Google-api-nodejs-client: Add simultaneous promise and callback support

[jmdobry]

[GitTom]

+1

For example, see how they added promise support to AWS node library:
https://blogs.aws.amazon.com/javascript/post/Tx3BZ2DC4XARUGG/Support-for-Promises-in-the-SDK

[lirbank]

See also MongoDBs node driver. It very nicely supports both callbacks and promises in the same driver.
http://mongodb.github.io/node-mongodb-native/2.2/api/

[thepatrick]

It's incredibly confusing that the "JavaScript client library" supports promises but this library doesn't.

How can progress be made on this? We have async/await now, and those work brilliantly with libraries with promise support.

[BerndErnst]

Seems like Google doesn't love NodeJs/Javascript 💔💔💔

[simonh1000]

Googles Docs recommend using promises but I cannot find how to use them with this library

[Mozcatel]

+1
Seems we cant use the full asynchronous control Node allows us on this library, either Promises or async/await

[machineghost]

So this ticket is nearly two years old and hasn't had any dev response in that entire time ... does that mean it's dead?

If not, Node's util.promisify seems like it would make solving this issue trivial. It "takes a function following the common error-first callback style, i.e. taking a (err, value) => ... callback as the last argument, and returns a version that returns promises." ... and all of the API calls I've seen in this library follow that format (ie. callback is the last arg and the callback expects an error as the first arg and result as the second).

I would be happy to submit a PR that simply calls util.promisify on every callback-using function in this library (and updates the consumers appropriately as well of course).

[JustinBeckwith]

Nope, just slow moving :) This project is largely maintained by volunteers on free time, so sometimes stuff like this can take a while. We still very much want to do it, but a few things need to happen first.

In the meantime - you can use tools like pify today to promisify the API pretty easily.

We also love PRs :)

[machineghost]

We also love PRs :)

As I said (in an edit, so you might have missed it) I'd be happy to submit one, but only if it will actually be used. I certainly wouldn't want to go through and promisify everything if the library's maintainers don't want that.

[JustinBeckwith]

Apologies! I did miss the edit. I don't think we want to run through and util.promisfy everything. We're using TypeScript, which lets us write our code with promises or Async/Await, and then transpile down to es5 so we can support node 4 and 6. I believe util.promisfy is only in Node 8, so that's sadly off the table. That's where (if we need to, which we shouldn't) we could use pify.

We already went through the painful process in #891 of swapping out from request to axios in the underlying auth library, so that means the table is actually set for supporting both callbacks and promises. To support back-compat, I really think we need to do both. Here's an example of how we do it in the auth library:
https://github.com/google/google-auth-library-nodejs/blob/master/src/auth/oauth2client.ts#L464

The work here is to introduce a similar pattern. We need function overloads for public methods that support both the callback and promise based workflows. Famous last words... but I think we've already done most of the heavy lifting here :)

I would be ecstatic to review a PR that takes this approach!

[machineghost]

We're using TypeScript

Ugh. My apologies but I'm afraid I have to rescind my offer of a PR, as I'm really not a fan of TypeScript.

I do hope someone else will pick up the task though, as I would :heart: being able to use this library with async/await.

[acoll]

Would something as simple as this work? Basically return the called request functions (which already have conditional promise support) and remove the call to normalize the callback function.

https://github.com/acoll/google-api-nodejs-client/commit/998e1f6d1f7315692a776efccd970e1290f046a5

I was just playing around with this quickly on my local but it seemed to work for the couple of apis I'm using. I can send a PR with some tests if this seems like the right direction.

[naturalethic]

@acoll Thanks a lot for that I adapted it for my own use.

[naturalethic]

Well that was a lot of work. Nice job.

[qraynaud]

There is an issue with how this was implemented.

Before the APIs returned a stream and now they don't. Which means some examples on the online document are broken (like here, first Node exemple).

What is more, in this use case, we want to download a file. It might weight Gbs or even Tbs. Using a promise that waits until the request completes (or a callback for that matter) means it will load the whole file in RAM. This is totally unacceptable right?! I want to pipe the request in something and be rid of it!

It would be great to return a proxy instead of the actual axios promise. It could accept to act like a stream or like a promise depending on how it's used!

[qraynaud]

The other solution would be to expose the responseType attribute of axios. So I could set it to stream and it would be perfect too!

[qraynaud]

Ok, reading the code I found out it is indeed exposed as the second parameter...