Sails/Waterline populate does not work in junction table? - node.js

Question

Waterline populate gives me an empty collection when I try to populate a junction table (model) with another junction table (model). I'm using many-to-many through relationship as given here:
https://github.com/balderdashy/waterline/issues/705#issuecomment-60945411
I am using sails-mongo adapter for mongolabs.
The example code,
Model user
/user.js
module.exports = {
schema: true,
attributes: {
id: {
type: 'string',
primaryKey: true,
},
student: {
type: 'string'
},
vendor: {
type: 'string'
},
courses: {
collection: 'vendorcourse',
via: 'users',
through: 'usercourse'
},
coursesProvided: {
collection: 'course',
via: 'vendors',
through: 'vendorcourse'
}
}
};
Model Course
/course.js
module.exports = {
attributes: {
id: {
type: 'string',
primaryKey: true,
autoIncrement: true
},
name: {
type: 'string',
required: true
},
description: {
type: 'string'
},
type: {
type: 'string'
},
vendors: {
collection: 'User',
via: 'courseProvided',
through: 'vendorcourse'
}
}
};
Model vendorcourse
module.exports = {
tableName: 'vendorcourse',
tables: ['user', 'course'],
junctionTable: true,
attributes: {
id: {
type: 'string',
autoIncrement: true,
primaryKey: true
},
name: {
type: 'string',
required: true
},
course: {
columnName: 'course',
type: 'string',
foreignKey: true,
references: 'course',
on: 'id',
via: 'vendors',
groupBy: 'course',
required: true
},
vendor: {
columnName: 'vendor',
type: 'string',
foreignKey: true,
references: 'user',
on: 'id',
via: 'coursesProvided',
groupBy: 'user',
required: true
},
users: {
collection: 'user',
via: 'courses',
through: 'usercourse'
}
}
};
Model usercourse
/usercourse.js
module.exports = {
tableName: 'usercourse',
tables: ['user', 'vendorcourse'],
junctionTable: true,
attributes: {
id: {
type: 'string',
autoIncrement: true,
primaryKey: true
},
course: {
columnName: 'course',
type: 'string',
foreignKey: true,
references: 'vendorcourse',
on: 'id',
via: 'users',
groupBy: 'vendorcourse',
required: true
},
user: {
columnName: 'user',
type: 'string',
foreignKey: true,
references: 'user',
on: 'id',
via: 'courses',
groupBy: 'user',
required: true
}
}
};
When I do
usercourse.find().populate('course').exec(function(error,result){
console.log(result);
});
The output is
[{
'id': //some ID,
'course': [] // this is should be populated with the relative record from the vendorcourse model
'user' : //some ID
}]
The course field should contain the record from the vendorcourse model but instead I get an empty collection [].
The same command works when I do
usercourse.find().populate('user').exec(function(error,result){
console.log(result);
});
The output is as expected
[{
'id': //some ID,
'course': //some ID,
'user': [{ //relevent data }]
}]
Am I doing it wrong? OR Is it that sails/waterline doesnt not support a populate from another junction table