Sequelize findOne returned instance. Row is in dataValues, but direct properties on instance are undefined

Question

Context: I'm testing a simple model into and out of the database. Not a real test, it's a precursor to some integration tests. Using Sequelize and findOne.

The problem: The direct data on the returned model instance, i.e. email.ulid, email.address, email.isVerified are undefined.

My question: Why are they undefined?

Sequelize: 5.15.0
Typescript: 3.5.3
mysql  Ver 15.1 Distrib 10.4.6-MariaDB

Record into database:

await testingDatabase.sync({
  force: true
}).then(async () => {
  await Email.create({
    ulid: the_ulid.bytes,
    address: "[email protected]",
    isVerified: false
  })
})

Fetch the record back:

await Email.findOne({
  where: { 
    address: "[email protected]"
  }
  , rejectOnEmpty: true //to shut typescript up
}).then( emailData => {
   console.log("Email: ", email)
})

Console.log of email instance:

    Email:  Email {                                                                                                                                                      
      dataValues: {                                                                                                                                                      
        ulid: <Buffer 01 6c a3 36 11 9c 1e 9b a6 ce 60 b7 33 3e e7 21>,                                                                                                  
        address: '[email protected]',                                                                                                                                    
        isVerified: false,                                                                                                                                               
        deletedAt: null,                                                                                                                                                 
        createdAt: 2019-08-18T05:32:05.000Z,                                                                                                                             
        updatedAt: 2019-08-18T05:32:05.000Z                                                                                                                              
      },                                                                                                                                                                 
      ...,
      isNewRecord: false,
      ulid: undefined,
      address: undefined,
      isVerified: undefined,
      createdAt: undefined,
      updatedAt: undefined,
      deletedAt: undefined
    }

^^^ As is clear, immediately above, all of the direct attributes on the instance are null.

The following works, but with the side-effect that isVerified is returned as a 0 rather than false and subsequently fails a direct comparison with the original data. Additionally, I lose other functionality of the model instance that will come in handy on more complex models:

Email.findOne({
  where: { address: "[email protected]" }
, raw: true 
, rejectOnEmpty: true
})

These also work, but with the consequence that Typescript complains about the returned object not having the properties I then access (although they do exist and the test works):

.then( emailData => {
  console.log("All getters: ", emailData.get())
  // AND
  console.log("All getters(plain): ", emailData.get({plain: true}))
  // AND
  console.log("toJSON: ", emailData.toJSON())
})

This next one (suggested by Vivek), works insofar as the data is available, but JSON.parse fails to handle the Buffer properly:

const dataOnly = JSON.parse(JSON.stringify(emailData))

Others have complained (SE answer) that console.log somehow misprints the instance, yet every other way I access these properties they are still undefined.

Answer 1

I hit the same issue but in a slightly different context.

My solution was not to use the ESNext target in my tsconfig.json. Using ES2021 or any other target solved the problem.

Answer 2

Solution:

The problem was with a Babel plugin.

Setting up Sequelize models as per the Sequelize/Typescript documentation, defines class properties on each model representing model fields.

The babel plugin:

"@babel/proposal-class-properties"

within:

plugins: [
  "@babel/proposal-class-properties"
, ...
]

Transforms these class properties into defineProperty() calls on the model Class object, called in turn by the helper _defineProperty():

  _defineProperty(this, "yourFieldName", void 0);

This initializes the property on the object with the value undefined.

Evidently, when findOne subsequently tried to update the model, it refused to overwrite these existing properties on the model.