Cursor and Collection types are not generic

[danielegarciav]

Under the current type definitions, collections and cursors return documents that are always typed as Object. This means that when using TypeScript, documents must always be type-asserted to a concrete type before being used:

const db = new zango.Db('mydb');
const people = db.collection('people');

const person = people.find({ name: 'John' });
person.name = 'Mike'; // ERROR: Property 'ok' does not exist on type 'Object'.

interface Person {
  name: string;
}

const person2 = people.find({ name: 'John' }) as Person;
person.name = 'Mike'; // OK

This happens because current type definitions are hard-typed to Object and do not allow generics:

zangodb/src/zangodb.d.ts

Lines 21 to 31 in 868babf

	export class Collection {
	name: string;
	aggregate(pipeline: Object[]): Cursor;
	find(expr: Object, projection_spec?: Object): Cursor;
	findOne(expr: Object, projection_spec?: Object,
	cb?: ResultCallback<Object>): Promise<Object>;
	insert(docs: Object|Object[], cb?: Callback): Promise<void>;
	remove(expr: Object, cb?: Callback): Promise<void>;
	update(expr: Object, spec: Object, cb?: Callback): Promise<void>;
	}

We could get inspired by mongodb's type definitions at DefinitelyTyped, and generalize Cursor and Collection, allowing the library consumer to set the document's interface for a given collection, falling back to Record<string, any> if the type parameter is not supplied:

mongodb's Collection type signature - allows a type parameter

mongodb's Collection#findOne type signature - leverages collection type parameter

Using a similar sytem, we could accomplish the following with TypeScript:

interface Person {
  name: string;
}

const db = new zango.Db('mydb');
const people = db.collection<Person>('people');

const person = people.find({ name: 'John' }); // typeof person == Person
person.name = 'Mike'; // OK

I can go ahead and write a quick PR to fix this if you'd like.