Unsupported schema Error while applying Partial to Schema class

[bhvngt]

What version of Effect is running?

3.4.3

What steps can reproduce the bug?

import { Schema } from "@effect/schema";

class Todo extends Schema.Class<Todo>("Todo")({
  id: Schema.Number,
  title: Schema.String,
  completed: Schema.Boolean
}) {}

const CreateTodoParams = Todo.pipe(Schema.omit("id"));
type CreateTodoParams = Schema.Schema.Type<typeof CreateTodoParams>;

const UpdateTodoParams = Schema.partial(Todo, { exact: true }); // throws Unsupported schema schema (Transformation): (Todo (Encoded side) <-> Todo)
type UpdateTodoParams = Schema.Schema.Type<typeof UpdateTodoParams>;

What is the expected behavior?

It should not throw any error. Also it is unionising properties with undefined for UpdateTodoParams to

const UpdateTodoParams: Schema.SchemaClass<{
readonly id?: number | undefined;
readonly title?: string | undefined;
readonly completed?: boolean | undefined;
}, {
readonly id?: number | undefined;
readonly title?: string | undefined;
readonly completed?: boolean | undefined;
}, never>

even though {exact: true} is passed. My understanding is that it should opt-out of that.

What do you see instead?

See following error in the terminal

Unsupported schema
schema (Transformation): (Todo (Encoded side) <-> Todo)
	at Module.partial ./node_modules/.pnpm/@effect+schema@0.68.10_effect@3.4.3/node_modules/@effect/schema/src/AST.ts:2245
	at Module.apply ./node_modules/.pnpm/@effect+schema@0.68.10_effect@3.4.3/node_modules/@effect/schema/src/Schema.ts:2855
	at Module.<anonymous> ./node_modules/.pnpm/effect@3.4.3/node_modules/effect/src/Function.ts:85

Additional information

[gcanti]

It raises an error because the Schema.Class API implicitly defines a transformation, specifically from:

Schema.Struct({
  id: Schema.Number,
  title: Schema.String,
  completed: Schema.Boolean
})

to Todo in this case, and transformations are not supported by Schema.partial.

However, this should work:

const UpdateTodoParams = Schema.partial(Schema.Struct(Todo.fields), { exact: true })

[bhvngt]

Got it. Thank you for your reply.

Tried your solution and that stopped the error from occurring. However, I was expecting the non-unionised type, since exact: true is passed as an option to opt out of unionisation. However, types are still unionised. Am I missing something here?

[gcanti]

Do you have the exactOptionalPropertyTypes option enabled in your tsconfig?

[bhvngt]

Yep that was the missing piece. Sorry, I overlooked the documentation here.

Thanks you very much for this really powerful and composable library.