babel-plugin-transform-flow-enums

0.0.2 verified Sat Apr 25 auth: no javascript

Transforms Flow Enum declarations (EnumDeclaration) into runtime calls using the flow-enums-runtime package. Current stable version is 0.0.2. Updated as part of Flow releases (e.g., v0.308.0 changed enum AST node shape). This plugin is essential for projects using Flow Enums and Babel, providing a compile-time transformation. Differentiators: official Facebook package, tightly coupled with Flow's enum syntax and runtime, supports boolean/number/string/symbol/bigint enum types. Requires @babel/plugin-syntax-flow with {enums: true} and the flow-enums-runtime package.

Common errors

error SyntaxError: Support for the experimental syntax 'Flow' isn't currently enabled ↓

cause Missing @babel/plugin-syntax-flow plugin.

fix

Add '@babel/plugin-syntax-flow' (with { enums: true } if using enums) to your Babel plugins.

error Cannot find module 'flow-enums-runtime' ↓

cause Missing runtime dependency in transformed code.

fix

Run 'npm install flow-enums-runtime' and ensure it's in your dependencies.

error Error: [BABEL] unknown: .plugins[1][1] must be an object, false, or undefined (BCP 6) ↓

cause Passing options as a string instead of an array or object.

fix

Use array form for plugin options: ['babel-plugin-transform-flow-enums', { getRuntime: ... }]

Warnings

breaking Flow v0.308.0 changed the enum AST node structure from separate body types (EnumBooleanBody, etc.) to a single EnumBody node. Ensure your plugin version is compatible with your Flow version. ↓

fix Update both plugin and Flow to compatible versions. If using Flow >=0.308.0, ensure babel-plugin-transform-flow-enums is updated to support new AST.

gotcha The @babel/plugin-syntax-flow plugin must be configured with {enums: true} as the plugin option array, not as a top-level Babel option. ↓

fix Correct configuration: plugins: [['@babel/plugin-syntax-flow', { enums: true }]]

gotcha The runtime dependency flow-enums-runtime must be installed in the project; this plugin will require it at runtime in the transformed code. ↓

fix Add flow-enums-runtime to your project dependencies: npm install flow-enums-runtime

gotcha This plugin only handles EnumDeclaration nodes; other flow enum-related syntax (e.g., enum member access) is left for the runtime. ↓

fix No fix needed; ensure flow-enums-runtime is used in your project.

Install

npm install babel-plugin-transform-flow-enums

yarn add babel-plugin-transform-flow-enums

pnpm add babel-plugin-transform-flow-enums

Imports

default export (plugin function)

wrong

import plugin from 'babel-plugin-transform-flow-enums'; // Wrong: plugin is CommonJS, not ESM

correct

module.exports = require('babel-plugin-transform-flow-enums');

This package is CommonJS-only without ESM support.

babel.config.js usage

wrong

plugins: [['babel-plugin-transform-flow-enums', { getRuntime: ... }]] // Wrong: passing options as array is correct only when options are provided; the string form without options is also valid

correct

plugins: ['babel-plugin-transform-flow-enums']

Options can be provided as the second element of an array in the plugin list.

getRuntime option

wrong

plugins: [['babel-plugin-transform-flow-enums', { getRuntime: 'flow-enums-runtime' }]] // Wrong: getRuntime must be a function, not a string

correct

plugins: [['babel-plugin-transform-flow-enums', { getRuntime: (t) => t.memberExpression(t.identifier('require'), t.stringLiteral('flow-enums-runtime')) }]]

The getRuntime option receives Babel types (t) and must return a Babel AST node that references the runtime.

Quickstart

Set up Babel to transform Flow Enums using the required syntax plugin and runtime.

// Install dependencies:
// npm install --save-dev babel-plugin-transform-flow-enums @babel/plugin-syntax-flow flow-enums-runtime

// babel.config.js file:
module.exports = {
  plugins: [
    ['@babel/plugin-syntax-flow', { enums: true }],
    'babel-plugin-transform-flow-enums'
  ]
};

// Input file (test.js):
// @flow
enum Status { Active, Inactive }

// After transform:
// const Status = require('flow-enums-runtime').create(['Active', 'Inactive']);