From aab613030d6604f32c96e9d58b88f5e49ad94408 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Julien=20Valverd=C3=A9?= <julien.valverde@mailo.com>
Date: Mon, 23 Mar 2026 19:40:00 +0100
Subject: [PATCH] Fix

---
 packages/effect-fc/src/Lens.ts | 94 ++++++++++++++++++----------------
 1 file changed, 51 insertions(+), 43 deletions(-)

diff --git a/packages/effect-fc/src/Lens.ts b/packages/effect-fc/src/Lens.ts
index 98d16b7..18d10b3 100644
--- a/packages/effect-fc/src/Lens.ts
+++ b/packages/effect-fc/src/Lens.ts
@@ -1,4 +1,4 @@
-import { Effect, Pipeable, Predicate, Readable, Stream, Subscribable, SubscriptionRef } from "effect"
+import { Effect, Pipeable, Predicate, Readable, Stream, Subscribable, type SubscriptionRef } from "effect"
 
 
 export const LensTypeId: unique symbol = Symbol.for("@effect-fc/Lens/Lens")
@@ -8,7 +8,6 @@ export interface Lens<in out A, in out ER = never, in out RR = never, in out EW
 extends Subscribable.Subscribable<A, ER, RR> {
     readonly [LensTypeId]: LensTypeId
 
-    readonly set: (a: A) => Effect.Effect<void, EW, RW>
     readonly modify: <B, E1 = never, R1 = never>(
         f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
     ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>
@@ -23,30 +22,42 @@ extends Pipeable.Class() implements Lens<A, ER, RR, EW, RW> {
     constructor(
         readonly get: Effect.Effect<A, ER, RR>,
         readonly changes: Stream.Stream<A, ER, RR>,
-        readonly set: (a: A) => Effect.Effect<void, EW, RW>,
+        readonly modify: <B, E1 = never, R1 = never>(
+            f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
+        ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>,
     ) {
         super()
     }
-
-    modify<B, E1 = never, R1 = never>(
-        f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
-    ) {
-        return Effect.flatMap(
-            this.get,
-            a => Effect.flatMap(f(a), ([b, next]) => Effect.as(this.set(next), b)
-        ))
-    }
 }
 
 
 export const isLens = (u: unknown): u is Lens<unknown, unknown, unknown, unknown, unknown> => Predicate.hasProperty(u, LensTypeId)
 
 
-export const make = <A, ER, RR, EW, RW>(options: {
-    readonly get: Effect.Effect<A, ER, RR>
-    readonly changes: Stream.Stream<A, ER, RR>
-    readonly set: (a: A) => Effect.Effect<void, EW, RW>
-}): Lens<A, ER, RR, EW, RW> => new LensImpl(options.get, options.changes, options.set)
+export const make = <A, ER, RR, EW, RW>(
+    options: {
+        readonly get: Effect.Effect<A, ER, RR>
+        readonly changes: Stream.Stream<A, ER, RR>
+    } & (
+        | {
+            readonly modify: <B, E1 = never, R1 = never>(
+                f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
+            ) => Effect.Effect<B, ER | EW | E1, RR | RW | R1>
+        }
+        | { readonly set: (a: A) => Effect.Effect<void, EW, RW> }
+    )
+): Lens<A, ER, RR, EW, RW> => new LensImpl<A, ER, RR, EW, RW>(
+    options.get,
+    options.changes,
+    Predicate.hasProperty(options, "modify")
+        ? options.modify
+        : <B, E1 = never, R1 = never>(
+            f: (a: A) => Effect.Effect<readonly [B, A], E1, R1>
+        ) => Effect.flatMap(
+            options.get,
+            a => Effect.flatMap(f(a), ([b, next]) => Effect.as(options.set(next), b)
+        )),
+)
 
