[BUG] [php] [php-nextgen] Cannot redeclare getModelName

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator?
• 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?
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Description

Models that contain a model_name field generate a duplicate getModelName function.
One is generated for getting the value from the actual field and one is generated for the ModelInterface.

openapi-generator version

Tested version v7.22.0 and master at revision 170778aa04dd372b05facfd2c504afe8d21cd1d2

OpenAPI declaration file content or url

I created an example project at https://github.com/jeroen1602/openapitools-generator-php-issues

Generation Details

I used the following commands for generation:

openapi-generator-cli generate
    -i ./api.yml
    -g php-nextgen
    -c ./generate-nextgen.json
    -o ./out

openapi-generator-cli generate
    -i ./api.yml
    -g php
    -c ./generate-old.json
    -o ./out

Steps to reproduce

Using the example project

• Generate the nextgen version using ./genreate-nextgen.sh (this uses docker to generate the output)
• Look into the NextGen/src/Model/UsedBy.php and search for the getModelName function.
• Generate the old version using ./generate-old.sh (this also uses docker to generate the output)
• Look into the Old/lib/Model/UsedBy.php and search for the getModelName function.
• Use php -l to verify that this is a parse error.

Related issues/PRs

I found this issue but it was closed without anything happening #2544

Suggest a fix

The ModelInterface cannot be changed without making any breaking changes. So that is off the table.

I think that if a getter collision would be generated then it should change the name of the field getter to make sure this doesn't cause a collision.

For example for the model:

Example:
  type: object
  properties:
    model_name:
      type: string
    name:
      type: string

Should create the php model like this:

class Example implements ModelInterface, ArrayAccess, JsonSerializable
{
   // Some boilerplate left out

   /**
    * Implementation for {@link ModelInterface}
    */
   public function getModelName(): string
   {
       return self::$openAPIModelName;
   }

    /**
    * Gets name
    *
    * @return string
    */
   public function getName(): string
   {
       return $this->container['name'];
   }

   /**
    * Gets model_name
    *
    * @return string
    */
   public function getModelNameField(): string // <- renamed the getter by appending `Field` to it.
   {
       return $this->container['model_name'];
   }

}

This does run the risk of creating a new collision if the model_name_field field also exists. But I'm willing to bet that this chance is a lot more rare.

I'm willing to create a PR, but I'm not really sure about the fix for this. Some brainstorming would be appreciated.

Start with the linked example project, its api.yml, and generate-nextgen.sh or generate-old.sh, then inspect NextGen/src/Model/UsedBy.php and Old/lib/Model/UsedBy.php. Run php -l on the generated files and trace the generator entry point responsible for the getters. Done means a model containing model_name no longer declares duplicate getModelName methods and the generated PHP parses successfully.