feat: support source maps

lib/nuke.js

@@ -1,9 +1,21 @@
+const _ = require('lodash')
 const postcss = require('postcss')
 const plugin = require('./plugin')
 
-function nuke(sources, css, opts) {
+function toPostcssOpts(opts) {
+  if (opts.sourceMap) {
+    const mainOpts = _.pick(opts.sourceMap, ['from', 'to'])
+    const map = _.pick(opts.sourceMap, ['inline'])
+    return Object.assign(mainOpts, {map})
+  }
+}
+
+function nuke(sources, css, opts = {}) {
   const processor = postcss([plugin(sources, opts)])
-  return processor.process(css).css
+  const processed = processor.process(css, toPostcssOpts(opts))
+  return opts.sourceMap ?
+    {css: processed.css, map: JSON.parse(processed.map.toString())} :
+    processed.css
 }
 
 module.exports = nuke

package.json

@@ -62,6 +62,7 @@
     "semantic-release": "^6.3.2",
     "sinon": "^1.17.7",
     "sinon-chai": "^2.8.0",
+    "source-map": "^0.5.6",
     "xo": "patrickhulce/xo#master"
   }
 }

test/fixtures/content.css

@@ -22,6 +22,6 @@ html .something > foobar[something=x] #xb {
   }
 }
 
-.something {
+.unused, .something {
   color: white;
 }

test/nuke.test.js

@@ -1,5 +1,6 @@
 const fs = require('fs')
 const path = require('path')
+const SourceMapConsumer = require('source-map').SourceMapConsumer
 const nukecss = require('../lib/nuke')
 
 describe('nuke.js', () => {
@@ -120,4 +121,39 @@ describe('nuke.js', () => {
       expect(result).to.contain('.totally-unused')
     })
   })
+
+  context('when sourceMaps are enabled', () => {
+    const filePath = 'file://' + path.join(__dirname, '/fixtures/content.html')
+    const cssContent = fs.readFileSync(path.join(__dirname, '/fixtures/content.css'), 'utf8')
+    const sourceMap = {from: 'content.css', to: 'content.css', inline: false}
+    const result = nukecss(filePath, cssContent, {sourceMap})
+
+    function findLineAndColumn(css, string) {
+      const lines = css.split('\n')
+      const line = lines.findIndex(l => l.includes(string)) + 1
+      if (line === -1) {
+        throw new Error(`could not find string ${string}`)
+      }
+
+      const column = lines[line - 1].indexOf(string) + 1
+      return {line, column}
+    }
+
+    it('should return an object', () => {
+      expect(result).to.be.an('object')
+      expect(result).to.have.property('css')
+      expect(result).to.have.property('map')
+    })
+
+    it('should produce a valid sourcemap', () => {
+      const string = '.something {'
+      const realLocation = findLineAndColumn(cssContent, string)
+      const location = findLineAndColumn(result.css, string)
+      const consumer = new SourceMapConsumer(result.map)
+
+      const sourceMapPosition = consumer.originalPositionFor(location)
+      expect(sourceMapPosition.line).to.be.greaterThan(location.line)
+      expect(sourceMapPosition.line).to.equal(realLocation.line)
+    })
+  })
 })