Associations in sequelize not working as intended

Question

I am attempting to output a nested relation where

Cat.hasMany(legs)

Leg.belongsTo(cat)

Leg.hasOne(paw)

paw.hasMany(leg)

Here is my Cat Model:

module.exports = (sequelize, DataTypes) => {
  const Cat = sequelize.define('Cat', {
    userId: {
      type: DataTypes.STRING,
    },
  }, {});

  Cat.associate = function (models) {
    Cat.hasMany(models.Leg, {
      foreignKey: 'catId',
      as: 'legs',
    });
  };
  return Cat;
};

My Legs Model:

module.exports = (sequelize, DataTypes) => {
  const Leg = sequelize.define('Leg', {
    originalValue: DataTypes.JSON,
    newValue: DataTypes.JSON,
    legId: DataTypes.INTEGER,
    objectId: DataTypes.INTEGER,
    pawId: DataTypes.INTEGER,
  }, {});

  Leg.associate = function (models) {
    Leg.belongsTo(models.Cat, {
      foreignKey: 'LegId',
      onDelete: 'CASCADE',
    });
    Leg.hasOne(models.Paw, {
      foreignKey: 'pawId',
    });
  };
  return Leg;
};

Here is my Paw model

module.exports = (sequelize, DataTypes) => {
  const Paw = sequelize.define('Paw', {
    pawType: DataTypes.STRING,
  }, {});
  Paw.associate = function (models) {
    Paw.hasMany(models.Leg, {
      foreignKey: 'pawId',
      as: 'paws',
    });
  };
  return Paw;
};

Currently My code is outputting this when i query the Cat Table

[
    {
        "id": 1,
        "userId": "2wdfs",
        "createdAt": "2018-04-14T20:12:47.112Z",
        "updatedAt": "2018-04-14T20:12:47.112Z",
        "legs": [
            {
                "id": 1,
                "catId": 1,
                "pawId": 1,
                "createdAt": "2018-04-14T20:12:54.500Z",
                "updatedAt": "2018-04-14T20:12:54.500Z"
            }
        ]
    }
]

However I would like the pawType from the paws table to also be present when listing everything from the cat table. Something more along the lines of this:

[
    {
        "id": 1,
        "userId": "2wdfs",
        "createdAt": "2018-04-14T20:12:47.112Z",
        "updatedAt": "2018-04-14T20:12:47.112Z",
        "legs": [
            {
                "id": 1,
                "catId": 1,
                "paws" : [
                   {
                    "id": 1,
                    "pawType": "cute"
                   }
                ]
                "createdAt": "2018-04-14T20:12:54.500Z",
                "updatedAt": "2018-04-14T20:12:54.500Z"
            }
        ]
    }
]

Additionally, Here is the query I am using to retrieve the Cats.

return Cat.findAll({ include: [{ model: Leg, as: 'legs',include [{model: Paw,}], }], })

This is the error that is returning,

{ SequelizeDatabaseError: column legs->Paw.pawId does not exist
{ error: column legs->Paw.pawId does not exist

And the full SQL command

   sql: 'SELECT "Cat"."id", "Cat"."userId", "Cat"."createdAt", "Cat"."updatedAt", "legs"."id" AS "legs.id", "legs"."originalValue" AS "legs.originalValue", "legs"."newValue" AS "legs.newValue", "legs"."catId" AS "legs.catId", "legs"."objectId" AS "legs.objectId", "legs"."pawId" AS "legs.pawId", "legs"."createdAt" AS "legs.createdAt", "legs"."updatedAt" AS "legs.updatedAt", "legs->Paw"."id" AS "legs.Paw.id", "legs->Paw"."paw" AS "legs.Paw.paw", "legs->Paw"."pawId" AS "legs.Paw.pawId", "legs->Paw"."createdAt" AS "legs.Paw.createdAt", "legs->Paw"."updatedAt" AS "legs.Paw.updatedAt" FROM "Cats" AS "Cat" LEFT OUTER JOIN "Legs" AS "legs" ON "Cat"."id" = "legs"."catId" LEFT OUTER JOIN "Paws" AS "legs->Paw" ON "legs"."id" = "legs->Paw"."pawId";' },

Answer 1

There are many issues. I'll try to address them incrementally.

1) Models By default, if you do not declare a primaryKey, then sequelize automatically adds an id column for you. Thus legId isn't a useful column.

Furthermore, if you associate a model, the foreignKey reference is added for you, thus pawId shouldn't be declared.

Thus Legs.js should be modified to:

module.exports = (sequelize, DataTypes) => {
  var Leg = sequelize.define('Leg', {
    originalValue: DataTypes.JSON,
    newValue: DataTypes.JSON,
    objectId: DataTypes.INTEGER // not entirely sure what this is 
  })
  Leg.associate = function (models) {
    // associations
  }
  return Leg
}

The above gives me the following columns in pgAdmin:

2) Associations

The following association doesn't make sense, and should cause an error:

Leg.hasOne(Paw)
Paw.hasMany(Leg)

Unhandled rejection Error: Cyclic dependency found. Legs is dependent of itself.
Dependency chain: Legs -> Paws => Legs

Each Leg should have one Paw, and thus I suggest the following:

Leg.associate = function (models) {
  // Leg.belongsTo(models.Cat)
  Leg.hasOne(models.Paw, {
    foreignKey: 'pawId',
    as: 'paw'
  })
}

Paw.associate = function (models) {
  Paw.belongsTo(models.Leg, {
    as: 'leg' // note this changed to make more sense
    foreignKey: 'pawId'
  })
}

3) Foreign Keys

Leg.belongsTo(models.Cat, {
  foreignKey: 'catId', // this should match
  onDelete: 'CASCADE'
})

Cat.hasMany(models.Leg, {
  foreignKey: 'catId', // this should match
  as: 'legs'
})

4) Eager Loading

When eager loading nested associations, you have to include them. You should also use as alias that matches your model associations:

Cat.findAll({
  include: [{
    model: Leg,
    as: 'legs', // Cat.legs 
    include: [{
      model: Paw,
      as: 'paw' // Leg.paw instead of Leg.pawId
    }]
  }]
})

Using this entire setup and the above query, I obtain:

[
  {
    "id": 1,
    "userId": "1",
    "createdAt": "2018-04-15T11:22:59.888Z",
    "updatedAt": "2018-04-15T11:22:59.888Z",
    "legs": [
      {
        "id": 1,
        "originalValue": null,
        "newValue": null,
        "objectId": null,
        "createdAt": "2018-04-15T11:22:59.901Z",
        "updatedAt": "2018-04-15T11:22:59.901Z",
        "catId": 1,
        "paw": {
          "id": 1,
          "pawType": null,
          "createdAt": "2018-04-15T11:22:59.906Z",
          "updatedAt": "2018-04-15T11:22:59.906Z",
          "pawId": 1
        }
      }
    ]
  }
]

Extra

Because this is obviously a practice setup, you could modify Paw to be a belongsToMany relation (perhaps you have conjoined cats by the paw?) as follows:

Paw.associate = function (models) {
  Paw.belongsToMany(models.Leg, {
    foreignKey: 'pawId',
    through: 'PawLegs  // a through join table MUST be defined
  })
}

This would be the correct way to implement what you initially tried to with

Leg.hasOne(paw)
paw.hasMany(leg)