Registry / babel-plugin-parameter-decorator

babel-plugin-parameter-decorator

library1.0.16jsnpmunverified

A Babel plugin that transforms function parameter decorators to behave like TypeScript parameter decorators. Current stable version is 1.0.16, with infrequent releases. It enables parameter decorators on constructor parameters and method parameters when using Babel with legacy decorator support. Unlike TypeScript's built-in support, this plugin requires the separate `@babel/plugin-proposal-decorators` with `legacy: true` and optionally `@babel/plugin-proposal-class-properties`. It is the only dedicated Babel plugin for parameter decorator transformation as of 2024, filling a gap left by other decorator plugins. Works with both JavaScript and TypeScript via Babel presets.

npm install babel-plugin-parameter-decorator

github ↗package ↗

INSTALL

IMPORT

SIG · BABEL-PLUGIN-PARAM

babel-plugin-parameter-decorator

javascriptv1.0.16

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

babel-plugin-parameter-decorator

✓ // in .babelrc or babel.config.js { "plugins": [ ["@babel/plugin-proposal-decorators", { "legacy": true }], "babel-plugin-parameter-decorator" ] }

✗ { "plugins": ["babel-plugin-parameter-decorator"] // missing @babel/plugin-proposal-decorators }

This plugin is a Babel plugin, not a JavaScript module import. It is used only in Babel configuration. Must be placed after the decorators plugin.

Shows how to install, configure Babel with plugin-proposal-decorators (legacy mode) and this plugin, and then transpile a class with parameter decorators.

// Install dependencies // npm install --save-dev @babel/core @babel/cli @babel/plugin-proposal-decorators babel-plugin-parameter-decorator // .babelrc { "plugins": [ ["@babel/plugin-proposal-decorators", { "legacy": true }], "babel-plugin-parameter-decorator" ] } // input.js function required(key) { return function (target, propertyKey, parameterIndex) { const metadata = `meta_${propertyKey}`; target[metadata] = [ ...(target[metadata] || []), { index: parameterIndex, key } ]; }; } function validate(target, property, descriptor) { const fn = descriptor.value; descriptor.value = function(...args) { const metadata = `meta_${property}`; target[metadata].forEach(function(meta) { if (args[meta.index] === undefined) { throw new Error(`${meta.key} is required`); } }); return fn.apply(this, args); }; return descriptor; } class Greeter { constructor(message) { this.greeting = message; } @validate greet(@required('name') name) { return "Hello " + name + ", " + this.greeting; } } // Run: npx babel input.js --out-file output.js

Debug

Known issues

gotchaPlugin must be placed after @babel/plugin-proposal-decorators in plugins array.

fix

Ensure order: [['@babel/plugin-proposal-decorators', {legacy: true}], 'babel-plugin-parameter-decorator']

affects: *

gotchaIf using @babel/preset-typescript, TypeScript-only imports used in decorators will be removed by default, breaking references.

fix

Set 'onlyRemoveTypeImports' to true in preset options: ['@babel/preset-typescript', { onlyRemoveTypeImports: true }]

affects: *

gotchaRequires @babel/plugin-proposal-decorators with legacy: true; the newer '2023-01' or '2023-11' decorator proposal is not supported.

fix

Use legacy: true (the Stage 1 decorators proposal).

affects: *

Errors

Common errors & fixes

Error: [BABEL] unknown: Decorators are not enabled.

Missing @babel/plugin-proposal-decorators plugin in Babel config.

fix

Add ["@babel/plugin-proposal-decorators", { "legacy": true }] before babel-plugin-parameter-decorator.

TypeError: Cannot read properties of undefined (reading 'forEach')

Parameter decorator used on a method without the companion method decorator (e.g., @validate) writing metadata.

fix

Ensure a method decorator writes the metadata that the parameter decorator expects; example uses @validate.

Error: Parameter decorator is not a function

Incorrect import or invalid decorator function; parameter decorator must return a function that takes (target, propertyKey, parameterIndex).

fix

Define parameter decorator correctly: function decorator(key) { return function(target, propKey, paramIndex) { ... }; }

Upgrade

Version history

1.0.16latest on npm

Audit

Dependencies

@babel/plugin-proposal-decoratorsrequiredRequired as a peer/ runtime dependency; must be configured with legacy: true for this plugin to work.

Agent activity

14 hits · last 30 days

node

Resources

githubhttps://github.com/WarnerHooh/babel-plugin-parameter-decorator ↗

packagehttps://www.npmjs.com/package/babel-plugin-parameter-decorator ↗