graphql2elm's Introduction

GraphQL to Elm

Generate Elm code based on GraphQL query and schema. Generated code uses jamesmacaulay/elm-graphql library.

See online web generator. Also see Examples.

Status

Feature list consists of:

generate record aliases (type alias) and enums which are used in given query
return type of whole query is being shortened to the first field that consists of more than one subfields
config: known types - so it won't generate new ones but import the existing ones
config: map backend types to front-end types - like Boolean -> Bool between Elixir and Elm
config: decoders for known types
config: support nullable fields by using Maybe

This stuff is available on web generator.

I have no plans for further development since I found another tool with a more interesting approach. It generates code for a whole GraphQL API + generates a decent API for writing queries. It's https://github.com/dillonkearns/elm-graphql - check it out.

Roadmap (deprecated)

field arguments (basics done)
input variables (basics done)
fragments (?)
extend configuration of online web generator for known types

Dev experience

Whole parsing + generation logic is implemented with Kotlin. Because it's nice. And it transpiles to JavaScript.
Parsing of GraphQL queries is done with custom parser. Previously, I started with ANTLR but decided to try and write parser by hand instead of generating it and I'm actually pretty satisfied with it.
Schema is a JSON which comes from a result of GraphQL introspection query (__schema). There's also a parser for it (well, it should be called Interpreter because it's just a JSON).
The web generator is done with Elm 0.19 bootstrapped by code written in Kotlin, later transpiled to JS.