Fix id duplication

[abhiarya-uvic]

We are students from University of Victoria working on architectural review of Strapi system as part of our course project. We found that the id and _id are duplicated in the JSON response from the API. We also analysed previous issues mentioned and we know that Strapi is handling two ORM right now (Mongoose and Bookshelf) and that's why it is duplicated.

However, it is unnecessary to return redundant value of ids (id and _id) with every API request made. So, we are proposing changes to Strapi-generate-api package to bandaid this issue.

[Aurelsicoko]

@abhiarya-uvic Thank you (or all of you) for this PR! You're right it's unnecessary to return identicals values in the same object. In this case, I think we need to handle the issue deeper.

• First of all, the issue is mainly caused by MongoDB. The _id attribute is specific to MongoDB and most of the others databases (SQL) are using the id attribute as a unique identifier. To me, it makes more sense to use the id attribute everywhere to keep our codebase consistent.

• So, I would focus my effort on MongoDB which means in our connector strapi-mongoose. And I would try to hide the _id attribute and replace it with the id attribute.

• I also need to make sure the id attribute is never saved. Currently, it's only the case when you're using the Content Manager (administration panel). If you're using the API to create the entries, the issue doesn't appear.

---

Here my proposal

collection.schema.pre('save', function (next) {
  // Delete the id and avoid to save it.
  delete this.id;
  
  next();
});

collection.schema.options.toObject = collection.schema.options.toJSON = {
  virtuals: true,
  transform: function (doc, returned, opts) {
    returned.id = returned._id;

    delete returned._id;
  }
};

This solution virtualises the id attribute. It removes it from the database and it always displays the id attribute instead of _id if you're not fetching data with the lean method.

[abhiarya-uvic]

@Aurelsicoko We had a discussion among our team members and we think that the solution you proposed seems better to rectify this issue. Hiding the _id attribute and replacing it with the id attribute looks good. Thanks so much!

[Aurelsicoko]

@abhiarya-uvic Awesome, we're waiting for the changes in this file (https://github.com/strapi/strapi/blob/master/packages/strapi-mongoose/lib/index.js). Feel free to ask us anything if you need help!