Fix selection of unnecessary form parameter models (#16418)

* fix idea

* add unit test

* adjust warnings about form parameters

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

@@ -6928,6 +6928,13 @@ public class DefaultCodegen implements CodegenConfig {
         LOGGER.debug("debugging fromRequestBodyToFormParameters= {}", body);
         Schema schema = ModelUtils.getSchemaFromRequestBody(body);
         schema = ModelUtils.getReferencedSchema(this.openAPI, schema);
+        if(ModelUtils.isMapSchema(schema)) {
+            LOGGER.error("Form parameters with additionalProperties are not supported by OpenAPI Generator. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
+        }
+        if(ModelUtils.isArraySchema(schema)) {
+            LOGGER.error("Array form parameters are not supported by OpenAPI Generator. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
+        }
+
         List<String> allRequired = new ArrayList<>();
         Map<String, Schema> properties = new LinkedHashMap<>();
         // this traverses a composed schema and extracts all properties in each schema into properties
@@ -6943,10 +6950,6 @@ public class DefaultCodegen implements CodegenConfig {
                 // value => property schema
                 String propertyName = entry.getKey();
                 Schema propertySchema = entry.getValue();
-                if (ModelUtils.isMapSchema(propertySchema)) {
-                    LOGGER.error("Map of form parameters not supported. Please report the issue to https://github.com/openapitools/openapi-generator if you need help.");
-                    continue;
-                }
                 codegenParameter = fromFormProperty(propertyName, propertySchema, imports);
 
                 // Set 'required' flag defined in the schema element

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

@@ -367,7 +367,7 @@ public class ModelUtils {
         Map<String, Schema> properties = schema.getProperties();
         if (properties != null) {
             for (Schema property : properties.values()) {
-                visitSchema(openAPI, property, mimeType, visitedSchemas, visitor);
+                visitSchema(openAPI, property, null, visitedSchemas, visitor);
             }
         }
     }

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

@@ -113,6 +113,14 @@ public class ModelUtilsTest {
         Assert.assertTrue(unusedSchemas.contains("SomeObj7"), "contains 'SomeObj7'");
     }
 
+    @Test
+    public void testNestedFormParameter() {
+        final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/2_0/nestedFormParameter.yaml");
+        List<String> unusedSchemas = ModelUtils.getSchemasUsedOnlyInFormParam(openAPI);
+        Assert.assertEquals(unusedSchemas.size(), 1);
+        Assert.assertTrue(unusedSchemas.contains("OuterObject"), "contains 'OuterObject'");
+    }
+
     @Test
     public void testNoComponentsSection() {
         final OpenAPI openAPI = TestUtils.parseFlattenSpec("src/test/resources/3_0/ping.yaml");

modules/openapi-generator/src/test/resources/2_0/nestedFormParameter.yaml

@@ -0,0 +1,28 @@
+swagger: "2.0"
+info:
+  title: dummy
+  version: dummy
+paths:
+  /property:
+    post:
+      consumes:
+        - application/x-www-form-urlencoded
+      parameters:
+        - in: body
+          name: body
+          schema:
+              $ref: '#/definitions/OuterObject'
+      responses:
+        '200':
+          description: dummy
+definitions:
+  InnerObject:
+    type: object
+    properties:
+      innerProperty:
+        type: string
+  OuterObject:
+    type: object
+    properties:
+      outerProperty:
+        $ref: '#/definitions/InnerObject'