Fix null check in 3.1 spec

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

@@ -890,7 +890,7 @@ public boolean isNullTypeSchema(Schema schema) {
 
         if (schema.getTypes() != null && !schema.getTypes().isEmpty()) {
             // 3.1 spec
-            if (schema.getTypes().size() ==1) { // 1 type only
+            if (schema.getTypes().size() == 1) { // 1 type only
                 String type = (String) schema.getTypes().iterator().next();
                 return type == null || "null".equals(type);
             } else { // more than 1 type so must not be just null
@@ -902,6 +902,11 @@ public boolean isNullTypeSchema(Schema schema) {
             if (Boolean.TRUE.equals(schema.getNullable())) {
                 return true;
             }
+
+            // for `type: null`
+            if (schema.getTypes() == null && schema.get$ref() == null) {
+                return true;
+            }
         } else { // 3.0.x or 2.x spec
             if ((schema.getType() == null || schema.getType().equals("null")) && schema.get$ref() == null) {
                 return true;
@@ -938,7 +943,7 @@ private Schema processSimplifyOneOf(Schema schema) {
             if (oneOfSchemas.size() == 6) {
                 TreeSet<String> ts = new TreeSet<>();
                 for (Schema s: oneOfSchemas) {
-                    ts.add(s.getType());
+                    ts.add(ModelUtils.getType(s));
                 }
 
                 if (ts.equals(anyTypeTreeSet)) {
@@ -1063,7 +1068,7 @@ private Schema processSimplifyAnyOf(Schema schema) {
             if (anyOfSchemas.size() == 6) {
                 TreeSet<String> ts = new TreeSet<>();
                 for (Schema s: anyOfSchemas) {
-                    ts.add(s.getType());
+                    ts.add(ModelUtils.getType(s));
                 }
 
                 if (ts.equals(anyTypeTreeSet)) {

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

@@ -2126,6 +2126,25 @@ public static boolean hasAnyOf(Schema schema) {
         return false;
     }
 
+    /**
+     * Returns schema type.
+     * For 3.1 spec, return the first one.
+     *
+     * @param schema the schema
+     * @return schema type
+     */
+    public static String getType(Schema schema) {
+        if (schema == null) {
+            return null;
+        }
+
+        if (schema instanceof JsonSchema) {
+            return String.valueOf(schema.getTypes().iterator().next());
+        } else {
+            return schema.getType();
+        }
+    }
+
     /**
      * Returns true if any of the common attributes of the schema (e.g. readOnly, default, maximum, etc) is defined.
      *

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

@@ -158,6 +158,10 @@ public void testOpenAPINormalizerSimplifyOneOfAnyOf() {
         assertEquals(schema2.getOneOf().size(), 4);
         assertNull(schema2.getNullable());
 
+        Schema schema2b = openAPI.getComponents().getSchemas().get("OneOfTest2");
+        assertEquals(schema2b.getOneOf().size(), 2);
+        assertNull(schema2b.getNullable());
+
         Schema schema5 = openAPI.getComponents().getSchemas().get("OneOfNullableTest");
         assertEquals(schema5.getOneOf().size(), 3);
         assertNull(schema5.getNullable());
@@ -189,6 +193,11 @@ public void testOpenAPINormalizerSimplifyOneOfAnyOf() {
         assertTrue(schema4 instanceof IntegerSchema);
         assertTrue(schema4.getNullable());
 
+        Schema schema4b = openAPI.getComponents().getSchemas().get("OneOfTest2");
+        assertNull(schema4b.getOneOf());
+        assertTrue(schema4b instanceof StringSchema);
+        assertTrue(schema4b.getNullable());
+
         Schema schema6 = openAPI.getComponents().getSchemas().get("OneOfNullableTest");
         assertEquals(schema6.getOneOf().size(), 2);
         assertTrue(schema6.getNullable());
@@ -532,7 +541,7 @@ public void testSetContainerToNullable() {
     @Test
     public void testSetPrimitiveTypesToNullable() {
         // test `string|integer|number|boolean`
-        OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0//setPrimitiveTypesToNullable_test.yaml");
+        OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_0/setPrimitiveTypesToNullable_test.yaml");
 