 /**
  * Creates a `Lens` that directly proxies a `SubscriptionRef`.
@@ -56,52 +67,47 @@ export const fromSubscriptionRef = <A>(
 ): Lens<A, never, never, never, never> => make({
     get: ref.get,
     get changes() { return ref.changes },
-    set: a => SubscriptionRef.set(ref, a),
+    modify: ref.modifyEffect,
 })
 
 
 export const map = <A, ER, RR, EW, RW, B>(
     self: Lens<A, ER, RR, EW, RW>,
     get: (a: A) => B,
-    set: (b: B) => A,
+    set: (b: B, parent: A) => A,
 ): Lens<B, ER, RR, EW, RW> => {
-    make({
-        get: Effect.map(self.get, get),
-        changes: Stream.map(self.changes, get),
-
-    })
-    const get = Effect.map(self.get, f)
-    const changes = Stream.map(self.changes, f)
-    const set = (b: B) => self.set(g(b))
-
-    const out = new LensImpl(get, changes, set)
-
-    ;(out as any).modify = <C, E1 = never, R1 = never>(
+    const getEffect = Effect.map(self.get, get)
+    const changes = Stream.map(self.changes, get)
+    const modify = <C, E1 = never, R1 = never>(
         h: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
     ) => self.modify((a: A) => {
-        const b = f(a)
-        return Effect.flatMap(h(b), ([c, bNext]) => Effect.succeed([c, g(bNext)] as const))
+        const b = get(a)
+        return Effect.flatMap(h(b), ([c, bNext]) => Effect.succeed([c, set(bNext, a)] as const))
     })
 
-    return out
+    return make({
+        get: getEffect,
+        changes,
+        modify,
+    })
 }
 
 export const mapEffect = <A, ER, RR, EW, RW, B, EGet = never, RGet = never, ESet = never, RSet = never>(
     self: Lens<A, ER, RR, EW, RW>,
     getF: (a: A) => Effect.Effect<B, EGet, RGet>,
-    setF: (b: B) => Effect.Effect<A, ESet, RSet>,
+    setF: (b: B, parent: A) => Effect.Effect<A, ESet, RSet>,
 ): Lens<B, ER | EGet, RR | RGet, EW | ESet, RW | RSet> => {
     const get = Effect.flatMap(self.get, getF)
     const changes = Stream.mapEffect(self.changes, getF)
-    const set = (b: B) => Effect.flatMap(setF(b), a => self.set(a))
-
-    const out = new LensImpl(get, changes, set)
-
-    ;(out as any).modify = <C, E1 = never, R1 = never>(
+    const modify = <C, E1 = never, R1 = never>(
         h: (b: B) => Effect.Effect<readonly [C, B], E1, R1>
-    ) => self.modify((a: A) => Effect.flatMap(getF(a), b => Effect.flatMap(h(b), ([c, bNext]) => Effect.flatMap(setF(bNext), nextA => Effect.succeed([c, nextA] as const)))))
+    ) => self.modify((a: A) => Effect.flatMap(getF(a), b => Effect.flatMap(h(b), ([c, bNext]) => Effect.flatMap(setF(bNext, a), nextA => Effect.succeed([c, nextA] as const)))))
 
-    return out
+    return make({
+        get,
+        changes,
+        modify,
+    })
 }
 
 export const unwrap = <A, ER, RR, EW, RW, E1, R1>(
@@ -109,5 +115,7 @@ export const unwrap = <A, ER, RR, EW, RW, E1, R1>(
 ): Lens<A, ER | E1, RR | R1, EW | E1, RW | R1> => make({
     get: Effect.flatMap(effect, l => l.get),
     changes: Stream.unwrap(Effect.map(effect, l => l.changes)),
-    set: a => Effect.flatMap(effect, l => l.set(a)),
+    modify: <B, E2 = never, R2 = never>(
+        f: (a: A) => Effect.Effect<readonly [B, A], E2, R2>
+    ) => Effect.flatMap(effect, l => l.modify(f)),
 })