fs: improve errors in watchFile and unwatchFile

- Check if the watcher is active in JS land before
  invoking the binding, act as a noop if the state of
  the watcher does not match the expectation. This
  avoids firing 'stop' when the watcher is already
  stopped.
- Update comments, validate more arguments and
  the type of the handle.
- Handle the errors from uv_fs_poll_start
- Create an `IsActive` helper method on StatWatcher

PR-URL: https://github.com/nodejs/node/pull/19345
Refs: https://github.com/nodejs/node/pull/19089
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/test/sequential/test-fs-watch.js b/test/sequential/test-fs-watch.js
index 91d750acd0..3c8ae0eba7 100644
--- a/test/sequential/test-fs-watch.js
+++ b/test/sequential/test-fs-watch.js
@@ -122,13 +122,20 @@ tmpdir.refresh();
     code: 'ERR_ASSERTION'
   });
   oldhandle.close(); // clean up
+}
 
-  assert.throws(function() {
-    const w = fs.watchFile(__filename, { persistent: false },
+{
+  let oldhandle;
+  assert.throws(() => {
+    const w = fs.watchFile(__filename,
+                           { persistent: false },
                            common.mustNotCall());
     oldhandle = w._handle;
     w._handle = { stop: w._handle.stop };
     w.stop();
-  }, /^TypeError: Illegal invocation$/);
+  }, {
+    message: 'handle must be a StatWatcher',
+    code: 'ERR_ASSERTION'
+  });
   oldhandle.stop(); // clean up
 }