Make a library with datatypes compatible between GHC and GHCJS

[mb21]

1. Make conditionals in .cabal file, e.g.:

   library
     if impl(ghcjs)
       build-depends:
         ghcjs-base >= 0.2.0.0
     else
       build-depends:
         aeson >= 1.x.x.x

2. Use CPP to select proper imports in each implementation, e.g.:

   {-# LANGUAGE CPP #-}
   
   #ifdef ghcjs_HOST_OS
   import JavaScript.JSON.Types.Internal
   import JavaScript.JSON.Types.Instances
   import JavaScript.JSON.Types.Generic ()
   #else
   import Data.Aeson
   #endif

3. Use DeriveGeneric extension to automate generation of from/to json:

   {-# LANGUAGE DeriveGeneric #-}
   ...
   import GHC.Generics
   ...
   data AAA = AAA
     { fieldAAAN1       :: !Int
     , fieldBBBJStringT :: !JSString
     , anotherThingy    :: !Double
     } deriving Generic
   
   instance ToJSON AAA
   instance FromJSON AAA

4. Hope for good luck!

[achirkin]

Good! Let's make it into a small cross-platform library libs/hs/qua-web-api. Also try to keep a bare minimum of dependencies - this is important for qua-view (atm, qua-view.js can be up to 15 mb without optimizations already).

Another, connected task is to track all necessary api calls. What we remember so far:

• user review form
• expert review form
• list of review (user and expert)
• get scenario from link (though scenario itself does not need a description in qua-web-api, because it is just a bytestring from the point of view of qua-kit)
• get session properties (qua-view settings)

[NorfairKing]

Because you're using ghcjs and reflex, you could use servant and reflex-servant to take care of most of the boiler plate.

[achirkin]

Yes, we could. Though, it is debatable if the benefit of using servant API outweights the costs of integrating servant into yesod, porting existing yesod handlers, and, most importantly, having more deps in GHCJS output. Do you know how much servant-reflex adds up to the output size? If around 100KB then I would agree, if couple megabytes then it would be too much.

[mb21]

This has been done on the reflex branch...