servant VS coffeescript

> do you really have to understand language extensions?

You do when your code doesn't compile and you're trying to figure out what the error message means, or when the library you want to use makes heavy use of it for even basic functionality.

> These days one just enables GHC2021

My experience was pre-GHC2021. I basically had to enable at a minimum 5-6 language extensions in every single file.

> Mostly they're just about removing unnecessary restrictions from the older standard.

Yeah, those ones are usually fine. I have zero objection to things like FlexibleInstances or DeriveFoldable.

> Could you give an example?

I believe I was trying to implement Central Authentication Service using Servant. However, that required returning a custom HTTP status code. There has been an open Github issue for this since 2017, but it seems to require basically rewriting the entire framework: https://github.com/haskell-servant/servant/issues/732

Looking back at it now Servant does have "ServerError", but that basically requires giving up all the advantages Servant claims to have and I believe it was not a viable option at the time. Looking at the timeline I was probably also on Servant 0.15, and there seems to have been a rewrite since then.

I vaguely recall running into a similar issue trying to interact with a database, but I can't remember the details of that.

If you don't like this style, the usual alternative is to change mkDualAuthHandler to take two additional arguments, Proxy tag0 and Proxy tag1 (as e.g. lots of Servant functions do, for historical reasons).

Dunno if this is helpful, but I found this github issue about ResourceT and servant https://github.com/haskell-servant/servant/issues/1345

And what about the cabal repl --with-compiler=doctest, which was added recently, in doctest v0.20? I recently submitted a PR for Servant to use this in place of GHC environment files, because it seems less finicky to me. Was this a bad idea?

I asked a somewhat relevant question recently. Maybe you'll find this discussion somewhat helpful: https://github.com/haskell-servant/servant/issues/1547; two packages were talked about. One of the folks from Well Typed replied, and said they tried it recently (and worked fine).

Hey, is it possible this could solve the quadratic compile times issue for Servant routes? I was under the impression the slowdown was related to GHC being slow processing giant types, so maybe breaking the API down into records is just the thing...

You'll actually have to use the unreleased servant-auth-server from master (see here for details). I need to push a release :-)

We use servant library that allows us to describe API at the type level and check during the compilation whether both the server handlers and the client functions use correct parameters of the required types and correspond to the current API version (if you forgot to change the client function at the frontend, it just won’t be built).

Since nobody has mentioned it yet, there is an outstanding issue about quadratic compile times in Servant.

That said, there are ways to embrace the JS ecosystem without actually using JavaScript. Many popular languages have transpilers that will convert code written in that particular language into something that will run natively in a web browser (in other words, JavaScript). Even TypeScript is a language that gets transpiled into JavaScript, so it's not that outrageous of a concept, it just gets more difficult to do the further you get away from languages that don't already look like JavaScript.

As a front-end web developer, do you still use CoffeeScript or jQuery? Unlikely, as TypeScript, ES/TC39 and Babel (and the retirement of Internet Explorer thanks to @codepo8 and his EDGE team) have helped to transform JavaScript into some kind of a modern programming language.

CoffeeScript

On the other hand, companies choose React because that's where all the developers are. If you want to build something that can be maintained years from now, you better not choose the next hype train that goes straight to nowhere (remember CoffeeScript ?). You want something battle tested that has stood the test of time, where you won't have trouble finding developers to scale once you need to. And nobody ever got fired for choosing React.

http://coffeescript.org/#expressions

this comes from Lisp and makes a lot of things easier. Obviously this was not implemented in ES6 because it would break compatibility and there is also some problems with implicit returns that made the feature a bit weird

I wonder if a syntax like this for JS would work:

const eldest = if (24>41) { escape "Liz" } else { escape "Ike" }

with "escape" working like a mix of "break" and "return". But even then this is likely to cause incompatibilities

Coffeescript[1] was a flavour of JS syntax meant to look similar to Ruby syntax. You just compiled it back to JS. It was nice for working on Rails projects since it made everything feel more “cohesive”.

I assume this project is here for older Coffeescript[1] projects who want to start using typescript, and need access to interfaces/types that were present in old CS files.

[1] https://coffeescript.org/