Feature request: Listen could *really ignore* ignored directories (optimization)

[e2]

TL; DR - UPDATE: this feature doesn't make sense due to technical limitations of the adapters.

Listen currently watches every file in a watched directory and applies the filter after receiving system events.

On optimized backends, this causes lots of unnecessary calls through Ruby upon every file change.

(e.g. changes in db/test.sqlite trigger changes through Listen)

How to implement (minimal work)

1. disable recursion on all optimized adapters: windows.rb (see wdm), darwin.rb (see: rb-fsevent) [note, "disabling" here means ignoring reported subdirs], linux.rb (see: rb-inotify))
2. get listen working again by implementing the recursion in Ruby in the base adapter (rb-inotify has a great Ruby implementation of recursion)
3. get the adapter to turn a watched directory into an array of directories to watch non-recursively here
4. Finally, translate physical paths backs into symlink paths (if they exist) here: https://github.com/guard/listen/blob/master/lib/listen/adapter/base.rb#L47

[e2]

@thibaudgg - is it possible to turn off recursion in rb-fsevent? (and I'm wondering if I haven't already asked this before).

The workaround is to simply ignore events on subdirectories, but in this case means potentially giving each rb-fsevent instance a full list of all subdirectories containing each other, e.g. if I have:

foo/bar/baz/bam/, then rb-fsevent will get: foo, foo/bar, foo/bar/baz, foo/bar/baz/bam.

Would that affect rb-fsevent performance for large projects on the rb-fsevent side? Would listen get multiple events (4 in this case) if something is modified in foo/bar/baz/bam?

[thibaudgg]

@e2 sadly not, I don't think this is possible with the actual implementation of rb-fsevent.

[e2]

@thibaudgg - thanks! You saved me time digging into this - which I appreciate a lot!