Effect CommunityEC
Effect Community•5mo ago
jkomyno

Issues with Default Values in Prisma Config Schema Using Effect-Smol Library

Hello, I stumbled into some problems while trying to expand the @prisma/config effect/Schema definitions with union types with default values.

For context, I want to parse one of the two alternatives in SchemaEngineConfig
type SchemaEngineConfig =
  | {
    engine: 'classic', // this should be the default value, if not specified
    datasource?: { /* ... */}
  | {
    engine: 'js',
    adapter: async () => { /* ... */}
  }

type PrismaConfig = {
  // ...
} & SchemaEngineConfig

and have effect/Schema parse the default { engine: 'classic', datasource: undefined } value when the user doesn't specify any SchemaEngineConfig.

I can't find a way to reliable set default constructors in Schema.Union values that are merged into a Schema.Struct. I heard that effect-smol makes things simpler in that regard, so I decided to try the new APIs out (https://pkg.pr.new/Effect-TS/effect-smol/effect@73e2109).

It seems that piping Schema.withConstructorDefault to a Struct breaks Struct.mapFields, while piping it to a TaggedUnion breaks Union.mapMembers. Chances are I'm holding something wrong. I can only get the code to compile and run when no Schema.withConstructorDefault is used, but that implies I'm not getting the default value I wanted.

Here's a self-contained script with what I tried, with TODO comments: https://gist.github.com/jkomyno/30862bd7d0630d2a861538fcb843dc92

Any help is appreciated 🤝
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