Update core 8.3.0

web/core/scripts/js/babel-es6-watch.js

@@ -0,0 +1,67 @@
+/**
+ * @file
+ *
+ * Watch changes to *.es6.js files and compile them to ES5 during development.
+ *
+ * @internal This file is part of the core javascript build process and is only
+ * meant to be used in that context.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const babel = require('babel-core');
+const chokidar = require('chokidar');
+
+// Logging human-readable timestamp.
+const log = function log(message) {
+  // eslint-disable-next-line no-console
+  console.log(`[${new Date().toTimeString().slice(0, 8)}] ${message}`);
+};
+
+function addSourceMappingUrl(code, loc) {
+  return `${code}\n\n//# sourceMappingURL=${path.basename(loc)}`;
+}
+
+const fileMatch = './**/*.es6.js';
+const watcher = chokidar.watch(fileMatch, {
+  ignoreInitial: true,
+  ignored: 'node_modules/**'
+});
+
+const changedOrAdded = (filePath) => {
+  babel.transformFile(filePath, {
+    sourceMaps: true,
+    comments: false
+  }, (err, result) => {
+    const fileName = filePath.slice(0, -7);
+    // we've requested for a sourcemap to be written to disk
+    const mapLoc = `${fileName}.js.map`;
+
+    fs.writeFileSync(mapLoc, JSON.stringify(result.map));
+    fs.writeFileSync(`${fileName}.js`, addSourceMappingUrl(result.code, mapLoc));
+
+    log(`'${filePath}' has been changed.`);
+  });
+};
+
+const unlinkHandler = (err) => {
+  if (err) {
+    log(err);
+  }
+};
+
+watcher
+  .on('add', filePath => changedOrAdded(filePath))
+  .on('change', filePath => changedOrAdded(filePath))
+  .on('unlink', (filePath) => {
+    const fileName = filePath.slice(0, -7);
+    fs.stat(`${fileName}.js`, () => {
+      fs.unlink(`${fileName}.js`, unlinkHandler);
+    });
+    fs.stat(`${fileName}.js.map`, () => {
+      fs.unlink(`${fileName}.js.map`, unlinkHandler);
+    });
+  })
+  .on('ready', () => log(`Watching '${fileMatch}' for changes.`));