Upgrade to babel 7

In this diff I moved build to babel 7, removed unused packages and made
babel helpers importable from runtime. This allows to reuse these
helpers across many packages and save a few kilobytes in user bundle.

babel.config.js

@@ -0,0 +1,7 @@
+module.exports = {
+  presets: [['@babel/env', { loose: true }], '@babel/flow'],
+  plugins: [
+    ['@babel/proposal-class-properties', { loose: true }],
+    'annotate-pure-calls',
+  ],
+};

package.json

@@ -1,10 +1,8 @@
 {
   "name": "react-window",
   "version": "1.1.1",
-  "description":
-    "React components for efficiently rendering large, scrollable lists and tabular data",
-  "author":
-    "Brian Vaughn <[email protected]> (https://github.com/bvaughn/)",
+  "description": "React components for efficiently rendering large, scrollable lists and tabular data",
+  "author": "Brian Vaughn <[email protected]> (https://github.com/bvaughn/)",
   "contributors": [
     "Brian Vaughn <[email protected]> (https://github.com/bvaughn/)"
   ],
@@ -36,7 +34,9 @@
   ],
   "main": "dist/index.cjs.js",
   "module": "dist/index.esm.js",
-  "files": ["dist"],
+  "files": [
+    "dist"
+  ],
   "scripts": {
     "precommit": "lint-staged",
     "prettier": "prettier --write '**/*.{js,json,css}'",
@@ -52,24 +52,29 @@
     "website:run": "cd website && yarn start"
   },
   "lint-staged": {
-    "{website,src}/**/*.{js,json,css}": ["prettier --write", "git add"],
+    "{website,src}/**/*.{js,json,css}": [
+      "prettier --write",
+      "git add"
+    ],
     "**/*.js": "eslint --max-warnings 0"
   },
   "dependencies": {
+    "@babel/runtime": "^7.0.0",
     "memoize-one": "^3.1.1"
   },
   "peerDependencies": {
     "react": "^15.0.0 || ^16.0.0",
     "react-dom": "^15.0.0 || ^16.0.0"
   },
   "devDependencies": {
-    "babel-core": "^6.26.0",
-    "babel-eslint": "^8.2.1",
+    "@babel/core": "^7.0.0",
+    "@babel/plugin-proposal-class-properties": "^7.0.0",
+    "@babel/plugin-transform-runtime": "^7.0.0",
+    "@babel/preset-env": "^7.0.0",
+    "@babel/preset-flow": "^7.0.0",
+    "babel-core": "^7.0.0-bridge.0",
+    "babel-eslint": "^9.0.0",
     "babel-plugin-annotate-pure-calls": "^0.3.0",
-    "babel-plugin-external-helpers": "^6.22.0",
-    "babel-preset-env": "^1.6.0",
-    "babel-preset-react": "^6.24.1",
-    "babel-preset-stage-0": "^6.24.1",
     "cross-env": "^5.1.4",
     "del-cli": "^1.1.0",
     "eslint": "^4.19.1",
@@ -92,12 +97,9 @@
     "react-dom": "^16.4.0",
     "react-scripts": "^1.1.1",
     "react-test-renderer": "^16.4.0",
-    "rollup": "^0.59.3",
-    "rollup-plugin-babel": "^3.0.3",
+    "rollup": "^0.65.0",
+    "rollup-plugin-babel": "^4.0.2",
     "rollup-plugin-commonjs": "^8.2.1",
-    "rollup-plugin-node-resolve": "^3.0.2",
-    "rollup-plugin-peer-deps-external": "^2.2.0",
-    "rollup-plugin-postcss": "^1.1.0",
-    "rollup-plugin-url": "^1.3.0"
+    "rollup-plugin-node-resolve": "^3.0.2"
   }
 }

rollup.config.js

@@ -1,34 +1,44 @@
 import babel from 'rollup-plugin-babel';
 import commonjs from 'rollup-plugin-commonjs';
-import external from 'rollup-plugin-peer-deps-external';
-import postcss from 'rollup-plugin-postcss';
-import resolve from 'rollup-plugin-node-resolve';
-import url from 'rollup-plugin-url';
-
+import nodeResolve from 'rollup-plugin-node-resolve';
 import pkg from './package.json';
 
-export default {
-  input: 'src/index.js',
-  output: [
-    {
+const input = './src/index.js';
+
+const external = id => !id.startsWith('.') && !id.startsWith('/');
+
+export default [
+  {
+    input,
+    output: {
       file: pkg.main,
       format: 'cjs',
     },
-    {
+    external,
+    plugins: [
+      babel({
+        runtimeHelpers: true,
+        plugins: ['@babel/transform-runtime'],
+      }),
+      nodeResolve(),
+      commonjs(),
+    ],
+  },
+
+  {
+    input,
+    output: {
       file: pkg.module,
       format: 'esm',
     },
-  ],
-  plugins: [
-    external({ includeDependencies: true }),
-    postcss({
-      modules: true,
-    }),
-    url(),
-    babel({
-      exclude: 'node_modules/**',
-    }),
-    resolve(),
-    commonjs(),
-  ],
-};
+    external,
+    plugins: [
+      babel({
+        runtimeHelpers: true,
+        plugins: [['@babel/transform-runtime', { useESModules: true }]],
+      }),
+      nodeResolve(),
+      commonjs(),
+    ],
+  },
+];