         Schema schema = openAPI.getComponents().getSchemas().get("Person");
         assertEquals(((Schema) schema.getProperties().get("lastName")).getNullable(), null);
@@ -552,7 +561,7 @@ public void testSetPrimitiveTypesToNullable() {
         assertEquals(((Schema) schema2.getProperties().get("first_boolean")).getNullable(), true);
 
         // test `number` only
-        OpenAPI openAPI2 = TestUtils.parseSpec("src/test/resources/3_0//setPrimitiveTypesToNullable_test.yaml");
+        OpenAPI openAPI2 = TestUtils.parseSpec("src/test/resources/3_0/setPrimitiveTypesToNullable_test.yaml");
 
         Schema schema3 = openAPI2.getComponents().getSchemas().get("Person");
         assertEquals(((Schema) schema3.getProperties().get("lastName")).getNullable(), null);
@@ -572,7 +581,7 @@ public void testSetPrimitiveTypesToNullable() {
     }
 
     @Test
-    public void testOpenAPINormalizerSimplifyOneOfAnyOf31Spec() {
+    public void testOpenAPINormalizerSimplifyOneOfAnyOf31SpecForIssue18184  () {
         // to test the rule SIMPLIFY_ONEOF_ANYOF in 3.1 spec
         OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_1/issue_18184.yaml");
         // test spec contains anyOf with a ref to enum and another scheme type is null
@@ -636,6 +645,77 @@ public void testOpenAPINormalizerProcessingArraySchema31Spec() {
         assertEquals(((Schema) schema6.getProperties().get("arrayOfStrings")).getItems().getTypes().contains("string"), true);
         assertEquals(((Schema) schema6.getProperties().get("arrayOfStrings")).getItems().getType(), "string");
         assertEquals(((Schema) schema6.getProperties().get("arrayOfStrings")).getType(), "array");
+    }
+
+    @Test
+    public void testOpenAPINormalizerSimplifyOneOfAnyOf31Spec() {
+        // to test the rule SIMPLIFY_ONEOF_ANYOF with 3.1 spec
+        OpenAPI openAPI = TestUtils.parseSpec("src/test/resources/3_1/simplifyOneOfAnyOf_test.yaml");
+
+        Schema schema = openAPI.getComponents().getSchemas().get("AnyOfTest");
+        assertEquals(schema.getAnyOf().size(), 4);
+        assertNull(schema.getNullable());
+
+        Schema schema2 = openAPI.getComponents().getSchemas().get("OneOfTest");
+        assertEquals(schema2.getOneOf().size(), 4);
+        assertNull(schema2.getNullable());
+
+        Schema schema2b = openAPI.getComponents().getSchemas().get("OneOfTest2");
+        assertEquals(schema2b.getOneOf().size(), 2);
+        assertNull(schema2b.getNullable());
+
+        Schema schema5 = openAPI.getComponents().getSchemas().get("OneOfNullableTest");
+        assertEquals(schema5.getOneOf().size(), 3);
+        assertNull(schema5.getNullable());
+
+        Schema schema7 = openAPI.getComponents().getSchemas().get("Parent");
+        assertEquals(((Schema) schema7.getProperties().get("number")).getAnyOf().size(), 1);
+
+        Schema schema9 = openAPI.getComponents().getSchemas().get("AnyOfStringArrayOfString");
+        assertEquals(schema9.getAnyOf().size(), 2);
+
+        Schema schema11 = openAPI.getComponents().getSchemas().get("AnyOfAnyType");
+        assertEquals(schema11.getAnyOf().size(), 6);
+
+        Schema schema13 = openAPI.getComponents().getSchemas().get("OneOfAnyType");
+        assertEquals(schema13.getOneOf().size(), 6);
 
