Crash when serializing result with multiple-nested models without attributes

When sequelize tries to serialize the result of a query returning an instance within an instance (with no attributes), within an instance (with no attributes), it fails with the following error: TypeError: Cannot set property 'C' of undefined

Probably a hidden assumption that there must be at least one attribute included in each included instance somewhere in the code. Notably, with only one nested instance, sequelize manages it, but fails with two or more.

Below is a minimal example showing the problem, one would expect to get the following output in the console, but instead gets the error above.

[{
  B: {
    C: {
      x: "hello"
    }
  }
}]

Code:

/* ----- SETUP ----- */

const Sequelize = require("sequelize")

const db = new Sequelize("mysql://localhost:3306/test")

const A = db.define("A")
const B = db.define("B")
const C = db.define("C", {
  x: Sequelize.STRING
})

A.belongsTo(B)
B.hasOne(C)

db.query("SET FOREIGN_KEY_CHECKS = 0")
  .then(() => db.sync({ force: true }))
  .then(() => A.create())
  .then(a => a.createB())
  .then(() => B.findById(1))
  .then(b => b.createC({ x: "hello" }))

/* ----- PROBLEM STARTS HERE ----- */

  .then(() => A.findAll({ attributes: [], include: [{ attributes: [], model: B, include: [{ model: C, attributes: ["x"] }] }] }))
  .then(x => console.log(x.toJSON()))

Dialect: mysql Database version: 5.7.13 Sequelize version: 3.24.3

[daniel-pedersen]

After some investigating I’ve found that the problem is that groupJoinData in query.js assumes that the rows returned will contain attributes at every level of depth up to the deepest level. This assumption only holds when the depth is 2 or less, because this code in model.js ensures the root attributes array is never empty, instead it tacks on the primaryKeyAttribute, which is filtered out after the result has been passed to groupJoinData.

The problem is that the primaryKeyAttribute is not force added in this way for nested instances, fatally breaking the assumption in groupJoinData. For example in my post the row contains columns ['id','B.C.id','B.C.x'], missing any direct attribute of B. If we add the id attribute for model B in the code above the problem goes away (the returned row contains ['id','B.id','B.C.id','B.C.x']), since the assumption is fulfilled.

Now, there are a few places where one can force the primaryKeyAttribute of nested models with further nested models, such as right after here in query-generator.js, wrapped in an if (include.include && include.attributes.length === 0). This attribute will then simply be filtered when the result returns just as with the root attributes.

[juniorh2o]

Same problem here, I was using version 3.0.0. and query with empty attributes used to work

model: db.User,
    attributes: [],
    required: true,
    include: {
        model: db.Test
    }

After updating to 3.25.0, in order to work I had to add the primary to attributes list, so the objects won’t be undefined:

model: db.User,
    attributes: ['id'],
    required: true,
    include: {
        model: db.Test
    }