babel-plugin-coverage

1.0.0 verified Sat Apr 25 auth: no javascript maintenance

A Babel 6.x plugin that instruments JavaScript code with Istanbul-compatible `__coverage__` variables for test coverage collection. v1.0.0 is the latest stable release. This fork of babel-plugin-__coverage__ adds istanbul-style ignore hints and alters statement counting for conditionals. It works with Karma and mocha/nyc without additional tooling. No ongoing development; exists as a legacy solution for projects stuck on Babel 6.

Common errors

error Couldn't find preset "env" relative to directory ↓

cause Missing or misconfigured babel-preset-env in .babelrc

fix

npm install --save-dev babel-preset-env and add "presets": ["env"] to .babelrc

error Error: Plugin/Preset files are not allowed to export objects, only functions. ↓

cause Using a Babel 6 plugin with Babel 7+

fix

Use @babel/plugin-istanbul or downgrade to Babel 6.

error EBADENGINE: Unsupported engine for babel-plugin-coverage@1.0.0 ↓

cause Node.js version incompatible; the package may require older Node

fix

Use Node.js >= 4.0 and <= 10.x (verify package.json engines if present).

Warnings

breaking babel-plugin-coverage only works with Babel 6.x. It is incompatible with Babel 7+. ↓

fix Use @babel/plugin-istanbul for Babel 7+.

gotcha When using with NYC, you must configure NYC not to instrument your code via nyc.include. ↓

fix In package.json, set "nyc": { "include": [ "/" ] } or equivalent.

gotcha This plugin does not generate any coverage report. It only instruments code. You still need a coverage reporter (karma-coverage, nyc). ↓

fix Use karma-coverage or nyc to generate HTML/lcov reports.

deprecated The original babel-plugin-__coverage__ and this fork are effectively in maintenance mode. No new features or updates. ↓

fix Consider migrating to @babel/plugin-istanbul for newer Babel versions and istanbul compatibility.

Install

npm install babel-plugin-coverage

yarn add babel-plugin-coverage

pnpm add babel-plugin-coverage

Imports

default
wrong
```
const coverage = require('babel-plugin-coverage')
```
correct
```
// No default import; use .babelrc config
```
This is a Babel plugin, not imported in user code. Configure in .babelrc under plugins.
plugin
wrong
```
{
  "plugins": [ [ "babel-plugin-coverage", {} ] ]
}
```
correct
```
{
  "plugins": [ "coverage" ]
}
```
In .babelrc, use the short name 'coverage'. The full name also works but is unnecessary.
options
wrong
```
{
  "plugins": [ [ "babel-plugin-coverage", { "ignore": "test" } ] ]
}
```
correct
```
{
  "plugins": [ [ "coverage", { "ignore": "test/" } ] ]
}
```
Options can include 'ignore' (glob pattern) or 'only' (glob pattern). Note: glob patterns should include trailing slash for directories.

Quickstart

Shows basic setup in .babelrc to enable coverage only during test environments.

// .babelrc
{
  "env": {
    "test": {
      "plugins": [ "coverage" ]
    }
  }
}

// Install: npm install --save-dev babel-plugin-coverage
// Then run tests with Karma + karma-coverage or mocha + nyc.