go.exp/fsnotify: Watching directories themselves.

[gopherbot]

by larzconwell:

Currently when you watch a directory it watches all the files in the directory, it think
it'd be nice if it were possible to watch just the directory.

Here's the use case I'm doing. I am watching all the paths in a directory tree but a
user can give a set of files/directories to skip watching.

It's kind of difficult because if you RemoveWatch one of the files and it's directory
still needs to be watched you'll still get events for it.

[ianlancetaylor]

Comment 1:

Labels changed: added repo-exp, release-none.

[nathany]

Comment 2:

Thanks for the feedback. Right now kqueue (BSD/OSX) are doing a bunch of extra work to
watch the files in a directory... it actually only provides what you are asking for
here. inotify (Linux) offers both options. FSEvents (OSX) is oriented around watching
everything in a directory, it may not provide this option. I don't recall for Windows.
We're still not sure how we'll sort out all these differences.
This is further complicated by text editors often using "atomic saves" by creating a new
file and then renaming it overtop of the old one. Even with kqueue, this results in an
event saying "something has changed in this directory", whereas a simple touch would be
ignored without a file-level watch.
So I'm not sure what the right answer is. It looks like we can't really rely upon
RemoveWatch to be used this way. The easiest solution for now is probably to filter out
the exclusions yourself as you receive events over the channel.

[gopherbot]

Comment 3 by larzconwell:

Yeah filtering events is what we're doing now, it's working pretty well. 
Just thought it would be a nice feature to add, but if fsevents is being considered and
it's not possible it's not really a big deal.

[gopherbot]

Comment 4 by elia@schito.me:

I'll add a couple of notes:
- watching huge directories results in "too many open files"
- Listen (https://github.com/guard/listen#readme) tackles the same problem and has been
there for a while, if there's a common ground between the various implementation I bet
they got it.
- maybe it's worth exposing the single adapters for ppl to dig deeper while keeping a
surface API for the stuff that's common between them
For the record my use-case regards watching some folders and know if anything changed
inside them, but not caring for the single files.

[nathany]

Comment 5:

For more thoughts on this issue, please see:
https://github.com/go-fsnotify/fsnotify/issues/16

[rsc]

fsnotify has been removed from exp