We should split reader.ts into several artifacts

[rbalicki2]

Problem

• Currently, reader artifacts contain: the generated TypeScript __param type, the generated __outputType type, and the reader AST.
• If a resolver is unreachable from an entrypoint, we do not need to generate the reader AST. But we do need to generate the types. So, we generate unneeded reader ASTs.
• If the resolver is never selected by another resolver and is not an entrypoint, we do not need to generate the output type. So, we generate some unneeded output types.
• However, we need to define a __param type for all user-defined resolvers, because it is used by iso.ts. We currently generate unneeded __param types for __refetch artifacts (though, seemingly not for magic mutation fields.)

Note: the output and param types that we generate that are not needed are not as big of a deal as the unneeded reader AST, because:

• output types are easy to create
• __refetch fields are rarer
  So, if not generating the output and param types adds complexity, we can punt on it.

Solution

• So, instead, we should split reader.ts into reader.ts (containing the reader AST and reader artifact), param_type.ts and output_type.ts.

Details

• Type/field/param_type.ts should import the output_type of all selected resolvers and export the param type
• Type/field/output_type.ts should contain the ResolverReadOutType (e.g. export type Query__HomeRoute__outputType = (React.FC<ExtractSecondParam<typeof resolver>>);) and nothing else.
• Type/field/reader.ts should define the reader AST. It should import the user-defined exported resolver function (i.e. export const pet_stats_card = iso(...)). It should import the param and output type. It should define and export the artifact.

Follow ups:

• We should only generate types, and not reader ASTs, for unreachable client fields
• Maybe this has some implication for __refetch fields. That seems to work correctly now, but it would be worth double checking whether we can simplify things.
• I'm hoping that this results in cleaner code, which will make it easier to do things like asynchronously import JavaScript (see Split entrypoint.ts artifact into two artifacts: query text and normalization AST #33)

[ismajl-ramadani]

Can I take this?

[rbalicki2]

Closed by d629a5b