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Schema: idiomatic way to encode against a type-erased `Schema.Top` (codec services show as `unknown` in the requirements channel)?

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Valutazione

Difficoltà
5/5
Tempo stimato
Più di una settimana
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35/100
Tipo di issue
Funzionalità
Chiarezza
Abbastanza chiara
Stato di attività
Tranquilla
Stack tecnologico
typescript
Ambito
api

Direzione di ricerca

Start with the Schema.Top, Schema.toCodecJson, Schema.encodeUnknownEffect, encodeUnknownExit, and encodeUnknownResult APIs, then run the linked reproduction with bun install and bun run repro. Compare the reported R=unknown and R=never assertions and runtime check; done would require an agreed idiomatic way to encode or decode service-free type-erased schemas without an unsafe cast.

Scritto dal modello di indicizzazione a partire dal testo della issue.

Descrizione

This is a usage/idiom question about encoding against type-erased schemas.

When you only have a type-erased Schema.Top — e.g. from RPC dynamic dispatch, heterogeneous registries, or plugin systems where the concrete schema type is lost — encoding a value against it as JSON surfaces unknown in the requirements (R) channel:

declare const erased: Schema.Top
const eff = Schema.encodeUnknownEffect(Schema.toCodecJson(erased))(value)
//    eff: Effect<Json, SchemaError, unknown>   // <- unknown in R

Schema.Top types DecodingServices/EncodingServices as unknown, and toCodecJson + encodeUnknownEffect forward them into R. @effect/language-service flags it as anyUnknownInErrorContext (TS377030, "unknown in the requirements channel"). But such schemas are plain data — they need no codec services (the repro verifies this at runtime).

The only clean fix we found is an unsafe cast asserting the (true) never service channels:

Schema.toCodecJson(erased as Schema.Codec<unknown, unknown, never, never>)
//    -> Effect<Json, SchemaError, never>

We confirmed encodeUnknownExit / encodeUnknownResult (which return Exit/Result with no R channel) don't avoid the cast — their ConstraintEncoder<unknown> bound requires EncodingServices extends never, which Schema.Top doesn't satisfy.

Question: is casting the service channels the idiomatic way to encode/decode against a Schema.Top known to need no services, or is there a cleaner, more Effect-native API for this (a service-erasing combinator, an encode variant that ignores services, a better way to type-erase RPC schemas, etc.)?

Reproduction

https://github.com/schickling-repros/2026-07-effect-erased-schema-services

bun install
bun run repro   # tsc type-assertions (R=unknown vs R=never) + a runtime check

Versions

  • effect: 4.0.0-beta.98
  • @effect/language-service: anyUnknownInErrorContext (TS377030)

Context: this arises encoding RPC exit/payload schemas after dynamic dispatch erases them to Schema.Top — a follow-on to #6064 (which exposed successSchema but not the service-typing question).

Posted on behalf of @schickling
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agent_name 🌲 cl1-pine
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agent_tool_version 2.1.206
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skills_manifest /nix/store/jn6r0r7r59x3a525jch4pwzwykszqp60-agent-skills-corpus/share/agent-skills/manifest.json
worktree livestore/schickling/2026-07-17-refactor
machine dev3
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