purescript-contrib/purescript-argonaut-core

argonaut Json and Foreign are the same thing?

eskimor opened this issue · 3 comments

eskimor commented

Hi there!

Both Json and Foreign (from purescript-foreign) are simple untyped Javascript data? Is this correct?
If so, it would be nice to make them the same thing in purescript as well, e.g.:

type Json = Foreign

or the other way round. I am currently having the problem that I used the new shiny foreign-generic for serializing my data, but I want to use Affjax which expects a Json and not a Foreign, although they are the same.

I could of course use unsafeCoerce or some other dirty trick, but I really don't like that idea. What if argonaut for some reason changes it's representation some day?

Argonout would then need to depend on purescript-foreign. But is this a problem? It is tiny and this change would further establish purescript-foreign as gateway into the Javascript world, on which also argonaut can build upon.

Alternatively a function foreignToJson would also be ok. Doing unsafeCoerce behind the scenes. I can file a PR for one of those changes - if you want.

Thanks!

eskimor commented

Ok, according to:
purescript-contrib/purescript-affjax#16

they are not the same thing. Don't really understand why though. (I am quite new to Javascript and Web development)

garyb commented

They are very similar, but they have slightly different purposes:

  • Foreign is supposed to be for safely converting from JavaScript values to PureScript. This isn't necessarily just JSON (purescript-dom has many conversions from Foreign), and is also why there is no instance for Either, Tuple, etc. as these types are not "from Javascript".
  • Argonaut is for JSON representations of any arbitrary data.
eskimor commented

Thank you - closing :-)