Do not bundle polyfills with knex

UPGRADING.md

@@ -4,7 +4,8 @@
 
 * MSSQL: DB versions older than 2008 are no longer supported, make sure to update your DB;
 * PostgreSQL|MySQL: it is recommended to use options object for `table.datetime` and `table.timestamp` methods instead of argument options. See documentation for these methods for more details; 
-* Node 6: There are known issues with duplicate event listeners when using knex.js with Node 6 (resulting in MaxListenersExceededWarning under certain use-cases (such as reusing single knex instance to run migrations or seeds multiple times)). Please upgrade to Node 8+ as soon as possible (knex 0.17.0 will be dropping Node 6 support altogether).
+* Node 6: There are known issues with duplicate event listeners when using knex.js with Node.js 6 (resulting in MaxListenersExceededWarning under certain use-cases (such as reusing single knex instance to run migrations or seeds multiple times)). Please upgrade to Node.js 8+ as soon as possible (knex 0.17.0 will be dropping Node.js 6 support altogether);
+* Node 6: Please add '@babel/polyfill' production dependency to the project when using Node.js 6 (it will be loaded by knex automatically).
 
 ### Upgrading to version 0.15.0+
 

knex.js

@@ -9,13 +9,19 @@ const { isNode6 } = require('./lib/util/version-helper');
 
 // Should be safe to remove after support for Node.js 6 is dropped
 if (isNode6()) {
-  const oldPromise = global.Promise;
+  try {
+    const oldPromise = global.Promise;
 
-  require('@babel/polyfill');
+    require('@babel/polyfill');
 
-  // Preserve any Promise overrides set globally prior to importing knex
-  if (oldPromise) {
-    global.Promise = oldPromise;
+    // Preserve any Promise overrides set globally prior to importing knex
+    if (oldPromise) {
+      global.Promise = oldPromise;
+    }
+  } catch (e) {
+    throw new Error(
+      `You are using Node.js 6. Please consider upgrading to Node.js 8+ or add '@babel/polyfill' dependency to the project (knex will automatically load it).`
+    );
   }
 }
 

package.json

@@ -8,7 +8,6 @@
     "node": ">=6"
   },
   "dependencies": {
-    "@babel/polyfill": "^7.2.5",
     "@types/bluebird": "^3.5.25",
     "bluebird": "^3.5.3",
     "colorette": "1.0.7",
@@ -35,6 +34,7 @@
   "devDependencies": {
     "@babel/cli": "^7.2.3",
     "@babel/core": "^7.2.2",
+    "@babel/polyfill": "^7.2.5",
     "@babel/preset-env": "^7.3.1",
     "@types/node": "*",
     "JSONStream": "^1.3.5",

src/migrate/sources/fs-migrations.js

@@ -3,7 +3,8 @@ import path from 'path';
 import Promise from 'bluebird';
 import { sortBy, filter } from 'lodash';
 
-const readDirAsync = (path) => Promise.promisify(fs.readdir, { context: fs })(path);
+const readDirAsync = (path) =>
+  Promise.promisify(fs.readdir, { context: fs })(path);
 
 export const DEFAULT_LOAD_EXTENSIONS = Object.freeze([
   '.co',