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Worklets without captured variables are rejected as "Regular javascript function" when transpiled by react-native-worklets' Babel plugin

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  • ¿Algo no está bien?
#275 0 comentarios 0 reacciones 0 asignados Ver en GitHub

@wn-na ya está trabajando en esto.

Desde el 19/10/2026.

  • #276 de @wn-na — abierto

Evaluación

Dificultad
3/5
Tiempo estimado
1-2 días
Aptitud para principiantes
55/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
cpp, javascript, react-native
Área
backend, mobile

Línea de trabajo

Start with cpp/WKTJsiWorklet.h, especially isDecoratedAsWorklet() and createWorklet(), then trace how JsiObjectWrapper::setFunctionValue() handles a function without __closure. Reproduce with the supplied Babel output: a numeric __workletHash, string __initData.code, and no closure. Done when that no-capture worklet is recognized and invoked successfully while existing captured worklets still work.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Description

When a project uses the Babel plugin from react-native-worklets (the Reanimated 4 worklets package) together with react-native-worklets-core, any 'worklet' function that does not capture any outer variables is not recognized as a worklet by worklets-core.

Calling such a function from inside another worklet that runs on a worklets-core context throws:

Regular javascript function 't' cannot be shared. Try decorating the function with the 'worklet' keyword to allow the javascript function to be used as a worklet.

('t' is just the minified function name in a release bundle.)

We hit this through react-native-filament: EntitySelector's MaterialModifier worklet calls the module-level applyMaterialParameters worklet, which captures nothing, so every model with materialParameters fails on the worklet thread.

Environment

  • react-native: 0.88.0 (New Architecture, Hermes)
  • react-native-worklets-core: 1.6.3
  • react-native-worklets: 0.13.0 (its Babel plugin is active)
  • react-native-filament: 1.9.0 (where we first saw it; 1.11.0 has the same code)
  • Babel plugins: 
    plugins: [
  ['react-native-worklets-core/plugin', { processNestedWorklets: true }],
  'react-native-worklets/plugin',
]

Minimal reproduction

import { Worklets } from 'react-native-worklets-core'

// Captures nothing from the outer scope
const double = (x: number) => {
  'worklet'
  return x * 2
}

const context = Worklets.createContext('repro')

// The worklet passed to runAsync captures `double`
context
  .runAsync(() => {
    'worklet'
    return double(21) // <- throws "Regular javascript function '...' cannot be shared"
  })
  .then(console.log)

If double captures any outer variable (so it gets a __closure), the call works.

What the transpiled code looks like

With the react-native-worklets plugin (0.13.0, and the same in the 0.14 nightlies), a worklet that captures nothing is emitted without __closure, and the hash is a number literal:

var double = function double_Factory([_worklet_123_init_data]) {
  const double = function (x) { return x * 2 }
  double.__workletHash = 123                    // number, not string
  double.__initData = _worklet_123_init_data   // { code: "(function ...)" }
  return double                                // no __closure assignment
}([_worklet_123_init_data])

The plugin only emits __closure when closureVariables.length > 0 (see plugin/index.js), so leaving it out is intended behavior there, not a bug.

Root cause

In cpp/WKTJsiWorklet.h:

  1. isDecoratedAsWorklet() returns true right away only when __workletHash is a string. Otherwise it requires __closure to be present, so a numeric hash with no __closure is treated as a regular function.
  2. createWorklet() returns early when __closure is undefined/null, so even if detection passed, the worklet would not be created.

JsiObjectWrapper::setFunctionValue() then wraps the function in a host function that throws the "cannot be shared" error when called.

Suggested fix

Treat a function as a worklet when __workletHash is a number and __initData.code is a string, and use an empty closure when __closure is missing. Code generated for a worklet with no captures never reads this.__closure, so an empty array is safe.

I have a small patch for this and can open a PR.

Possibly related

#258 reports release builds failing with "is not a Worklet" when the Reanimated plugin and the worklets-core plugin are used together. It might be the same root cause, but I haven't verified that.

Lenguaje dominante
C++
Estrellas
791
Forks
66
Sin PR fusionados en 30 d

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