author: mrin9

docs/generated-docs/rapidoc/rapidoc-min.js

@@ -0,0 +1,64 @@
+openapi: 3.1.0
+info:
+  title: oneOf Nested Example Validation
+  version: 1.0.0
+  description: Validates that top-level oneOf request body schemas with discriminator mappings list each variant exactly once in the EXAMPLE dropdown, even when sub-properties contain nested oneOf schemas.
+paths:
+  /things:
+    post:
+      summary: Create a Thing
+      description: Polymorphic Request body containing top-level oneOf variants (PlainVariant and NestedOneOfVariant), where NestedOneOfVariant contains a nested oneOf in EntryRef.
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/Request'
+      responses:
+        '200':
+          description: Successful response
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/Request'
+components:
+  schemas:
+    Request:
+      oneOf:
+        - $ref: '#/components/schemas/PlainVariant'
+        - $ref: '#/components/schemas/NestedOneOfVariant'
+      discriminator:
+        propertyName: kind
+        mapping:
+          plain: '#/components/schemas/PlainVariant'
+          nested: '#/components/schemas/NestedOneOfVariant'
+    PlainVariant:
+      title: PlainVariant
+      type: object
+      properties:
+        kind:
+          type: string
+          enum:
+            - plain
+        value:
+          type: string
+    NestedOneOfVariant:
+      title: NestedOneOfVariant
+      type: object
+      properties:
+        kind:
+          type: string
+          enum:
+            - nested
+        entry:
+          $ref: '#/components/schemas/EntryRef'
+    EntryRef:
+      oneOf:
+        - type: string
+        - $ref: '#/components/schemas/EntryObject'
+    EntryObject:
+      title: EntryObject
+      type: object
+      properties:
+        id:
+          type: string

docs/public/specs-test/oneof-duplicate-examples.yaml

@@ -158,6 +158,12 @@ advanced:
       title: Composite Schemas with Custom Tab Titles
       validates:
         - Rendering designated sub-schema titles on polymorphic tab selectors
+  - oneof-duplicate-examples:
+      title: Polymorphic oneOf with Nested oneOf Example Deduplication
+      validates:
+        - Request body EXAMPLE dropdown displays each top-level variant exactly once
+        - Nested oneOf in sub-properties do not create duplicate parent variant dropdown entries
+        - Clean polymorphic schema example generation with discriminator mapping
   - request-header-as-object:
       title: Serialized JSON Object in HTTP Request Headers
       validates:

docs/src/page-data/tests.yaml

@@ -0,0 +1,22 @@
+---
+import ExampleLayout from '../../layouts/ExampleLayout.astro';
+import { getSpecUrl } from '../../utils/getSpecUrl';
+
+const specUrl = getSpecUrl(Astro.url);
+---
+
+<ExampleLayout>
+  <rapi-doc 
+    id="thedoc"
+    spec-url="/specs-test/oneof-duplicate-examples.yaml" 
+    default-schema-tab="example"
+    render-style="read"
+    show-header="false"
+    allow-authentication="false" 
+    allow-server-selection="false"
+  > 
+    <div slot="nav-logo" style="display:flex; flex-direction:row; align-items:center; justify-content: center;">
+      <button class='btn' onclick="toggleSchemaStyle()">Toggle Schema Style</button>
+    </div>
+  </rapi-doc>
+</ExampleLayout>