fs: add recursive watch for linux

doc/api/fs.md

@@ -4377,10 +4377,6 @@ the returned {fs.FSWatcher}.
 The `fs.watch` API is not 100% consistent across platforms, and is
 unavailable in some situations.
 
-The recursive option is only supported on macOS and Windows.
-An `ERR_FEATURE_UNAVAILABLE_ON_PLATFORM` exception will be thrown
-when the option is used on a platform that does not support it.
-
 On Windows, no events will be emitted if the watched directory is moved or
 renamed. An `EPERM` error is reported when the watched directory is deleted.
 

lib/fs.js

@@ -57,6 +57,7 @@ const {
 
 const pathModule = require('path');
 const { isArrayBufferView } = require('internal/util/types');
+const nonNativeWatcher = require('internal/fs/recursive_watch');
 
 // We need to get the statValues from the binding at the callsite since
 // it's re-initialized after deserialization.
@@ -68,7 +69,6 @@ const {
   codes: {
     ERR_FS_FILE_TOO_LARGE,
     ERR_INVALID_ARG_VALUE,
-    ERR_FEATURE_UNAVAILABLE_ON_PLATFORM,
   },
   AbortError,
   uvErrmapGet,
@@ -163,7 +163,6 @@ let FileWriteStream;
 const isWindows = process.platform === 'win32';
 const isOSX = process.platform === 'darwin';
 
-
 function showTruncateDeprecation() {
   if (truncateWarn) {
     process.emitWarning(
@@ -2297,13 +2296,22 @@ function watch(filename, options, listener) {
 
   if (options.persistent === undefined) options.persistent = true;
   if (options.recursive === undefined) options.recursive = false;
-  if (options.recursive && !(isOSX || isWindows))
-    throw new ERR_FEATURE_UNAVAILABLE_ON_PLATFORM('watch recursively');
-  const watcher = new watchers.FSWatcher();
-  watcher[watchers.kFSWatchStart](filename,
-                                  options.persistent,
-                                  options.recursive,
-                                  options.encoding);
+
+  let watcher;
+
+  // TODO(anonrig): Remove this when/if libuv supports it.
+  // libuv does not support recursive file watch on all platforms, e.g. Linux due to
+  // the limitations of inotify.
+  if (options.recursive && !isOSX && !isWindows) {
+    watcher = new nonNativeWatcher.FSWatcher(options);
+    watcher[watchers.kFSWatchStart](filename);
+  } else {
+    watcher = new watchers.FSWatcher();
+    watcher[watchers.kFSWatchStart](filename,
+                                    options.persistent,
+                                    options.recursive,
+                                    options.encoding);
+  }
 
   if (listener) {
     watcher.addListener('change', listener);

lib/internal/fs/promises.js

@@ -88,7 +88,8 @@ const {
 } = require('internal/util');
 const { EventEmitterMixin } = require('internal/event_target');
 const { StringDecoder } = require('string_decoder');
-const { watch } = require('internal/fs/watchers');
+const { kFSWatchStart, watch } = require('internal/fs/watchers');
+const nonNativeWatcher = require('internal/fs/recursive_watch');
 const { isIterable } = require('internal/streams/utils');
 const assert = require('internal/assert');
 
@@ -120,6 +121,7 @@ const getDirectoryEntriesPromise = promisify(getDirents);
 const validateRmOptionsPromise = promisify(validateRmOptions);
 
 const isWindows = process.platform === 'win32';
+const isOSX = process.platform === 'darwin';
 
 let cpPromises;
 function lazyLoadCpPromises() {
@@ -917,6 +919,26 @@ async function readFile(path, options) {
   return handleFdClose(readFileHandle(fd, options), fd.close);
 }
 
+async function* _watch(filename, options = kEmptyObject) {
+  validateObject(options, 'options');
+
+  if (options.recursive != null) {
+    validateBoolean(options.recursive, 'options.recursive');
+
+    // TODO(anonrig): Remove this when/if libuv supports it.
+    // libuv does not support recursive file watch on all platforms, e.g. Linux due to
+    // the limitations of inotify.
+    if (options.recursive && !isOSX && !isWindows) {
+      const watcher = new nonNativeWatcher.FSWatcher(options);
+      await watcher[kFSWatchStart](filename);
+      yield* watcher;
+      return;
+    }
+  }
+
+  yield* watch(filename, options);
+}
+
 module.exports = {
   exports: {
     access,
@@ -947,7 +969,7 @@ module.exports = {
     writeFile,
     appendFile,
     readFile,
-    watch,
+    watch: !isOSX && !isWindows ? _watch : watch,
     constants,
   },