fix(schema example): xml gen should follow json gen behavior (#6555)

* ref: #6470 
* fixes: #6540
* fixes: #4943 

* add example override option to json
* add example override option to xml
* added basic oneOf and anyOf support
* fix anyof|oneof
* only lift xml to items


Co-authored-by: Tim Lai <timothy.lai@gmail.com>

test/e2e-cypress/static/documents/bugs/4943.yaml

@@ -0,0 +1,43 @@
+openapi: 3.0.0
+info:
+  description: Test API
+  version: v1
+  title: Test API
+tags:
+  - name: Test
+    description: Test API
+servers:
+  - url: /v1
+paths:
+  /test:
+    post:
+      tags:
+        - Test
+      summary: Test endpoint
+      description: Test
+      operationId: postTest
+      responses:
+        '200':
+          description: Returns response
+          content:
+            application/xml:
+              schema:
+                $ref: '#/components/schemas/test'
+components:
+  schemas:
+    test:
+      type: object
+      properties:
+        a:
+          type: string
+        b:
+          type: integer
+        c:
+          oneOf:
+            - type: object
+            - type: array
+              items:
+                type: string
+            - type: boolean
+            - type: integer
+            - type: number

test/e2e-cypress/static/documents/bugs/6540.yaml

@@ -0,0 +1,85 @@
+openapi: 3.0.0
+info:
+  description: Test API
+  version: v1
+  title: Test API
+tags:
+  - name: Test
+    description: Test API
+servers:
+  - url: /v1
+paths:
+  /test:
+    post:
+      tags:
+        - Test
+      summary: Test endpoint
+      description: Test
+      operationId: postTest
+      responses:
+        '200':
+          description: Returns response
+          content:
+            application/xml:
+              schema:
+                $ref: '#/components/schemas/test'
+components:
+  schemas:
+    test:
+      type: object
+      properties:
+        a:
+          type: string
+        b:
+          type: integer
+        c:
+          type: array
+          items:
+            $ref: '#/components/schemas/Things'
+        d:
+          type: array
+          items:
+            anyOf:
+              - $ref: '#/components/schemas/TextObject'
+              - $ref: '#/components/schemas/ImageObject'
+
+
+    Things:
+      type: object
+      oneOf:
+        - $ref: '#/components/schemas/TextObject'
+        - $ref: '#/components/schemas/ImageObject'
+
+    TextObject:
+      required:
+        - data
+      type: object
+      properties:
+        objectType:
+          type: string
+          example: Text
+          xml:
+            name: ObjectType
+        data:
+          type: string
+          example: This is a text
+          xml:
+            name: Data
+      description: Contains a text
+
+    ImageObject:
+      required:
+        - data
+      type: object
+      properties:
+        objectType:
+          type: string
+          example: image
+          xml:
+            name: ObjectType
+        data:
+          type: string
+          example: This is a image
+          xml:
+            name: Data
+      description: Contains a image

test/e2e-cypress/tests/bugs/4943.js

@@ -0,0 +1,20 @@
+describe("#4943: XML example not rendered correctly with oneOf", () => {
+  it("should render integer property correctly", () => {
+    cy
+      .visit("/?url=/documents/bugs/4943.yaml")
+      .get("#operations-Test-postTest")
+      .click()
+      .get(".microlight")
+      .contains("<b>0</b>")
+  })
+  it("should render oneOf property correctly", () => {
+    cy
+      .visit("/?url=/documents/bugs/4943.yaml")
+      .get("#operations-Test-postTest")
+      .click()
+      .get(".try-out__btn")
+      .click()
+      .get(".microlight")
+      .contains("<c>\n\t</c>")
+  })
+})

test/e2e-cypress/tests/bugs/6540.js

@@ -0,0 +1,11 @@
+describe("#6540: XML example not rendered correctly with oneOf", () => {
+  it("should render xml like json", () => {
+    const expected = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<test>\n\t<a>string</a>\n\t<b>0</b>\n\t<c>\n\t\t<ObjectType>Text</ObjectType>\n\t\t<Data>This is a text</Data>\n\t</c>\n\t<c>\n\t\t<ObjectType>image</ObjectType>\n\t\t<Data>This is a image</Data>\n\t</c>\n\t<d>\n\t\t<ObjectType>Text</ObjectType>\n\t\t<Data>This is a text</Data>\n\t</d>\n\t<d>\n\t\t<ObjectType>image</ObjectType>\n\t\t<Data>This is a image</Data>\n\t</d>\n</test>"
+    cy
+      .visit("/?url=/documents/bugs/6540.yaml")
+      .get("#operations-Test-postTest")
+      .click()
+      .get(".microlight")
+      .contains(expected)
+  })
+})