[Python] handle nullable parameters with None added to allowed_values (#2034)

* handle nullable parameters with None added to allowed_values

* update samples

* spec for testing enum with null/nullable

modules/openapi-generator/src/main/resources/python/model.mustache

@@ -107,7 +107,7 @@ class {{classname}}(object):
 {{/isNullable}}
 {{#isEnum}}
 {{#isContainer}}
-        allowed_values = [{{#allowableValues}}{{#values}}{{#items.isString}}"{{/items.isString}}{{{this}}}{{#items.isString}}"{{/items.isString}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}]  # noqa: E501
+        allowed_values = [{{#isNullable}}None,{{/isNullable}}{{#allowableValues}}{{#values}}{{#items.isString}}"{{/items.isString}}{{{this}}}{{#items.isString}}"{{/items.isString}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}]  # noqa: E501
 {{#isListContainer}}
         if not set({{{name}}}).issubset(set(allowed_values)):
             raise ValueError(
@@ -126,7 +126,7 @@ class {{classname}}(object):
 {{/isMapContainer}}
 {{/isContainer}}
 {{^isContainer}}
-        allowed_values = [{{#allowableValues}}{{#values}}{{#isString}}"{{/isString}}{{{this}}}{{#isString}}"{{/isString}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}]  # noqa: E501
+        allowed_values = [{{#isNullable}}None,{{/isNullable}}{{#allowableValues}}{{#values}}{{#isString}}"{{/isString}}{{{this}}}{{#isString}}"{{/isString}}{{^-last}}, {{/-last}}{{/values}}{{/allowableValues}}]  # noqa: E501
         if {{{name}}} not in allowed_values:
             raise ValueError(
                 "Invalid value for `{{{name}}}` ({0}), must be one of {1}"  # noqa: E501

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

@@ -20,13 +20,18 @@ package org.openapitools.codegen.python;
 import io.swagger.parser.OpenAPIParser;
 import io.swagger.v3.oas.models.OpenAPI;
 import io.swagger.v3.oas.models.Operation;
+import io.swagger.v3.oas.models.media.StringSchema;
 import io.swagger.v3.parser.core.models.ParseOptions;
 import org.openapitools.codegen.CodegenConstants;
 import org.openapitools.codegen.CodegenOperation;
+import org.openapitools.codegen.CodegenProperty;
 import org.openapitools.codegen.languages.PythonClientCodegen;
 import org.testng.Assert;
 import org.testng.annotations.Test;
 
+import java.util.ArrayList;
+import java.util.Arrays;
+
 public class PythonClientCodegenTest {
 
     @Test
@@ -58,6 +63,18 @@ public class PythonClientCodegenTest {
         Assert.assertEquals(codegen.isHideGenerationTimestamp(), false);
     }
 
+    @Test(description = "test enum null/nullable patterns")
+    public void testEnumNull() {
+        final OpenAPI openAPI = new OpenAPIParser()
+                .readLocation("src/test/resources/3_0/issue_1997.yaml", null, new ParseOptions()).getOpenAPI();
+
+
+        StringSchema prop = (StringSchema) openAPI.getComponents().getSchemas().get("Type").getProperties().get("prop");
+        ArrayList<Object> expected = new ArrayList<>(Arrays.asList("A", "B", "C"));
+        assert prop.getNullable();
+        assert prop.getEnum().equals(expected);
+    }
+
     @Test(description = "test regex patterns")
     public void testRegularExpressionOpenAPISchemaVersion3() {
         final OpenAPI openAPI = new OpenAPIParser()

modules/openapi-generator/src/test/resources/3_0/issue_1997.yaml

@@ -0,0 +1,23 @@
+openapi: 3.0.1
+paths:
+  /test:
+    summary: test
+info:
+  description: test
+  version: 1.0.0
+  title: test
+components:
+  schemas:
+    Type:
+      properties:
+        prop:
+          nullable: true
+          enum: [A, B, C]
+          type: string
+        prop2:
+          enum: [A, B, C, null]
+          type: string
+        prop3:
+          nullable: true
+          enum: []
+          type: string