fs: make FSWatcher.start private

lib/fs.js

@@ -1342,10 +1342,10 @@ function watch(filename, options, listener) {
   if (!watchers)
     watchers = require('internal/fs/watchers');
   const watcher = new watchers.FSWatcher();
-  watcher.start(filename,
-                options.persistent,
-                options.recursive,
-                options.encoding);
+  watcher._start(filename,
+                 options.persistent,
+                 options.recursive,
+                 options.encoding);
 
   if (listener) {
     watcher.addListener('change', listener);

lib/internal/fs/watchers.js

@@ -135,18 +135,16 @@ function FSWatcher() {
 Object.setPrototypeOf(FSWatcher.prototype, EventEmitter.prototype);
 Object.setPrototypeOf(FSWatcher, EventEmitter);
 
-
-// FIXME(joyeecheung): this method is not documented.
 // At the moment if filename is undefined, we
-// 1. Throw an Error if it's the first time .start() is called
-// 2. Return silently if .start() has already been called
+// 1. Throw an Error if it's the first time ._start() is called
+// 2. Return silently if ._start() has already been called
 //    on a valid filename and the wrap has been initialized
 // 3. Return silently if the watcher has already been closed
 // This method is a noop if the watcher has already been started.
-FSWatcher.prototype.start = function(filename,
-                                     persistent,
-                                     recursive,
-                                     encoding) {
+FSWatcher.prototype._start = function(filename,
+                                      persistent,
+                                      recursive,
+                                      encoding) {
   if (this._handle === null) {  // closed
     return;
   }

test/parallel/test-fs-watch.js

@@ -58,7 +58,7 @@ for (const testCase of cases) {
   watcher.on('close', common.mustCall(() => {
     watcher.close(); // Closing a closed watcher should be a noop
     // Starting a closed watcher should be a noop
-    watcher.start();
+    watcher._start();
   }));
   watcher.on('change', common.mustCall(function(eventType, argFilename) {
     if (interval) {
@@ -72,15 +72,15 @@ for (const testCase of cases) {
     assert.strictEqual(argFilename, testCase.fileName);
 
     // Starting a started watcher should be a noop
-    watcher.start();
-    watcher.start(pathToWatch);
+    watcher._start();
+    watcher._start(pathToWatch);
 
     watcher.close();
 
     // We document that watchers cannot be used anymore when it's closed,
     // here we turn the methods into noops instead of throwing
     watcher.close(); // Closing a closed watcher should be a noop
-    watcher.start();  // Starting a closed watcher should be a noop
+    watcher._start();  // Starting a closed watcher should be a noop
   }));
 
   // Long content so it's actually flushed. toUpperCase so there's real change.