test(opencode): use filesystem service accessors

packages/core/src/filesystem.ts

@@ -7,6 +7,43 @@ import { Effect, FileSystem, Layer, Schema, Context } from "effect"
 import type { PlatformError } from "effect/PlatformError"
 import { Glob } from "./util/glob"
 
+type EffectMethod = (...args: ReadonlyArray<never>) => Effect.Effect<unknown, unknown, unknown>
+
+type ServiceUse<Identifier, Shape> = {
+  readonly [Key in keyof Shape as Shape[Key] extends EffectMethod ? Key : never]: Shape[Key] extends (
+    ...args: infer Args
+  ) => infer Return
+    ? Args extends ReadonlyArray<unknown>
+      ? Return extends Effect.Effect<infer A, infer E, infer R>
+        ? (...args: Args) => Effect.Effect<A, E, R | Identifier>
+        : never
+      : never
+    : never
+}
+
+const serviceUse = <Identifier, Shape>(tag: Context.Service<Identifier, Shape>) => {
+  // This is the only dynamic boundary: TypeScript knows the accessor shape,
+  // but Proxy property names are runtime values.
+  const access = new Proxy(
+    {},
+    {
+      get: (_, key) => {
+        if (typeof key !== "string") return undefined
+        return (...args: unknown[]) =>
+          tag.use((service) => {
+            // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- Proxy keys are checked at runtime.
+            const method = service[key as keyof Shape]
+            if (typeof method !== "function") return Effect.die(new Error(`Service method not found: ${key}`))
+            // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- ServiceUse exposes only Effect-returning methods.
+            return (method as (...args: unknown[]) => Effect.Effect<unknown, unknown, unknown>)(...args)
+          })
+      },
+    },
+  )
+  // oxlint-disable-next-line typescript-eslint/no-unsafe-type-assertion -- Proxy implements the mapped accessor surface lazily.
+  return access as ServiceUse<Identifier, Shape>
+}
+
 export namespace AppFileSystem {
   export class FileSystemError extends Schema.TaggedErrorClass<FileSystemError>()("FileSystemError", {
     method: Schema.String,
@@ -39,6 +76,8 @@ export namespace AppFileSystem {
 
   export class Service extends Context.Service<Service, Interface>()("@opencode/FileSystem") {}
 
+  export const use = serviceUse(Service)
+
   export const layer = Layer.effect(
     Service,
     Effect.gen(function* () {