fix: Fixed regression with oneOf+discriminator

Author: ranger-ross

modules/openapi-generator/src/main/java/org/openapitools/codegen/utils/ModelUtils.java

@@ -2244,14 +2244,18 @@ public static Schema simplyOneOfAnyOfWithOnlyOneNonNullSubSchema(OpenAPI openAPI
     }
 
     /**
-     * Removes duplicate `oneOf` from a given schema
+     * Removes duplicate `oneOf` from a given schema if it does not also have a discriminator.
      *
      * @param schema Schema
      */
     public static void deduplicateOneOfSchema(Schema<?> schema) {
         if (schema.getOneOf() == null) {
             return;
         }
+        if (schema.getDiscriminator() != null) {
+            return; // Duplicate oneOf are allowed if there is a discriminator that can be used to separate them.
+        }
+
         Set<Schema> deduplicated = new LinkedHashSet<>(schema.getOneOf());
         schema.setOneOf(new ArrayList<>(deduplicated));
     }

samples/client/others/rust/hyper/oneOf-reuseRef/src/models/fruit.rs

@@ -16,6 +16,8 @@ use serde::{Deserialize, Serialize};
 pub enum Fruit {
     #[serde(rename="green_apple")]
     GreenApple(Box<models::Apple>),
+    #[serde(rename="red_apple")]
+    RedApple(Box<models::Apple>),
     #[serde(rename="banana")]
     Banana(Box<models::Banana>),
 }

samples/client/others/rust/reqwest/oneOf-reuseRef/src/models/fruit.rs

@@ -16,6 +16,8 @@ use serde::{Deserialize, Serialize};
 pub enum Fruit {
     #[serde(rename="green_apple")]
     GreenApple(Box<models::Apple>),
+    #[serde(rename="red_apple")]
+    RedApple(Box<models::Apple>),
     #[serde(rename="banana")]
     Banana(Box<models::Banana>),
 }