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131 lines
4.5 KiB
Markdown
131 lines
4.5 KiB
Markdown
# babel-plugin-istanbul
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[](https://greenkeeper.io/)
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[](https://travis-ci.org/istanbuljs/babel-plugin-istanbul)
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[](https://coveralls.io/github/istanbuljs/babel-plugin-istanbul?branch=master)
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[](https://conventionalcommits.org)
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[](http://devtoolscommunity.herokuapp.com)
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_Having problems? want to contribute? join our [community slack](http://devtoolscommunity.herokuapp.com)_.
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A Babel plugin that instruments your code with Istanbul coverage.
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It can instantly be used with [karma-coverage](https://github.com/karma-runner/karma-coverage) and mocha on Node.js (through [nyc](https://github.com/bcoe/nyc)).
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__Note:__ This plugin does not generate any report or save any data to any file;
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it only adds instrumenting code to your JavaScript source code.
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To integrate with testing tools, please see the [Integrations](#integrations) section.
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## Usage
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Install it:
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```
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npm install --save-dev babel-plugin-istanbul
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```
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Add it to `.babelrc` in test mode:
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```js
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{
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"env": {
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"test": {
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"plugins": [ "istanbul" ]
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}
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}
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}
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```
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Optionally, use [cross-env](https://www.npmjs.com/package/cross-env) to set
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`NODE_ENV=test`:
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```json
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{
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"scripts": {
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"test": "cross-env NODE_ENV=test nyc --reporter=lcov --reporter=text mocha test/*.js"
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}
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}
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```
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## Integrations
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### karma
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It _just works_ with Karma. First, make sure that the code is already transpiled by Babel (either using `karma-babel-preprocessor`, `karma-webpack`, or `karma-browserify`). Then, simply set up [karma-coverage](https://github.com/karma-runner/karma-coverage) according to the docs, but __don’t add the `coverage` preprocessor.__ This plugin has already instrumented your code, and Karma should pick it up automatically.
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It has been tested with [bemusic/bemuse](https://codecov.io/github/bemusic/bemuse) project, which contains ~2400 statements.
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### mocha on node.js (through nyc)
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Configure Mocha to transpile JavaScript code using Babel, then you can run your tests with [`nyc`](https://github.com/bcoe/nyc), which will collect all the coverage report.
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babel-plugin-istanbul respects the `include`/`exclude` configuration options from nyc,
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but you also need to __configure NYC not to instrument your code__ by adding these settings in your `package.json`:
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```js
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"nyc": {
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"sourceMap": false,
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"instrument": false
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},
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```
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## Ignoring files
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You don't want to cover your test files as this will skew your coverage results. You can configure this by providing plugin options matching nyc's [`exclude`/`include` rules](https://github.com/bcoe/nyc#excluding-files):
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```json
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{
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"env": {
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"test": {
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"plugins": [
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["istanbul", {
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"exclude": [
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"**/*.spec.js"
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]
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}]
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]
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}
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}
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}
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```
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If you don't provide options in your Babel config, the plugin will look for `exclude`/`include` config under an `"nyc"` key in `package.json`.
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You can also use [istanbul's ignore hints](https://github.com/gotwarlost/istanbul/blob/master/ignoring-code-for-coverage.md#ignoring-code-for-coverage-purposes) to specify specific lines of code to skip instrumenting.
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## Source Maps
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By default, this plugin will pick up inline source maps and attach them to the instrumented code such that code coverage can be remapped back to the original source, even for multi-step build processes. This can be memory intensive. Set `useInlineSourceMaps` to prevent this behavior.
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```json
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{
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"env": {
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"test": {
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"plugins": [
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["istanbul", {
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"useInlineSourceMaps": false
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}]
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]
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}
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}
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}
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```
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If you're instrumenting code programatically, you can pass a source map explicitly.
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```js
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import babelPluginIstanbul from 'babel-plugin-istanbul';
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function instrument(sourceCode, sourceMap, fileName) {
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return babel.transform(sourceCode, {
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filename,
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plugins: [
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[babelPluginIstanbul, {
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inputSourceMap: sourceMap
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}]
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]
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})
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}
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```
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## Credit where credit is due
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The approach used in `babel-plugin-istanbul` was inspired by [Thai Pangsakulyanont](https://github.com/dtinth)'s original library [`babel-plugin-__coverage__`](https://github.com/dtinth/babel-plugin-__coverage__).
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