Fix feature support queries with mobileToDesktop (#767)

* Fix feature support queries with mobileToDesktop

* Update cache type

index.d.ts

@@ -124,7 +124,9 @@ declare namespace browserslist {
 
   let cache: {
     [feature: string]: {
-      [name: string]: 'y' | 'n'
+      [name: string]: {
+        [version: string]: string
+      }
     }
   }
 

index.js

@@ -302,6 +302,13 @@ function filterAndroid(list, versions, context) {
   return list.slice(nEvergreen - 1 - versions)
 }
 
+function isSupported(flags) {
+  return (
+    typeof flags === 'string' &&
+    (flags.indexOf('y') >= 0 || flags.indexOf('a') >= 0)
+  )
+}
+
 function resolve(queries, context) {
   return parse(QUERIES, queries).reduce(function (result, node, index) {
     if (node.not && index === 0) {
@@ -893,13 +900,25 @@ var QUERIES = {
     select: function (context, node) {
       env.loadFeature(browserslist.cache, node.feature)
       var features = browserslist.cache[node.feature]
-      return Object.keys(features).reduce(function (result, version) {
-        var flags = features[version]
-        if (flags.indexOf('y') >= 0 || flags.indexOf('a') >= 0) {
-          result.push(version)
-        }
-        return result
-      }, [])
+      var result = []
+      for (var name in features) {
+        var data = byName(name, context)
+        // Only check desktop when latest released mobile has support
+        var checkDesktop =
+          context.mobileToDesktop &&
+          name in browserslist.desktopNames &&
+          isSupported(features[name][data.released.slice(-1)[0]])
+        data.versions.forEach(function (version) {
+          var flags = features[name][version]
+          if (flags === undefined && checkDesktop) {
+            flags = features[browserslist.desktopNames[name]][version]
+          }
+          if (isSupported(flags)) {
+            result.push(name + ' ' + version)
+          }
+        })
+      }
+      return result
     }
   },
   electron_range: {

node.js

@@ -272,8 +272,9 @@ module.exports = {
     var stats = feature(compressed).stats
     features[name] = {}
     for (var i in stats) {
+      features[name][i] = {}
       for (var j in stats[i]) {
-        features[name][i + ' ' + j] = stats[i][j]
+        features[name][i][j] = stats[i][j]
       }
     }
   },

test/feature.test.js

@@ -4,50 +4,105 @@ let { equal, is, throws } = require('uvu/assert')
 delete require.cache[require.resolve('..')]
 let browserslist = require('..')
 
-let originCache = browserslist.cache
+let originData = { ...browserslist.data }
 
 test.before.each(() => {
-  browserslist.cache = {}
-  browserslist.data.and_chr = {
-    name: 'and_chr',
-    versions: ['81'],
-    released: [],
-    releaseDate: {}
+  browserslist.data = {
+    and_chr: {
+      name: 'and_chr',
+      versions: ['81'],
+      released: ['81'],
+      releaseDate: {}
+    },
+    chrome: {
+      name: 'chrome',
+      versions: ['80', '81', '82'],
+      released: ['80', '81'],
+      releaseDate: {}
+    },
+    ie: {
+      name: 'ie',
+      versions: ['10', '11'],
+      released: ['10', '11'],
+      releaseDate: {}
+    }
   }
 })
 
 test.after.each(() => {
-  browserslist.cache = originCache
+  browserslist.clearCaches()
+  browserslist.data = originData
 })
 
 test('load features from Can I Use', () => {
+  browserslist.data = originData
   is(browserslist('supports objectrtc').length > 0, true)
 })
 
 test('throw an error on wrong feature name from Can I Use', () => {
-  throws(() => browserslist('supports wrong-feature-name'), /Unknown feature name/)
+  throws(
+    () => browserslist('supports wrong-feature-name'),
+    /Unknown feature name/
+  )
 })
 
 test('selects browsers by feature', () => {
-  browserslist.cache = {
-    rtcpeerconnection: {
-      'and_chr 81': 'y',
-      'firefox 2': 'n'
-    }
+  browserslist.cache.rtcpeerconnection = {
+    and_chr: { 81: 'y' },
+    chrome: { 80: 'n', 81: 'y', 82: 'y' },
+    ie: { 10: 'n', 11: 'n' }
   }
 
-  equal(browserslist('supports rtcpeerconnection'), ['and_chr 81'])
+  equal(browserslist('supports rtcpeerconnection'), [
+    'and_chr 81',
+    'chrome 82',
+    'chrome 81'
+  ])
 })
 
 test('selects browsers by feature with dashes in its name', () => {
-  browserslist.cache = {
-    'arrow-functions': {
-      'and_chr 81': 'y',
-      'ie 11': 'n'
-    }
+  browserslist.cache['arrow-functions'] = {
+    and_chr: { 81: 'n' },
+    chrome: { 80: 'n', 81: 'y', 82: 'y' },
+    ie: { 10: 'n', 11: 'y' }
+  }
+
+  equal(browserslist('supports arrow-functions'), [
+    'chrome 82',
+    'chrome 81',
+    'ie 11'
+  ])
+})
+
+test('Selects extra versions with mobile to desktop option', () => {
+  browserslist.cache.filesystem = {
+    and_chr: { 81: 'y' },
+    chrome: { 80: 'y', 81: 'y', 82: 'y' },
+    ie: { 10: 'n', 11: 'n' }
+  }
+
+  equal(browserslist('supports filesystem', { mobileToDesktop: true }), [
+    'and_chr 82',
+    'and_chr 81',
+    'and_chr 80',
+    'chrome 82',
+    'chrome 81',
+    'chrome 80'
+  ])
+})
+
+test('Ignores mobile to desktop if unsupported by latest', () => {
+  browserslist.cache['font-smooth'] = {
+    and_chr: { 81: 'n' },
+    chrome: { 80: 'y', 81: 'y', 82: 'y' },
+    ie: { 10: 'n', 11: 'n' }
   }
 
-  equal(browserslist('supports arrow-functions'), ['and_chr 81'])
+  equal(browserslist('supports font-smooth', { mobileToDesktop: true }), [
+    'chrome 82',
+    'chrome 81',
+    'chrome 80'
+  ])
 })
 
 test.run()