[BUG] PHP Symfony if the application/x-www-form-urlencoded content type is used, then all object properties specified in the snake_case in the controller are getting from the request in camelCase

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?

Description

if the application/x-www-form-urlencoded content type is used, then all object properties specified in the sneak_case in the controller are getting from the request in camelCase. This breaks the contract with the frontend and the parameters that were sent according to it in sneak_case are always null .

openapi-generator version

5.0.0 and latest

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: test sneak_case issue
  description: |-
    test sneak_case issue
  version: "1.0"

paths:
  /register/:
    post:
      description: |-
        test sneak_case issue
      requestBody:
        content:
          application/x-www-form-urlencoded:
            schema:
              $ref: '#/components/schemas/RegistrationRequest'
        required: true
      responses:
        200:
          description: OK

components:
  schemas:
    RegistrationRequest:
      type: object
      required:
        - first_name
        - last_name
      properties:
        first_name:
          type: string
        last_name:
          type: string

Generation Details

Generation method:

docker run --rm -v "/$dir:/local" openapitools/openapi-generator-cli:latest generate \
    -i local/contract/sneak_issue_test.yaml \
    -g php-symfony

    public function registerPostAction(Request $request)
    {
        // Handle authentication

        // Read out all input parameter values into variables
        $firstName = $request->request->get('firstName');
        $lastName = $request->request->get('lastName');

        // Use the default value if no value was provided

        // Deserialize the input values that needs it
        try {
            $firstName = $this->deserialize($firstName, 'string', 'string');
            $lastName = $this->deserialize($lastName, 'string', 'string');
        } catch (SerializerRuntimeException $exception) {
            return $this->createBadRequestResponse($exception->getMessage());
        }

        // Validate the input values
        $asserts = [];
        $asserts[] = new Assert\NotNull();
        $asserts[] = new Assert\Type("string");
        $response = $this->validate($firstName, $asserts);
        if ($response instanceof Response) {
            return $response;
        }
        $asserts = [];
        $asserts[] = new Assert\NotNull();
        $asserts[] = new Assert\Type("string");
        $response = $this->validate($lastName, $asserts);
        if ($response instanceof Response) {
            return $response;
        }


        try {
            $handler = $this->getApiHandler();


            // Make the call to the business logic
            $responseCode = 204;
            $responseHeaders = [];
            $result = $handler->registerPost($firstName, $lastName, $responseCode, $responseHeaders);

            // Find default response message
            $message = '';

            // Find a more specific message, if available
            switch ($responseCode) {
                case 200:
                    $message = 'OK';
                    break;
            }

            return new Response(
                '',
                $responseCode,
                array_merge(
                    $responseHeaders,
                    [
                        'X-OpenAPI-Message' => $message
                    ]
                )
            );
        } catch (Exception $fallthrough) {
            return $this->createErrorResponse(new HttpException(500, 'An unsuspected error occurred.', $fallthrough));
        }
    }

Steps to reproduce

1. Generate a Symfony controller according to the presented Open Api configuration

Related issues/PRs

Suggest a fix

I know about the variableNamingConvention parameter, but then all the variables in the code and models become in the snake_case. I would like to be able to get parameters from the form in the snake_case to the camelCase variable
example:

        // Read out all input parameter values into variables
        $firstName = $request->request->get('first_name');
        $lastName = $request->request->get('last_name');

Start by running the provided OpenAPI declaration through the dockerized php-symfony generator and inspect the generated registerPostAction request reads. Compare the generated parameter names with the snake_case form fields, then verify that the generated controller retrieves first_name and last_name correctly without changing the broader variable naming convention.