+        Map<String, String> options = new HashMap<>();
+        options.put("SIMPLIFY_ONEOF_ANYOF", "true");
+        OpenAPINormalizer openAPINormalizer = new OpenAPINormalizer(openAPI, options);
+        openAPINormalizer.normalize();
+
+        Schema schema3 = openAPI.getComponents().getSchemas().get("AnyOfTest");
+        assertNull(schema3.getAnyOf());
+        assertEquals(ModelUtils.getType(schema3), "string");
+        assertTrue(schema3.getNullable());
+
+        Schema schema4 = openAPI.getComponents().getSchemas().get("OneOfTest");
+        assertNull(schema4.getOneOf());
+        assertEquals(ModelUtils.getType(schema4), "integer");
+        assertTrue(schema4.getNullable());
+
+        Schema schema4b = openAPI.getComponents().getSchemas().get("OneOfTest2");
+        assertNull(schema4b.getOneOf());
+        assertEquals(ModelUtils.getType(schema4b), "string");
+        assertTrue(schema4b.getNullable());
+
+        Schema schema6 = openAPI.getComponents().getSchemas().get("OneOfNullableTest");
+        assertEquals(schema6.getOneOf().size(), 2);
+        assertTrue(schema6.getNullable());
+
+        Schema schema8 = openAPI.getComponents().getSchemas().get("Parent");
+        assertEquals(((Schema) schema8.getProperties().get("number")).get$ref(), "#/components/schemas/Number");
+
+        Schema schema10 = openAPI.getComponents().getSchemas().get("AnyOfStringArrayOfString");
+        assertEquals(schema10.getAnyOf().size(), 2);
+
+        Schema schema12 = openAPI.getComponents().getSchemas().get("AnyOfAnyType");
+        assertEquals(schema12.getAnyOf(), null);
+        assertEquals(schema12.getType(), null);
+
+        Schema schema14 = openAPI.getComponents().getSchemas().get("OneOfAnyType");
+        assertEquals(schema14.getOneOf(), null);
+        assertEquals(schema14.getType(), null);
     }
 }

modules/openapi-generator/src/test/resources/3_0/simplifyOneOfAnyOf_test.yaml

@@ -40,6 +40,11 @@ components:
         - type: 'null'
         - type: null
         - $ref: null
+    OneOfTest2:
+      description: to test oneOf
+      oneOf:
+        - type: string
+        - type: 'null'
     OneOfNullableTest:
       description: to test oneOf nullable
       oneOf:

modules/openapi-generator/src/test/resources/3_1/simplifyOneOfAnyOf_test.yaml

@@ -0,0 +1,114 @@
+openapi: 3.1.0
+info:
+  version: 1.0.0
+  title: Example
+  license:
+    name: MIT
+servers:
+  - url: http://api.example.xyz/v1
+paths:
+  /person/display/{personId}:
+    get:
+      parameters:
+        - name: personId
+          in: path
+          required: true
+          description: The id of the person to retrieve
+          schema:
+            type: string
+      operationId: list
+      responses:
+        '200':
+          description: OK
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/AnyOfTest"
+components:
+  schemas:
+    AnyOfTest:
+      description: to test anyOf
+      anyOf:
+        - type: string
+        - type: 'null'
+        - type: null
+        - $ref: null
+    OneOfTest:
+      description: to test oneOf
+      oneOf:
+        - type: integer
+        - type: 'null'
+        - type: null
+        - $ref: null
+    OneOfTest2:
+      description: to test oneOf
+      oneOf:
+        - type: string
+        - type: 'null'
+    OneOfNullableTest:
+      description: to test oneOf nullable
+      oneOf:
+        - type: integer
+        - type: string
+        - $ref: null
+    SingleAnyOfTest:
+      description: to test anyOf (enum string only)
+      anyOf:
+        - type: string
+          enum:
+            - A
+            - B
+    Parent:
+      type: object
+      properties:
+        number:
+          anyOf:
+            - $ref: '#/components/schemas/Number'
+    ParentWithOneOfProperty:
+      type: object
+      properties:
+        number:
+          oneOf:
+            - $ref: '#/components/schemas/Number'
+    ParentWithPluralOneOfProperty:
+      type: object
+      properties:
+        number:
+          oneOf:
+            - $ref: '#/components/schemas/Number'
+            - $ref: '#/components/schemas/Number2'
+    Number:
+      enum:
+        - one
+        - two
+        - three
+      type: string
+    Number2:
+      enum:
+        - one
+        - two
+      type: string
+    AnyOfStringArrayOfString:
+      anyOf:
+        - type: string
+        - type: array
+          items:
+            type: string
+    AnyOfAnyType:
+      anyOf:
+        - type: boolean
+        - type: array
+          items: {}
+        - type: object
+        - type: string
+        - type: number
+        - type: integer
+    OneOfAnyType:
+      oneOf:
+        - type: object
+        - type: boolean
+        - type: number
+        - type: string
+        - type: integer
+        - type: array
+          items: {}