undefined attributes following typescript example

Issue Description

What are you doing?

// this is a copy of https://sequelize.org/master/manual/typescript.html
import { Sequelize, Model, DataTypes, BuildOptions } from 'sequelize';
import { HasManyGetAssociationsMixin, HasManyAddAssociationMixin, HasManyHasAssociationMixin, Association, HasManyCountAssociationsMixin, HasManyCreateAssociationMixin } from 'sequelize';

class User extends Model {
  public id!: number; // Note that the `null assertion` `!` is required in strict mode.
  public name!: string;
  public preferredName!: string | null; // for nullable fields

  // timestamps!
  public readonly createdAt!: Date;
  public readonly updatedAt!: Date;

  // Since TS cannot determine model association at compile time
  // we have to declare them here purely virtually
  // these will not exist until `Model.init` was called.

  public getProjects!: HasManyGetAssociationsMixin<Project>; // Note the null assertions!
  public addProject!: HasManyAddAssociationMixin<Project, number>;
  public hasProject!: HasManyHasAssociationMixin<Project, number>;
  public countProjects!: HasManyCountAssociationsMixin;
  public createProject!: HasManyCreateAssociationMixin<Project>;

  // You can also pre-declare possible inclusions, these will only be populated if you
  // actively include a relation.
  public readonly projects?: Project[]; // Note this is optional since it's only populated when explicitly requested in code

  public static associations: {
    projects: Association<User, Project>;
  };
}

const sequelize = new Sequelize('mysql://root:asd123@localhost:3306/mydb');

class Project extends Model {
  public id!: number;
  public ownerId!: number;
  public name!: string;

  public readonly createdAt!: Date;
  public readonly updatedAt!: Date;
}

class Address extends Model {
  public userId!: number;
  public address!: string;

  public readonly createdAt!: Date;
  public readonly updatedAt!: Date;
}

Project.init({
  id: {
    type: DataTypes.INTEGER.UNSIGNED, // you can omit the `new` but this is discouraged
    autoIncrement: true,
    primaryKey: true,
  },
  ownerId: {
    type: DataTypes.INTEGER.UNSIGNED,
    allowNull: false,
  },
  name: {
    type: new DataTypes.STRING(128),
    allowNull: false,
  }
}, {
  sequelize,
  tableName: 'projects',
});

User.init({
  id: {
    type: DataTypes.INTEGER.UNSIGNED,
    autoIncrement: true,
    primaryKey: true,
  },
  name: {
    type: new DataTypes.STRING(128),
    allowNull: false,
  },
  preferredName: {
    type: new DataTypes.STRING(128),
    allowNull: true
  }
}, {
  tableName: 'users',
  sequelize: sequelize, // this bit is important
});

Address.init({
  userId: {
    type: DataTypes.INTEGER.UNSIGNED,
  },
  address: {
    type: new DataTypes.STRING(128),
    allowNull: false,
  }
}, {
  tableName: 'address',
  sequelize: sequelize, // this bit is important
});

// Here we associate which actually populates out pre-declared `association` static and other methods.
User.hasMany(Project, {
  sourceKey: 'id',
  foreignKey: 'ownerId',
  as: 'projects' // this determines the name in `associations`!
});

Address.belongsTo(User, {targetKey: 'id'});
User.hasOne(Address,{sourceKey: 'id'});

async function stuff() {
  // Please note that when using async/await you lose the `bluebird` promise context
  // and you fall back to native
  const newUser = await User.create({
    name: 'Johnny',
    preferredName: 'John',
  });
  console.log(newUser.id, newUser.name, newUser.preferredName);

  const project = await newUser.createProject({
    name: 'first!',
  });

  const ourUser = await User.findByPk(1, {
    include: [User.associations.projects],
    rejectOnEmpty: true, // Specifying true here removes `null` from the return type!
  });
  console.log(ourUser.projects![0].name); // Note the `!` null assertion since TS can't know if we included
                                          // the model or not
}

My tsconfig:

"compilerOptions": {
    "outDir": "dist",
    "sourceMap": false,
    "allowJs": true,
    "noUnusedLocals": true,
    "noUnusedParameters": false,
    "resolveJsonModule": true,
    "module": "commonjs",
    "strictNullChecks": true,
    "allowSyntheticDefaultImports": true,
    "lib": ["es7", "es2015", "dom"],
    "target": "es2015",
    "baseUrl": "."
  }

What do you expect to happen?

I expect ourUser.projects to be defined

What is actually happening?

console.log(ourUser.projects) // undefined

Context

Note that I also observe some strange behavior: when I add the flag raw: true in the query, the result looks like this:

{ 
  id: 1,
  createdAt: 2019-11-06T08:35:49.172Z,
  updatedAt: 2019-11-06T08:35:49.172Z,
  'projects.id': 1,
  'projects.ownerId': 1,
  'projects.createdAt': 2019-11-08T12:41:40.520Z,
  'projects.updatedAt': 2019-11-08T15:32:42.822Z
}

Environment

• Sequelize version: 5.21.2
• Node.js version: v10.16.3
• Operating System: OSX
• TypeScript version: 3.6.3

Issue Template Checklist

How does this problem relate to dialects?

• I think this problem happens regardless of the dialect.
• I think this problem happens only for the following dialect(s):
• I don’t know, I was using PUT-YOUR-DIALECT-HERE, with connector library version XXX and database version XXX

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 don’t know how to start, I would need guidance.
• No, I don’t have the time, although I believe I could do it if I had the time…
• No, I don’t have the time and I wouldn’t even know how to start.

[nicgirault]

For French readers: this post helped me understand what is happening: https://openclassrooms.com/forum/sujet/proprietes-de-classe-avec-node-12-babel. It seems there is a conflict with babel class properties. Migrating to node v12 and removing babel plugin @babel/proposal-class-properties solved my issue

[ephys]

Merged https://github.com/sequelize/sequelize/pull/13877