APITest doesn't compile if the return type is a File

We generate with the generator version 6.1.0 a client rest api (6.0.1 works just fine):
java -jar ./openapi-generator-cli-6.1.0.jar generate -g java -o download/javaClient_6_1 -i downlaod/openapi.json -c download/configJavaClient.json -t downoad/templates/SpringClient --global-property skipFormModel=false
configJavaClient:
{
"title": "Download Service",
"groupId": "example.api.java.client",
"artifactId": "download",
"hideGenerationTimestamp": "false",
"basePackage": "example.client.download",
"apiPackage": "example.client.download.api",
"configPackage": "example.client.downoad.configuration",
"invokerPackage": "example.client.download.api",
"modelPackage": "example.client.download.model",
"useGzipFeature": false,
"booleanGetterPrefix": "is",
"dateLibrary": "java8",
"java8": true,
"interfaceOnly": true,
"library": "resttemplate",
"sourceFolder": "src/main/java",
"useOptional": false,
"withXml": false,
"reactive": false,
"serializableModel": true,
"useTags": true,
"useSpringfox": false,
"useAbstractionForFiles": true
}
Minimal API definition:
{
"openapi": "3.0.3",
"info": {
"title": "Download PDF",
"description": "Download PDF",
"contact": {
"name": "XYZ",
"email": "XYZ"
},
"version": "0.0.1"
},
"paths": {
"/download/{id}": {
"parameters": [
{
"name": "id",
"in": "path",
"description": "document ID",
"example": "1",
"required": true,
"schema": {
"type": "string"
}
}
],
"get": {
"summary": "returns a pdf document",
"description": "returns a pdf document",
"operationId": "download",
"tags": [
"pdfdownload"
],
"responses": {
"200": {
"description": "PDF document",
"content": {
"application/pdf": {
"schema": {
"type": "string",
"format": "binary"
}
}
}
},
"default": {
"description": "error",
"content": {
"application/json": {
"schema": {
"type": "object",
"description": "Error data",
"properties": {
"errorNumber": {
"type": "integer",
"description": "error number.",
"example": 2
}
},
"required": [
"errorNumber"
]
}
}
}
}
}
}
}
},
"components": {
"schemas": {
"ErrorData": {
"type": "object",
"description": "Error data",
"properties": {
"errorNumber": {
"type": "integer",
"description": "error number.",
"example": 2
}
},
"required": [
"errorNumber"
]
}
}
}
}

Generated ApiTest:

@Test
public void downloadTest() {
String authorization = null;
String id = null;

File response = api.download(id);

    // TODO: test validations
}

while the download method returns org.springframework.core.io.Resource. So there is a compile error.

This bug was provided within the commit version fa22ba9dd9932f0a410afb6e8c6bdb9576d2d643 at 22.08.2022. So this commit for it self is totally ok, but the mustache file modules\openapi-generator\src\main\resources\Java\libraries\resttemplate\api_test.mustache needs to be adjusted as well. The line #41:

{{#returnType}}{{{.}}} response = {{/returnType}}api.{{operationId}}({{#allParams}}{{paramName}}{{^-last}}, {{/-last}}{{/allParams}});

got to be replaced by

{{#returnType}}{{#isResponseFile}}{{#useAbstractionForFiles}}org.springframework.core.io.Resource{{/useAbstractionForFiles}}{{^useAbstractionForFiles}}{{{.}}}{{/useAbstractionForFiles}}{{/isResponseFile}}{{^isResponseFile}}{{{.}}}{{/isResponseFile}} response = {{/returnType}}api.{{operationId}}({{#allParams}}{{paramName}}{{^-last}}, {{/-last}}{{/allParams}});

to do the same treatment for the return value as in the generatet api function.

Start with modules/openapi-generator/src/main/resources/Java/libraries/resttemplate/api_test.mustache and compare its return-type handling with the generated API method. Regenerate the minimal Java client using useAbstractionForFiles and verify that the generated ApiTest compiles with the Resource return type.