Consider using Promise#nodeify in JS drivers

[dminkovsky]

From IRC:

01:08 < phuh> neumino: Did you know bluebird has .nodeify() that helps simply code like this one?
https://github.com/rethinkdb/rethinkdb/blob/next/drivers/javascript/ast.coffee#L99-L126
01:09 < phuh> documentation says "There is no effect on peformance if the user doesn't actually pass a node-style callback function."

I've also been thinking about this for a while. I believe nodeify() would simply things in that span, and similar spans of the JS driver. nodeify() is cool and also provides an easy way to support the callback interface while using Promise.using() for a possible connection pool implementation (#281 (comment)).

[coffeemug]

/cc @neumino. What do you think?

[neumino]

I actually used nodeify in rethinkdbdash for 1.14, and was planning to do the same with the official driver.

[thelinuxlich]

+1

[neumino]

Part of this issue will be to bump blubird to 2.x

[dminkovsky]

Totally did not notice we weren't on 2.x :)

[neumino]

In branch michel_2973_nodeify
Review 2149 assigned to @AtnNn and @Tryneus

The bluebird dependency is bumped to 2.3.2

[pilwon]

@neumino Also consider dropping the use of new Promise.

From Bluebird API doc:

Note: In Node.JS it is **very unlikely* that you will ever need to create promises yourself, see promisification*

Also refer to the deferred anti-pattern.

Suggestions:

• .promisify()
• Promise.method()
• return Promise.resolve()
• return Promise.reject()
• re-throw error in .catch()

[neumino]

The idea behind Promise.promisifyAll is to get promises from libraries with asynchronous function (like fs), and then just using these promises.
The thing is that doesn't work for the net module.

For example, you could call promisify on socket.write but it will be resolved when the data is written out, not when you receive a response from the server (you actually have to parse the data sent form the server to know what query it matches first).

[pilwon]

@neumino I understand the use of new Promise is necessary for some cases (ex: cursor.coffee). However, couldn't we simplify this code with Promise.method or Promise.reject?

[neumino]

Oh, thanks @pilwon -- I didn't pay attention to the big try/catch there. I removed the try and just call Promise.reject.
Updated in branch michel_2973_nodeify.

I'm not a big fan of wrapping a method of a CoffeeScript class with Promise.method. I haven't tried it, but I wouldn't be surprised if it was to lead to tricky behaviors like this one #1948 (comment).

[neumino]

Merged in next as dbae9bd
Ship 1.16