Convert arbitrary scalars to AST.

[anhldbk]

Hi guys,

I'm trying to make a configuration language based on GraphQL (so I don't have write lexer/parser on my own). I want to support JSON as an input type by using graphql-type-json. But I've got an issue of parsing AST as described by this issue taion/graphql-type-json#73.

@taion tell me that

That utility function (astFromValue) doesn't support converting arbitrary scalars to AST

I've found a hack to overcome the issue. Should I make a PR against this one?

[IvanGoncharov]

@anhldbk That's why we implemented valueFromASTUntyped

graphql-js/src/utilities/valueFromASTUntyped.js

Lines 18 to 36 in 8aef229

	* Produces a JavaScript value given a GraphQL Value AST.
	*
	* Unlike `valueFromAST()`, no type is provided. The resulting JavaScript value
	* will reflect the provided GraphQL value AST.
	*
	* | GraphQL Value | JavaScript Value |
	* | -------------------- | ---------------- |
	* | Input Object | Object |
	* | List | Array |
	* | Boolean | Boolean |
	* | String / Enum | String |
	* | Int / Float | Number |
	* | Null | null |
	*
	*/
	export function valueFromASTUntyped(
	valueNode: ValueNode,
	variables?: ?ObjMap<mixed>,
	): mixed {

Moreover it's used by default:

graphql-js/src/type/definition.js

Line 563 in 8aef229

this.parseLiteral = config.parseLiteral || valueFromASTUntyped;

So you don't need to use package for it just do:

 GraphQLScalarType({
  name: 'JSON',
  serialize: (value) => value,
});

[anhldbk]

@IvanGoncharov Thank you for your hint.

But would you please tell me how to properly parse JSON-enabled value into AST? I have to patch astFromValue: https://github.com/graphql/graphql-js/blob/8aef229cb2/src/utilities/astFromValue.js#L139-L140

by adding following lines before L139

if (typeof serialized === 'object' ){
    return {
      kind: _kinds.Kind.OBJECT,
      value: serialized
    };
}

[IvanGoncharov]

@anhldbk Yes, it looks like a bug. We should support scalars that are serialized to complex values.
Can you please open a separate issue for that?