Model.create() in MySQL does not return null value when defaultValue hasn't defined

[mytharcher]

Issue Creation Checklist

• I understand that my issue will be automatically closed if I don't fill in the requested information
• I have read the contribution guidelines

Bug Description

In MySQL, if not provide explicit defaultValue: null to the model definition, the created result will not contain the column key.

But in PG it work right (with the null value in result);

Reproducible Example

Here is the link to the SSCCE for this issue:

const db = new Sequelize('mysql://root@localhost/test');

const Book = db.define('Books', {
  title: {
    type: Sequelize.STRING,
    defaultValue: null
  },
  price: {
    type: Sequelize.INTEGER
  }
});

await db.sync({ force: true });

const created = await Book.create();
// in pg here the result will contain `price` key as `null` value
console.log(created.get()); // without `price` key

const found = await Book.findOne();
console.log(found.get()); // with `price` key as `null` value

What do you expect to happen?

{
  id: 1,
  title: null,
  price: null,
  createdAt: 2022-06-22T12:43:13.000Z,
  updatedAt: 2022-06-22T12:43:13.000Z
}

What is actually happening?

{
  title: null,
  id: 1,
  updatedAt: 2022-06-22T12:43:13.333Z,
  createdAt: 2022-06-22T12:43:13.333Z
}

Environment

• Sequelize version: 6.11.0
• Node.js version: v16.15.0
• If TypeScript related: TypeScript version:
• Database & Version: MySQL 8.0.28 & PostgresQL 14.3
• Connector library & Version: mysql2@2.3.3 & pg@8.7.3

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I will need guidance.
• No, I don't have the time, but my company or I are supporting Sequelize through donations on OpenCollective.
• No, I don't have the time, and I understand that I will need to wait until someone from the community or maintainers is interested in resolving my issue.

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[WikiRik]

Do I understand correctly that your expectation is that created.get() equals found.get()?

[ephys]

note for me (or anyone who wants to pick this up) I think this could be easy to fix: In Model.normalizeAttributes, set the defaultValue to null if the attribute allows null and no default value has been specified

[mytharcher]

@WikiRik Exactly! My bad for not describing it so clearly.

What my expectation is created.get() to contain null values which not explicit defined by defaultValue: null. And I only found this in MySQL, so it may be a dialect based bug.

[WikiRik]

No worries, your explanation was fine. Just wanted to double check. As @ephys mentioned it probably is an easy fix. I'll try to check it out over the weekend

[github-actions]

This issue has been automatically marked as stale because it has been open for 14 days without activity. It will be closed if no further activity occurs within the next 14 days. If this is still an issue, just leave a comment or remove the "stale" label. 🙂

[WikiRik]

As can be seen in the linked PR, there are a few things blocking that so this might not get fixed in the short term.