1 files changed, 81 insertions, 0 deletions
diff --git a/devtools/client/shared/file-watcher-worker.js b/devtools/client/shared/file-watcher-worker.js
new file mode 100644
index 000000000..c9edd6127
--- /dev/null
+++ b/devtools/client/shared/file-watcher-worker.js
@@ -0,0 +1,81 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+/* eslint-env worker */
+/* global OS */
+importScripts("resource://gre/modules/osfile.jsm");
+
+const modifiedTimes = new Map();
+
+function gatherFiles(path, fileRegex) {
+  let files = [];
+  const iterator = new OS.File.DirectoryIterator(path);
+
+  try {
+    for (let child in iterator) {
+      // Don't descend into test directories. Saves us some time and
+      // there's no reason to.
+      if (child.isDir && !child.path.endsWith("/test")) {
+        files = files.concat(gatherFiles(child.path, fileRegex));
+      } else if (child.path.match(fileRegex)) {
+        let info;
+        try {
+          info = OS.File.stat(child.path);
+        } catch (e) {
+          // Just ignore it.
+          continue;
+        }
+
+        files.push(child.path);
+        modifiedTimes.set(child.path, info.lastModificationDate.getTime());
+      }
+    }
+  } finally {
+    iterator.close();
+  }
+
+  return files;
+}
+
+function scanFiles(files, onChangedFile) {
+  files.forEach(file => {
+    let info;
+    try {
+      info = OS.File.stat(file);
+    } catch (e) {
+      // Just ignore it. It was probably deleted.
+      return;
+    }
+
+    const lastTime = modifiedTimes.get(file);
+
+    if (info.lastModificationDate.getTime() > lastTime) {
+      modifiedTimes.set(file, info.lastModificationDate.getTime());
+      onChangedFile(file);
+    }
+  });
+}
+
+onmessage = function (event) {
+  const { path, fileRegex } = event.data;
+
+  const info = OS.File.stat(path);
+  if (!info.isDir) {
+    throw new Error("Watcher expects a directory as root path");
+  }
+
+  // We get a list of all the files upfront, which means we don't
+  // support adding new files. But you need to rebuild Firefox when
+  // adding a new file anyway.
+  const files = gatherFiles(path, fileRegex || /.*/);
+
+  // Every second, scan for file changes by stat-ing each of them and
+  // comparing modification time.
+  setInterval(() => {
+    scanFiles(files, changedFile => {
+      postMessage({ path: changedFile });
+    });
+  }, 1000);
+};