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[@vue/reactivity] watch() doesn't accept TS generics #13807

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#13840
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[@vue/reactivity] watch() doesn't accept TS generics#13807
#13840
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scope: types
@Maxim-Mazurok

Description

@Maxim-Mazurok
Maxim-Mazurok
opened on Aug 25, 2025

Vue version

3.5.20

Link to minimal reproduction

N/A

Steps to reproduce

watch() from @vue/reactivity doesn't accept generic <T> type arguments, so the new/old value types are any:

core/packages/reactivity/src/watch.ts

Line 120 in 24fccb4

export function watch(

What is expected?

Please let's add similar generics as @vue/runtime-core:

core/packages/runtime-core/src/apiWatch.ts

Lines 87 to 126 in 24fccb4

export function watch<T, Immediate extends Readonly<boolean> = false>(
source: WatchSource<T>,
cb: WatchCallback<T, MaybeUndefined<T, Immediate>>,
options?: WatchOptions<Immediate>,
): WatchHandle
// overload: reactive array or tuple of multiple sources + cb
export function watch<
T extends Readonly<MultiWatchSources>,
Immediate extends Readonly<boolean> = false,
>(
sources: readonly [...T] | T,
cb: [T] extends [ReactiveMarker]
? WatchCallback<T, MaybeUndefined<T, Immediate>>
: WatchCallback<MapSources<T, false>, MapSources<T, Immediate>>,
options?: WatchOptions<Immediate>,
): WatchHandle
// overload: array of multiple sources + cb
export function watch<
T extends MultiWatchSources,
Immediate extends Readonly<boolean> = false,
>(
sources: [...T],
cb: WatchCallback<MapSources<T, false>, MapSources<T, Immediate>>,
options?: WatchOptions<Immediate>,
): WatchHandle
// overload: watching reactive object w/ cb
export function watch<
T extends object,
Immediate extends Readonly<boolean> = false,
>(
source: T,
cb: WatchCallback<T, MaybeUndefined<T, Immediate>>,
options?: WatchOptions<Immediate>,
): WatchHandle
// implementation
export function watch<T = any, Immediate extends Readonly<boolean> = false>(

Thank you!

What is actually happening?

Image

System Info

System:
    OS: Linux 6.6 Ubuntu 24.04.3 LTS 24.04.3 LTS (Noble Numbat)
    CPU: (20) x64 12th Gen Intel(R) Core(TM) i9-12900H
    Memory: 24.99 GB / 31.18 GB
    Container: Yes
    Shell: 5.2.21 - /bin/bash
  Binaries:
    Node: 24.6.0 - ~/.nvm/versions/node/v24.6.0/bin/node
    npm: 11.5.1 - ~/.nvm/versions/node/v24.6.0/bin/npm
    pnpm: 9.4.0 - ~/.local/share/pnpm/pnpm
  Browsers:
    Chrome: 139.0.7258.138

Any additional comments?

Using in NodeJS environment, not for FE

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