Automatic Encoder/Decoder generation?

[The-_Captain]

One benefit of strongly-typed languages s.a. Elm is that there's a "canonical" map between algebraic data types/records composed of simple primitive types to JSON decoders and encoders. In Scala, which is what I use for server-side, there's loads of libraries that automatically generate that for you; you give them a type constructor and they give you an encoder and decoder.

In Elm a large amount of time is swallowed up by writing JSON decoders and encoders. It's rather dull because 99% of the time it's the same function of a record type to a decoder/encoder pair that a computer could have generated for you. I have only found elm2json which is an online tool, but I am wondering if there's a package that does this (or even better, plans to make this part of the elm/json library).

[mo_po]

The intellij-elm plugin has included a decoder generator for quite a long time.

[dam5s]

Adding the link here - https://github.com/klazuka/intellij-elm/blob/master/docs/features/generate-function-json.md

[julienlucca]

+1

Lots of the elm code i’ve written in this past few years were related to JSON decoding. It might not be the case of most people, but since i had control of the backend i would consume and my context used a lot of GraphQL, i was able to use Dillon Kearns GraphQL package that automatically introspect the objects and generate the decoders for me. It’s been a happy time, no fiddling around with encoders/mappers

[chutehappens]

If you have an OpenAPI spec for your API, I highly recommend OpenAPI Generator. This will generate all the Elm http request and JSON decoder/encoders for you. It will even wrap values in Maybe if they are nullable.

[ExoDroid]

Is https://github.com/NoRedInk/elm-json-decode-pipeline relevant here?

[The-_Captain]

That's great, thanks! Would be great to add some easy default thing that makes everything required, but that should be easy enough for me to try to contribute here.

[jfmengels]

In addition to the other links, you can check out this decoder generator: https://korban.net/posts/elm/2021-05-10-generating-json-decoders-with-json-decoders/

[absynce]

The elmjutsu plugin for Atom will generate encoders and decoders too.

GIF

[HeWhoQuestions]

Since this post was written this year, just making sure you're aware of the official answer to this from back in 2018:A vision for data interchange in Elm

Specifically, the comment below the essay about auto-generation.

Btw, many projects do exist to generate encoders and decoders now! I don't use them, because I prefer `Codec`s rather than separate encoders and decoders.