Use external Electron to Chromium library

package.json

@@ -46,7 +46,8 @@
     "babel-plugin-transform-exponentiation-operator": "^6.8.0",
     "babel-plugin-transform-regenerator": "^6.6.0",
     "browserslist": "^1.4.0",
-    "invariant": "^2.2.2"
+    "invariant": "^2.2.2",
+    "electron-to-chromium": "^1.1.0"
   },
   "devDependencies": {
     "babel-cli": "^6.11.4",

src/index.js

@@ -1,8 +1,7 @@
 import browserslist from "browserslist";
-
 import builtInsList from "../data/built-ins.json";
 import defaultInclude from "./default-includes";
-import electronToChromium from "../data/electron-to-chromium";
+import { electronToChromium } from "electron-to-chromium";
 import moduleTransformations from "./module-transformations";
 import normalizeOptions from "./normalize-options.js";
 import pluginList from "../data/plugins.json";
@@ -82,26 +81,6 @@ export const getCurrentNodeVersion = () => {
   return parseFloat(process.versions.node);
 };
 
-export const electronVersionToChromeVersion = (semverVer) => {
-  semverVer = String(semverVer);
-
-  if (semverVer === "1") {
-    semverVer = "1.0";
-  }
-
-  const m = semverVer.match(/^(\d+\.\d+)/);
-  if (!m) {
-    throw new Error("Electron version must be a semver version");
-  }
-
-  const result = electronToChromium[m[1]];
-  if (!result) {
-    throw new Error(`Electron version ${m[1]} is either too old or too new`);
-  }
-
-  return result;
-};
-
 const _extends = Object.assign || function (target) {
   for (let i = 1; i < arguments.length; i++) {
     const source = arguments[i];
@@ -124,7 +103,18 @@ export const getTargets = (targets = {}) => {
 
   // Rewrite Electron versions to their Chrome equivalents
   if (targetOps.electron) {
-    targetOps.chrome = electronVersionToChromeVersion(targetOps.electron);
+    const electronChromeVersion = parseInt(electronToChromium(targetOps.electron), 10);
+
+    if (!electronChromeVersion) {
+      throw new Error(`Electron version ${targetOps.electron} is either too old or too new`);
+    }
+
+    if (targetOps.chrome) {
+      targetOps.chrome = Math.min(targetOps.chrome, electronChromeVersion);
+    } else {
+      targetOps.chrome = electronChromeVersion;
+    }
+
     delete targetOps.electron;
   }
 

test/fixtures/preset-options/electron/expected.js

@@ -1,8 +1,11 @@
+import "core-js/modules/es7.object.values";
+import "core-js/modules/es7.object.entries";
+import "core-js/modules/es7.object.get-own-property-descriptors";
 import "core-js/modules/es7.string.pad-start";
 import "core-js/modules/es7.string.pad-end";
 import "core-js/modules/web.timers";
 import "core-js/modules/web.immediate";
 import "core-js/modules/web.dom.iterable";
 
 
-a ** b;
+a ** b;

test/fixtures/preset-options/electron/options.json

@@ -2,7 +2,7 @@
   "presets": [
     ["../../../../lib", {
       "targets": {
-        "electron": 1.5
+        "electron": 1.4
       },
       "modules": false,
       "useBuiltIns": true

test/index.spec.js

@@ -2,7 +2,7 @@
 
 const babelPresetEnv = require("../lib/index.js");
 const assert = require("assert");
-const electronToChromiumData = require("../data/electron-to-chromium");
+const { versions: electronToChromiumData } = require("electron-to-chromium");
 
 describe("babel-preset-env", () => {
   describe("getTargets", () => {
@@ -26,18 +26,37 @@ describe("babel-preset-env", () => {
       assert.deepEqual(babelPresetEnv.getTargets({
         electron: "1.0"
       }), {
-        chrome: 50
+        chrome: 49
       });
     });
 
     it("should work with a number", function() {
       assert.deepEqual(babelPresetEnv.getTargets({
         electron: 1.0
+      }), {
+        chrome: 49
+      });
+    });
+
+
+    it("should preserve lower Chrome number if Electron version is more recent", function() {
+      assert.deepEqual(babelPresetEnv.getTargets({
+        electron: 1.4,
+        chrome: 50
       }), {
         chrome: 50
       });
     });
 
+    it("should overwrite Chrome number if Electron version is older", function() {
+      assert.deepEqual(babelPresetEnv.getTargets({
+        electron: 1.0,
+        chrome: 50
+      }), {
+        chrome: 49
+      });
+    });
+
     Object.keys(electronToChromiumData).forEach((electronVersion) => {
       it(`"should work for Electron: ${electronVersion}`, function() {
         assert.deepEqual(babelPresetEnv.getTargets({