servant VS haskell-awk

> 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.

a HasSwagger instance for NamedRoutes was added in May 2022 (in this commit) but there hasn't been a package release since March

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).

You are highly encouraged to test this release out and let us know what you think ! For bug reports, features requests or any kind of feedback, just open a ticket on our issue tracker.

Even slower than :<|> quadratic compile time in number of routes?

Check this out https://github.com/haskell-servant/servant/issues/335#issuecomment-172300487

I use a smooth awk-like tool called hawk for similar reasons and it sure is nice, can recommend.

Looking for a few projects that make use of it, I found accelerate, hawk, polysemy and pretty-simple, so I'll be interested to poke around in their code and see how they have things set up.

For easy, rapid development. If I'm processing text at the command-line and I realize that I need a Unix command-line tool which doesn't yet exist, say, one which reverses each line, I can very easily pipe my text into ghc -e 'interact (unlines . reverse . lines)' (or even more easily as hawk -md L.reverse) and move on to the next step of my text manipulation. If I had to open a text editor, create a new Haskell project, write the code which grabs the input, processes the lines, and then outputs the result, then this amount of friction is large enough that it's not worth it for a one time task. I'd probably find a different way to do it which is less expedient than the interact solution but more expedient than creating a new Haskell project.

hint maintainer here! To use dependencies, you need to use unsafeRunInterpreterWithArgs to pass extra -package-db arguments to ghc. In my hawk project, I'm trying hard to use the same package database in which hawk itself was installed, so I wrote a bunch of code to detect which installation method was used and to figure out the package database folder from there.