[JAVA] Generate client files with multiple enum oneOf types (#12687)

* handle multiple enum types for oneof

* add updates from generate-samples.sh

* add test coverage for oneof enum generation

* update doc and var names for clarity

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

@@ -2736,7 +2736,9 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
                         addProperties(allProperties, allRequired, refSchema, new HashSet<>());
                     } else {
                         // composition
-                        addProperties(properties, required, refSchema, new HashSet<>());
+                        Map<String, Schema> newProperties = new LinkedHashMap<>();
+                        addProperties(newProperties, required, refSchema, new HashSet<>());
+                        mergeProperties(properties, newProperties);
                         addProperties(allProperties, allRequired, refSchema, new HashSet<>());
                     }
                 }
@@ -2812,6 +2814,28 @@ protected void updateModelForComposedSchema(CodegenModel m, Schema schema, Map<S
         // end of code block for composed schema
     }
 
+    /**
+     * Combines all previously-detected type entries for a schema with newly-discovered ones, to ensure
+     * that schema for items like enum include all possible values.
+     */
+    private void mergeProperties(Map<String, Schema> existingProperties, Map<String, Schema> newProperties) {
+        // https://github.com/OpenAPITools/openapi-generator/issues/12545
+        if (null != existingProperties && null != newProperties) {
+            Schema existingType = existingProperties.get("type");
+            Schema newType = newProperties.get("type");
+            existingProperties.putAll(newProperties);
+            if (null != existingType && null != newType && !newType.getEnum().isEmpty()) {
+                for (Object e : newType.getEnum()) {
+                    // ensure all interface enum types are added to schema
+                    if (null != existingType.getEnum() && !existingType.getEnum().contains(e)) {
+                        existingType.addEnumItemObject(e);
+                    }
+                }
+                existingProperties.put("type", existingType);
+            }
+        }
+    }
+
     protected void updateModelForObject(CodegenModel m, Schema schema) {
         if (schema.getProperties() != null || schema.getRequired() != null && !(schema instanceof ComposedSchema)) {
             // passing null to allProperties and allRequired as there's no parent

modules/openapi-generator/src/test/java/org/openapitools/codegen/DefaultCodegenTest.java

@@ -640,6 +640,36 @@ public void testGetSchemaTypeWithComposedSchemaWithOneOf() {
         Assert.assertEquals(type, "oneOf<ObjA,ObjB>");
     }
 
+    @Test
+    public void testOneOfEnum() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/issue12545.json");
+        final DefaultCodegen codegen = new DefaultCodegen();
+        String modelName = "petItems";
+
+        final Schema schema = openAPI.getComponents().getSchemas().get(modelName);
+        codegen.setOpenAPI(openAPI);
+        CodegenModel petItems = codegen.fromModel(modelName, schema);
+
+        Set<String> oneOf = new TreeSet<String>();
+        oneOf.add("Dog");
+        oneOf.add("Cat");
+        Assert.assertEquals(petItems.oneOf, oneOf);
+        // make sure that animal has the property type
+        boolean typeSeen = false;
+        boolean typeContainsEnums = false;
+        for (CodegenProperty cp : petItems.vars) {
+            if ("type".equals(cp.name)) {
+                typeSeen = true;
+                if (null != cp.get_enum() && cp.get_enum().contains("dog") && cp.get_enum().contains("cat")) {
+                    typeContainsEnums = true;
+                }
+                break;
+            }
+        }
+        Assert.assertTrue(typeSeen);
+        Assert.assertTrue(typeContainsEnums);
+    }
+
     @Test
     public void testComposedSchemaOneOfWithProperties() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/oneOf.yaml");

modules/openapi-generator/src/test/resources/3_0/issue12545.json

@@ -0,0 +1,73 @@
+{
+  "openapi": "3.0.1",
+  "info": {
+    "version": "1.0.0",
+    "title": "OpenAPI Petstore"
+  },
+  "paths": {
+    "/": {
+      "get": {
+        "description": "get all pets in a household",
+        "responses": {
+          "200": {
+            "description": "successful operation",
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/Household"
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  },
+  "components": {
+    "schemas": {
+      "Household": {
+        "title": "Household",
+        "type" : "object",
+        "required": [
+          "pets"
+        ],
+        "properties": {
+          "pets": {
+            "type": "array",
+            "title": "pets",
+            "items" : {
+              "title": "petItems",
+              "oneOf" : [ {
+                "$ref" : "#/components/schemas/Dog"
+              }, {
+                "$ref" : "#/components/schemas/Cat"
+              } ]
+            }
+          }
+        }
+      },
+      "Dog": {
+        "type" : "object",
+        "title": "Dog",
+        "properties" : {
+          "type" : {
+            "type" : "string",
+            "enum" : [ "dog" ]
+          }
+        },
+        "required" : [ "type" ]
+      },
+      "Cat": {
+        "type" : "object",
+        "title": "Cat",
+        "properties" : {
+          "type" : {
+            "type" : "string",
+            "enum" : [ "cat" ]
+          }
+        },
+        "required" : [ "type" ]
+      }
+    }
+  }
+}