Use microlens instead of lens

[leptonyu]

Lens is very heavy library, many libraries use microlens instead. Can you replace it?

[phadej]

I'm sorry, but the answer is no.

We (me and @alpmestan) agreed thatlens dependencies can be added to servant-* packages.
lens is virtually unavoidable in any non-trivial real worldservant applications, something in your dependencies transitively depends on it (even you don't use lens yourself) or you have to be extra careful when picking them.
E.g. servant-client depends on kan-extensions since recently.

Also it's swagger2 which pulls in lens and it defines Prisms in https://hackage.haskell.org/package/swagger2-2.4/docs/Data-Swagger-Lens.html, so profunctors would be needed with microlens ecosystem too.

There aren't many packages between profunctors and lens. Even less between kan-extensions and lens.

cabal, stack and nix are all good quite good at caching dependencies, and the acme-kmett is quite stable (new releases happen rarely).

[leptonyu]

Thanks.

It seems acme-kmett's README.md needs a little modification.

GHC-8.6.4 -> GHC-8.6.5

[alpmestan]

Right, I think it's a bit tricky for us to change this. But if I'm not mistaken, none of servant, servant-client[-core] nor servant-server depend on lens (transitively), do they? Only the -docs/-swagger/... packages do, IIRC. If we had an easy path towards becoming lens lib agnostic or another solution that would let us not depend on lens, we'd take it but I don't think that's the case, as explained by @phadej. If that changes, we can revisit this request. :-)

[neongreen]

microlens itself is lens-lib-agnostic. As in, you don't lose anything by using microlens instead of lens — van Laarhoven lenses are compatible with each other.

If you are exporting prisms, though, you're better off with lens.

[akhesaCaro]

Hi,
Servant-swagger will be moved into the main Servant repo (see : haskell-servant/servant#1475)
If this issue is still relevant, would it be possible for you to summit it there? : https://github.com/haskell-servant/servant/issues

Thanks in advance!