Registry / testing / coverage-istanbul-loader

coverage-istanbul-loader

library3.0.5jsnpmunverified

A Webpack loader that uses Istanbul to add code coverage instrumentation to JavaScript/TypeScript files. Current stable version is 3.0.5. Release cadence is low; last major update was in 2020. Key differentiators include support for modern Istanbul API (istanbul-lib-instrument) and better source map handling compared to the older istanbul-instrumenter-loader. Ships TypeScript definitions. Requires Node >=10 and Webpack 4+. Works with Karma, TypeScript, and custom options.

testing

npm install coverage-istanbul-loader

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · COVERAGE-ISTANBUL-

coverage-istanbul-loader

testingjavascriptv3.0.5

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.

default

✓ import CoverageIstanbulLoader from '@jsdevtools/coverage-istanbul-loader'

✗ const CoverageIstanbulLoader = require('@jsdevtools/coverage-istanbul-loader')

ESM-only since v3. CommonJS require will fail.

loader function

✓ const { default: loader } = require('@jsdevtools/coverage-istanbul-loader')

✗ const loader = require('@jsdevtools/coverage-istanbul-loader')

In CommonJS, must grab .default property.

Webpack rule usage

✓ module.exports = { module: { rules: [ { test: /\.js$/, use: { loader: '@jsdevtools/coverage-istanbul-loader', options: { esModules: true } } } ] } }

✗ use: 'coverage-istanbul-loader' (without @jsdevtools scope)

Full scoped package name required.

Configures Webpack to instrument JavaScript files for code coverage using Istanbul, with modern options.

// webpack.config.js module.exports = { module: { rules: [ { test: /\.js$/, exclude: /node_modules/, use: { loader: '@jsdevtools/coverage-istanbul-loader', options: { esModules: true, produceSourceMap: true } } } ] } }; // Run webpack, output bundle will have coverage instrumentation. // Then run tests with Karma + karma-coverage-istanbul-reporter.

Debug

Known issues

breakingVersion 3.0 is ESM-only. Using require() will fail with 'require() of ES modules not supported'.

fix

Use import or dynamic import(), or downgrade to v2.x.

affects: >=3.0.0

gotchaLoader must be placed before other loaders (like babel-loader) in webpack config to instrument original source.

fix

Ensure this loader is listed last in the 'use' array (i.e., executed first).

affects: >=1.0.0

deprecatedOption 'instrumenter' is deprecated in favor of 'istanbul-lib-instrument' options.

fix

Replace 'instrumenter' with 'istanbul-lib-instrument' options (e.g., 'esModules').

affects: >=3.0.0

gotchaSource maps may not work correctly if options.produceSourceMap is not set to true.

fix

Set produceSourceMap: true in loader options.

affects: >=3.0.0

Errors

Common errors & fixes

Error: Cannot find module '@jsdevtools/coverage-istanbul-loader'

Loader not installed or typo in package name.

fix

npm install @jsdevtools/coverage-istanbul-loader --save-dev

TypeError: loader.run is not a function

Using CommonJS require() on ESM-only v3.

fix

Use dynamic import: const loader = (await import('@jsdevtools/coverage-istanbul-loader')).default;

Module build failed: Error: Cannot find module 'istanbul-lib-instrument'

Missing peer dependency.

fix

npm install istanbul-lib-instrument --save-dev

Upgrade

Version history

3.0.5latest on npm

Audit

Dependencies

webpackrequiredPeer dependency for loader usage

istanbul-lib-instrumentrequiredCore instrumentation library

Agent activity

13 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/JS-DevTools/coverage-istanbul-loader ↗

packagehttps://www.npmjs.com/package/coverage-istanbul-loader ↗

homepagehttps://jstools.dev/coverage-istanbul-loader ↗