Add custom statistics support to coverage calculation

README.md

@@ -407,11 +407,18 @@ browserslist "> 1%, last 2 versions"
 You can get total users coverage for selected browsers by JS API:
 
 ```js
-browserslist.coverage(browserslist('> 1%')) //=> 81.4
+browserslist.coverage(browserslist('> 1%'))
+//=> 81.4
 ```
 
 ```js
-browserslist.coverage(browserslist('> 1% in US'), 'US') //=> 83.1
+browserslist.coverage(browserslist('> 1% in US'), 'US')
+//=> 83.1
+```
+
+```js
+browserslist.coverage(browserslist('> 1% in my stats', { stats }), stats)
+//=> 82.2
 ```
 
 Or by CLI:
@@ -426,6 +433,11 @@ $ browserslist --coverage=US "> 1% in US"
 These browsers account for 83.1% of all users in the US
 ```
 
+```sh
+$ browserslist --coverage "> 1% in my stats" --stats=./browserslist-stats.json
+These browsers account for 83.1% of all users in custom statistics
+```
+
 ## Cache
 
 Browserslist caches the configuration it reads from `package.json` and

cli.js

@@ -1,5 +1,7 @@
 #!/usr/bin/env node
 
+var fs = require('fs')
+
 var browserslist = require('./')
 var pkg = require('./package.json')
 var args = process.argv.slice(2)
@@ -88,12 +90,20 @@ if (isArg('--help') || isArg('-h')) {
       process.stdout.write(browser + '\n')
     })
   } else {
-    var result = browserslist.coverage(browsers, country)
+    var stats
+    if (country) {
+      stats = country
+    } else if (opts.stats) {
+      stats = JSON.parse(fs.readFileSync(opts.stats))
+    }
+    var result = browserslist.coverage(browsers, stats)
     var round = Math.round(result * 100) / 100.0
 
     var end = 'globally'
     if (country && country !== 'global') {
       end = 'in the ' + country.toUpperCase()
+    } else if (opts.stats) {
+      end = 'in custom statistics'
     }
 
     process.stdout.write(

index.js

@@ -276,29 +276,42 @@ browserslist.loadConfig = env.loadConfig
  * Return browsers market coverage.
  *
  * @param {string[]} browsers Browsers names in Can I Use.
- * @param {string} [country="global"] Which country statistics should be used.
+ * @param {string|object} [stats="global"] Which statistics should be used.
+ *                                         Country code or custom statistics.
  *
  * @return {number} Total market coverage for all selected browsers.
  *
  * @example
  * browserslist.coverage(browserslist('> 1% in US'), 'US') //=> 83.1
  */
-browserslist.coverage = function (browsers, country) {
-  if (country && country !== 'global') {
-    if (country.length > 2) {
-      country = country.toLowerCase()
+browserslist.coverage = function (browsers, stats) {
+  var data
+  if (typeof stats === 'undefined') {
+    data = browserslist.usage.global
+  } else if (typeof stats === 'string') {
+    if (stats.length > 2) {
+      stats = stats.toLowerCase()
     } else {
-      country = country.toUpperCase()
+      stats = stats.toUpperCase()
     }
-    env.loadCountry(browserslist.usage, country)
+    env.loadCountry(browserslist.usage, stats)
+    data = browserslist.usage[stats]
   } else {
-    country = 'global'
+    if ('dataByBrowser' in stats) {
+      stats = stats.dataByBrowser
+    }
+    data = { }
+    for (var name in stats) {
+      for (var version in stats[name]) {
+        data[name + ' ' + version] = stats[name][version]
+      }
+    }
   }
 
   return browsers.reduce(function (all, i) {
-    var usage = browserslist.usage[country][i]
+    var usage = data[i]
     if (usage === undefined) {
-      usage = browserslist.usage[country][i.replace(/ [\d.]+$/, ' 0')]
+      usage = data[i.replace(/ [\d.]+$/, ' 0')]
     }
     return all + (usage || 0)
   }, 0)

test/cli.test.js

@@ -132,8 +132,15 @@ it('returns usage from config', () => {
   })
 })
 
-it('support custom stats', () => {
+it('supports custom stats', () => {
   return run('--stats=' + STATS, '> 5% in my stats').then(out => {
     expect(toArray(out)).toEqual(['ie 11', 'ie 10'])
   })
 })
+
+it('supports custom stats in coverage', () => {
+  return run('--coverage', '--stats=' + STATS, '> 5% in my stats').then(out => {
+    expect(out).toEqual(
+      'These browsers account for 15.7% of all users in custom statistics\n')
+  })
+})

test/coverage.test.js

@@ -1,5 +1,12 @@
 var browserslist = require('../')
 
+var custom = {
+  ie: {
+    8: 3,
+    9: 10
+  }
+}
+
 var originUsage = browserslist.usage
 
 beforeEach(() => {
@@ -53,3 +60,8 @@ it('loads continents usage data from Can I Use', () => {
 it('fixes statistics of 0 version', () => {
   expect(browserslist.coverage(['ie 9'], 'RU')).toEqual(2)
 })
+
+it('supports custom statistics', () => {
+  expect(browserslist.coverage(['ie 9'], custom)).toEqual(10)
+  expect(browserslist.coverage(['ie 9'], { dataByBrowser: custom })).toEqual(10)
+})