[JAVA][SPRING] Bug generating multipart file array for RestAssured library

Description

When generating the Api class for RestAssured and creating methods for composing and adding data to the RequestSpecBuilder, the generated method for adding a list of files (List<java.io.File>) to the reqSpec creates code that is unable to compile.

The generated code tries to pass the list directly to reqSpec.addMultiPart(java.io.File file) which only accepts a single file.

openapi-generator version

4.3.1

OpenAPI declaration file content or url

openapi: 3.0.1
info:
  title: foo-api
  description: RESTful API exposing services used for foo
  version: 1.0.0
paths:
  /foo/upload:
    post:
      operationId: uploadFooFiles
      requestBody:
        required: true
        content:
          multipart/form-data:
            schema:
              properties:
                files:
                  type: array
                  items:
                    type: string
                    format: binary
      responses:
        200:
          description: Success
          content:
            application/json:
              schema:
                type: object
                properties:
                  code:
                    type: integer
                  message:
                    type: string

Command line used for generation

Java version: 11.0.7-amzn
Gradle version: 6.8.3

build.gradle:

plugins {
    id "org.openapi.generator" version "4.3.1"
    id "java"
}

dependencies {
    implementation "io.springfox:springfox-swagger2:2.9.0"
    implementation "org.openapitools:jackson-databind-nullable:0.2.1"
    implementation "io.rest-assured:rest-assured:3.1.0"
}

openApiGenerate {
    generatorName = "java"
    inputSpec = "$swaggerSourceFile"
    outputDir = "$swaggerOutputDir"
    configFile = "$swaggerConfigFile"
    configOptions = [
        dateLibrary: "java8"
    ]
    library = "rest-assured"
}

CLI: gradle :openApiGenerate or ./gradlew :openApiGenerate

Steps to reproduce

• Create a Java Spring project with OAS generator
• Add OAS spec attached above
• Add build.gradle file with openApiGenerate task as pasted above
• Call CLI command above: gradle :openApiGenerate
• Inspect the bug in generate RestAssured Api class (method name: filesMultiPart)

Related issues/PRs

Suggest a fix/enhancement

Generated method filesMultiPart should iterate over the list of files, adding each individually:

public UploadFooFilesOper filesMultiPart(List<File> files) {
    for (final File file : files) {
        reqSpec.addMultiPart(file);
    }
    return this;
}

Start by running the Gradle openApiGenerate task with the supplied OpenAPI spec and inspect the generated RestAssured API method filesMultiPart. Compare its handling of List with RequestSpecBuilder.addMultiPart(File), then verify that the generated client compiles and adds each file individually.