use_allof_for_refs: extend to example field

Author: Igor Tsiglyar

protoc-gen-openapiv2/internal/genopenapi/template.go

@@ -522,13 +522,16 @@ func renderMessageAsDefinition(msg *descriptor.Message, reg *descriptor.Registry
 			if fieldSchema.Ref != "" {
 				// Per the JSON Reference syntax: Any members other than "$ref" in a JSON Reference object SHALL be ignored.
 				// https://tools.ietf.org/html/draft-pbryan-zyp-json-ref-03#section-3
-				// However, use allOf to specify Title/Description/readOnly fields.
-				if fieldSchema.Title != "" || fieldSchema.Description != "" || fieldSchema.ReadOnly {
+				// However, use allOf to specify Title/Description/Example/readOnly fields.
+				if fieldSchema.Title != "" || fieldSchema.Description != "" || len(fieldSchema.Example) > 0 || fieldSchema.ReadOnly {
 					fieldSchema = openapiSchemaObject{
 						Title:       fieldSchema.Title,
 						Description: fieldSchema.Description,
-						ReadOnly:    fieldSchema.ReadOnly,
-						AllOf:       []allOfEntry{{Ref: fieldSchema.Ref}},
+						schemaCore: schemaCore{
+							Example: fieldSchema.Example,
+						},
+						ReadOnly: fieldSchema.ReadOnly,
+						AllOf:    []allOfEntry{{Ref: fieldSchema.Ref}},
 					}
 				} else {
 					fieldSchema = openapiSchemaObject{schemaCore: schemaCore{Ref: fieldSchema.Ref}}