Applying patches returns empty array after update to v1.11.0

[hastebrot]

• Issue: Applying patches returns empty array after update to v1.11.0.

Works with immer v1.10.5. Does not work with immer v1.11.0 and v1.12.0.

Code to reproduce (in TypeScript):

import { produce, applyPatches } from "immer"

let patches = [] as any[]
const state0: { a: number, b?: number } = { a: 1 }
const state1 = produce(state0, (draft) => { draft.b = 9 }, (p) => { patches.push(...p) })
const state2 = produce(state1, (draft) => { draft.a = 3 }, (p) => { patches.push(...p) })
const state3 = produce(state2, (draft) => { draft.b = 99 }, (p) => { patches.push(...p) })
const state4 = produce(state3, (draft) => { draft.a = 5 }, (p) => { patches.push(...p) })

console.log(patches)
// [ { op: 'add', path: [ 'b' ], value: 9 },
//   { op: 'replace', path: [ 'a' ], value: 3 },
//   { op: 'replace', path: [ 'b' ], value: 99 },
//   { op: 'replace', path: [ 'a' ], value: 5 } ]

produce(state0, (draft) => { applyPatches(draft, patches) }, (p) => { patches = p })

console.log(patches)
// [ { op: 'add', path: [ 'b' ], value: 99 },
//   { op: 'replace', path: [ 'a' ], value: 5 } ]

console.log(state0)
// { a: 1 }
console.log(state4)
// { a: 5, b: 99 }

Code based on https://medium.com/@dedels/using-immer-to-compress-immer-patches-f382835b6c69.

Expected behavior: It logs the patches like in the comments.

Observed behavior: The second logged patches is an empty array [].

[hastebrot]

Closing issue. I fixed it by returning the new draft after applying the patches.

Working example for immer v1.12.0 (in TypeScript):

import { produce, applyPatches } from "immer"

let patches = [] as any[]
const state0: { a: number, b?: number } = { a: 1 }
const state1 = produce(state0, (draft) => { draft.b = 9 }, (p) => { patches.push(...p) })
const state2 = produce(state1, (draft) => { draft.a = 3 }, (p) => { patches.push(...p) })
const state3 = produce(state2, (draft) => { draft.b = 99 }, (p) => { patches.push(...p) })
const state4 = produce(state3, (draft) => { draft.a = 5 }, (p) => { patches.push(...p) })

console.log(patches)
// [ { op: 'add', path: [ 'b' ], value: 9 },
//   { op: 'replace', path: [ 'a' ], value: 3 },
//   { op: 'replace', path: [ 'b' ], value: 99 },
//   { op: 'replace', path: [ 'a' ], value: 5 } ]

const state5 = produce(state0,
  (draft) => applyPatches(draft, patches),
  (p) => { patches = p }
)

console.log(patches)
// [ { op: 'replace', path: [], value: { a: 5, b: 99 } } ]

console.log(state0)
// { a: 1 }
console.log(state4)
// { a: 5, b: 99 }
console.log(state5)
// { a: 5, b: 99 }

[aleclarson]

This is an unintended breaking change. Thanks for reporting!

9a2e756 fixed a bug in #282, which is why v1.11.0+ is where this occurs. The applyPatches function is actually a curried producer, which is why it's affected by that PR.

I'm going to change applyPatches to mutate the draft like it did in v1.10.5 and under.

[aleclarson]

In v1.12.1, the applyPatches function now mutates Immer drafts instead of producing a copy.
Note: It still creates a copy when a normal object is passed to it.

[aleclarson]

🎉 This issue has been resolved in version 1.12.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