openapi-generator-maven-plugin generates invalid Java code when using "oneOf:" property

[R4NN-BAE]

Description

Maven test target in openapi-generator-maven-plugin will run successfully,
but the generated Java models are not valid Java code and cannot be compiled by Java compiler
and therefore cannot be used as a JavaClient.
Because of the following issues in the generated Java model Value.java:

Array.validateJsonObject(jsonObject); // The method validateJsonObject(JsonObject) is undefined for the type Array

Is the generated Java code in the maven test target not validate by a Java compiler?
Note, the same error can be reproduced with the Java Types, String, Boolean, BigDecimal

Steps to reproduce

When using following modified schema in openapi\modules\openapi-generator-maven-plugin\src\test\resources\petstore-on-classpath.yaml

openapi: 3.0.0
servers:
  - url: 'http://petstore.swagger.io/v2'
info:
  description: >-
    This is a sample server Petstore server. For this sample, you can use the api key
    `special-key` to test the authorization
  version: 1.0.0
  title: OpenAPI Petstore
  license:
    name: Apache-2.0
    url: 'https://www.apache.org/licenses/LICENSE-2.0.html'
...
paths: 
  /values:  
    get:  
      tags:  
        - values  
      summary: Get some primitive values  
      description: ''  
      operationId: getSomeValues  
      responses:  
        '200':  
          description: successful operation  
          content:  
            application/json:  
              schema:  
                $ref: '#/components/schemas/Value'  
        '400':  
          description: Invalid Value  
...

schemas:  
    Value:  
      description: Value datatype  
      oneOf:  
        - $ref: "#/components/schemas/Scalar"  
        - $ref: "#/components/schemas/Array"  
    Scalar:  
      description: Scalar datatype  
      oneOf:  
        - type: string  
          maxLength: 1089  
        - type: number  
        - type: boolean  
    Array:  
      type: array  
      minItems: 1  
      items:  
        $ref: "#/components/schemas/Scalar"

And the following modified openapi\modules\openapi-generator-maven-plugin\pom.xml,
the <library>jersey2</library> was removed.

 <configuration>
                    <inputSpec>petstore-on-classpath.yaml</inputSpec>
                    <generatorName>java</generatorName>

                    <skipIfSpecIsUnchanged>true</skipIfSpecIsUnchanged>

                    <configOptions>
                        <dateLibrary>joda</dateLibrary>
                    </configOptions>
                    <output>${basedir}/target/generated-sources/common-maven/remote-openapi</output>
                    <apiPackage>remote.org.openapitools.client.api</apiPackage>
                    <modelPackage>remote.org.openapitools.client.model</modelPackage>
                    <invokerPackage>remote.org.openapitools.client</invokerPackage>
</configuration>

openapi-generator version

Can be reproduced with the current "Master" version of this repository.
But also the compile error was reproduced on a build server with the openapi-generator-maven-plugin:

<!-- RELEASE_VERSION -->
<version>6.0.0</version>
<!-- /RELEASE_VERSION -->

Suggest a fix

Maybe there should be a more strict check in this code section,

openapi-generator/modules/openapi-generator/src/main/resources/Java/libraries/okhttp-gson/oneof_model.mustache

Lines 101 to 123 in 69f79fb

	{{#oneOf}}
	// deserialize {{{.}}}
	try {
	// validate the JSON object to see if any exception is thrown
	{{.}}.validateJsonObject(jsonObject);
	actualAdapter = adapter{{.}};
	match++;
	log.log(Level.FINER, "Input data matches schema '{{{.}}}'");
	} catch (Exception e) {
	// deserialization failed, continue
	errorMessages.add(String.format("Deserialization for {{{.}}} failed with `%s`.", e.getMessage()));
	log.log(Level.FINER, "Input data does not match schema '{{{.}}}'", e);
	}
	{{/oneOf}}
	if (match == 1) {
	{{classname}} ret = new {{classname}}();
	ret.setActualInstance(actualAdapter.fromJsonTree(jsonObject));
	return ret;
	}
	throw new IOException(String.format("Failed deserialization for {{classname}}: %d classes match result, expected 1. Detailed failure message for oneOf schemas: %s. JSON: %s", match, errorMessages, jsonObject.toString()));
	}

It looks like this would generate .validateJsonObject(jsonObject) on every type which is not valid
for type Array, String, Boolean, BigDecimal in Java.

[premnalla]

I'm having the same issue with DigitalOceans's API - https://github.com/digitalocean/openapi

$openapi-generator --version
openapi-generator-cli 6.0.0
commit : 69f79fb
built : 2022-05-26T02:54:15Z
source : https://github.com/openapitools/openapi-generator
docs : https://openapi-generator.tech/

[lalitmathwani]

+1 seeing this issue with 6.0.0 as well on one of our internal apis @ adobe.

[autumoswitzerland]

The same here with:

Command: openapi-generator-cli generate -i SWIFT-API-swift-banking-premium-1.1.2-swagger.yaml -g java -o out

YAML:

https://developer.swift.com/sites/default/files/specs/SWIFT-API-swift-banking-premium-1.1.2-swagger.yaml

I didn't specify any specific property and I got the code:

...
// deserialize Object
try {
// validate the JSON object to see if any exception is thrown
Object.validateJsonObject(jsonObject);
actualAdapter = adapterObject;
match++;
log.log(Level.FINER, "Input data matches schema 'Object'");
...

[aruvic]

+1 seeing this issue with 6.1.0 as well on one of our internal apis

[aruvic]

@wing328 Hi William, please can you prioritize this bug for 6.2.1. I'm trying to read the code and fix it myself but the code base is huge and I still don't get how things work :-)

[Santobert]

It is not only oneOf that is affected. I have the same problem with anyOf. I assume this will gain relevance since swagger-api/swagger-core#4291 was merged.

[StevenArzt]

We also have this issue with one of our builds running openapi-generator-maven-plugin in version 6.2.1, which is the most recent one. The issue affects Boolean, Double, Float, Integer, Long, String. It would be great if this bug could be fixed very soon.

[karzang]

In #13897 I provided a potential fix for this problem regarding oneOf. I think this PR would also be a good baseline for fixing the same problem concerning anyOf.

[felicamargo]

I am experiencing the same problem with Fireblocks API, @StevenArzt it also affects BigDecimal, on top of the other classes you listed.
error: cannot find symbol
[ERROR] symbol: method validateJsonObject(JsonObject)
[ERROR] location: class BigDecimal

[lostiniceland]

Same here with 6.2.1
We are seing an LocalDate.validateJsonObject(... which is completely bogus. It seems to be cause by an allOf in this case

[tstuber]

Is there a known workaround for this issue?

[karzang]

I think a workaround would be to wrap your Boolean, Double, Float, Integer, Long, String or LocalDate Schema into an Object and then reference the object in your allOf/anyOf/oneOf