Made Schema.brand not any-fy piped schemas

[nikelborm]

Type

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

When Schema.brand was extracted into a variable, other schemas, piped through that variable, resulted in Schema.Any type.

Before

const UserIdBrandSchema = Schema.brand("UserId")
const UserIdSchema = pipe(Schema.Number, UserIdBrandSchema)
//    ^? Schema.brand<Schema.Schema.Any, "UserId">

After

const UserIdBrandSchema = Schema.brand("UserId")
const UserIdSchema = pipe(Schema.Number, UserIdBrandSchema)
//    ^? Schema.brand<typeof Schema.Number, "UserId">

[changeset-bot]

🦋 Changeset detected

Latest commit: 4ab07d6

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 35 packages

Name	Type
effect	Patch
@effect/cli	Patch
@effect/cluster	Patch
@effect/experimental	Patch
@effect/opentelemetry	Patch
@effect/platform-browser	Patch
@effect/platform-bun	Patch
@effect/platform-node-shared	Patch
@effect/platform-node	Patch
@effect/platform	Patch
@effect/printer-ansi	Patch
@effect/printer	Patch
@effect/rpc	Patch
@effect/sql-clickhouse	Patch
@effect/sql-d1	Patch
@effect/sql-drizzle	Patch
@effect/sql-kysely	Patch
@effect/sql-libsql	Patch
@effect/sql-mssql	Patch
@effect/sql-mysql2	Patch
@effect/sql-pg	Patch
@effect/sql-sqlite-bun	Patch
@effect/sql-sqlite-do	Patch
@effect/sql-sqlite-node	Patch
@effect/sql-sqlite-react-native	Patch
@effect/sql-sqlite-wasm	Patch
@effect/sql	Patch
@effect/typeclass	Patch
@effect/vitest	Patch
@effect/workflow	Patch
@effect/ai	Patch
@effect/ai-amazon-bedrock	Patch
@effect/ai-anthropic	Patch
@effect/ai-google	Patch
@effect/ai-openai	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[nikelborm]

If anybody else needs a dirty patch (because I didn't change source maps, and so all usages of "go to definition" in Schema file will be a bit shifted) for node_modules folder:

patches/[email protected]

diff --git a/dist/dts/Schema.d.ts b/dist/dts/Schema.d.ts
index 15d098e7573a5f64135fdde3481fbba286514fb2..753d93b41b09ae09c73aa3e79ae2ee4574d1c741 100644
--- a/dist/dts/Schema.d.ts
+++ b/dist/dts/Schema.d.ts
@@ -1591,7 +1591,7 @@ export interface brand<S extends Schema.Any, B extends string | symbol> extends
  * @category branding
  * @since 3.10.0
  */
-export declare const brand: <S extends Schema.Any, B extends string | symbol>(brand: B, annotations?: Annotations.Schema<Schema.Type<S> & Brand<B>>) => (self: S) => brand<S, B>;
+export declare const brand: <S extends Schema.Any, B extends string | symbol>(brand: B, annotations?: Annotations.Schema<Schema.Type<S> & Brand<B>>) => <SubS extends S>(self: SubS) => brand<SubS, B>;
 /**
  * @category combinators
  * @since 3.10.0
diff --git a/src/Schema.ts b/src/Schema.ts
index ab2e298242e0d2e8a93eceb0f6b7622efcf2a8f4..6e024c127e33f1ee024b45c18463470548ae804d 100644
--- a/src/Schema.ts
+++ b/src/Schema.ts
@@ -3403,7 +3403,7 @@ export const brand = <S extends Schema.Any, B extends string | symbol>(
   brand: B,
   annotations?: Annotations.Schema<Schema.Type<S> & Brand<B>>
 ) =>
-(self: S): brand<S, B> => {
+<SubS extends S>(self: SubS): brand<SubS, B> => {
   const annotation: AST.BrandAnnotation = option_.match(AST.getBrandAnnotation(self.ast), {
     onNone: () => [brand],
     onSome: (brands) => [...brands, brand]

[nikelborm]

Hello @gcanti!

May I please ask you for a few minutes of your time dedicated to the review of this tiny PR? I would greatly appreciate your attention and time, if you have the capacity and available resources for this effort.

If you would like me to add it to effect-smol too, I can do it too

[gcanti]

@nikelborm actually I have been thinking about this for a few days, since it would be useful (for all APIs, not just for brand).

As for the implementation in this PR, it doesn't play well with annotations:

import { pipe, Schema } from "effect"

const UserIdBrandSchema = Schema.brand("UserId", {
  examples: ["a"] // UserIdBrandSchema should only apply to strings now
})

const UserIdSchema = pipe(
  Schema.Number, // no error
  UserIdBrandSchema
)

const UserIdSchema2 = pipe(
  Schema.Number, // no error
  Schema.brand("UserId", {
    examples: ["a"]
  })
)

[nikelborm]

for all APIs, not just for brand

I noticed that too. The same thing is in Schema.compose too.

const addAsdField = Schema.compose(Schema.Struct({
  asd: Schema.String
}))

// addAsdField: (from: Schema.Schema.Any) => Schema.transform<Schema.Schema.Any, Schema.Struct<{
//     asd: typeof Schema.String;
// }>>

// Has hardcoded Schema.Schema.Any here


const TestSchema = Schema.asSchema(pipe(
  Schema.Struct({sdf: Schema.Number}),
  addAsdField
))

// TestSchema: Schema.Schema<
//   { readonly asd: string; },
//   any,
//   unknown
// >

So it's generally applicable that there are 2 kinds of ways of writing generics. I noticed that some generics provide better inference in pipes, and some outside of pipes, and the user has to either choose, or there should be some clever thing that automatically determines if it is inside the pipe or outside. That's what I'm talking about: #4148 (comment)

The important change is on lines 12-14:

So in the end, could you please help me better understand how I interpret your response?

I have a few interpretations in mind:

1. This PR won't fit well into the project just by itself, even if I resolve the problem with annotations, and you want me to find a way to fix it generally for every place where this kind of bug occurs.
2. Same as above, but you want to fix the problem yourself, because you know the codebase better
3. I have to fix the problem with annotations, because that's the only blocker for now, preventing the PR from being merged
4. You want to start a discussion on how this problem could be solved generally
5. You want me to close the PR and wait because it may/will be fixed by effect-smol

And thank you for the feedback! ❤️

[nikelborm]

Also, I figured there's even yet another thing that could be done:

Writing tests to catch that case.

import { pipe, Schema } from "effect"

const UserIdBrandSchema = Schema.brand("UserId", {
  examples: ["a"] // UserIdBrandSchema should only apply to strings now
})

const UserIdSchema = pipe(
  Schema.Number, // no error
  UserIdBrandSchema
)

const UserIdSchema2 = pipe(
  Schema.Number, // no error
  Schema.brand("UserId", {
    examples: ["a"]
  })
)

Because the CI says it's all clear, and it wasn't caught.

[gcanti]

As a baseline since Schema.brand is meant to be used in a pipeline, this should raise an error (as it currently does in main):

const UserIdSchema2 = pipe(
  Schema.Number,
  Schema.brand("UserId", {
    examples: ["a"] // should raise an error
  })
)

(I added a type-level test for this)

Regarding the general issue, I have not found a way to achieve this behavior while also being able to define a generic function that applies a brand (within the same API). I have not found a solution for this in v4 either, although this is less of a problem there because brands are reified instead of being schema combinators, which makes them easier to reuse.

Maybe I just have not found the right trick yet, any attempt to solve the issue is welcome.