Infinite WRITE events when watching $TMPDIR on MacOS

[denandz]

Describe the bug

When watching $TMPDIR (/var/folders/[two chars]/[a bunch of chars]/T) on MacOS, and editing a file with VI, fsnotify ends up looping unlimited WRITE events with no file name.

To Reproduce

In one terminal, execute a watch on $TMPDIR using go run ./cmd/fsnotify/ watch $TMPDIR. In a seperate terminal, create a file with vi $TMPDIR/foo, type a single character and save. Saving is not strictly necessary for the loop to trigger. VI writing to the .swp file should trip the condition

doi@sjekira fsnotify % go run ./cmd/fsnotify/ watch $TMPDIR
21:30:54.1816 ready; press ^C to exit
21:30:56.5230   1 CREATE        "/var/folders/hm/d6kgq5lj1p90pskbf495f41c0000gn/T/.foo.swp"
21:30:56.5230   2 CREATE        "/var/folders/hm/d6kgq5lj1p90pskbf495f41c0000gn/T/6588a2e37cfc9"
21:30:57.8665   3 WRITE         "/var/folders/hm/d6kgq5lj1p90pskbf495f41c0000gn/T/.foo.swp"
21:30:57.8667   4 WRITE         ""
21:30:57.8669   5 WRITE         ""
21:30:57.8670   6 WRITE         ""
21:30:57.8671   7 WRITE         ""
21:30:57.8672   8 WRITE         ""
21:30:57.8673   9 WRITE         ""
... yoink ...
21:30:59.3423 89906 WRITE         ""
21:30:59.3424 89907 WRITE         ""
21:30:59.3424 89908 WRITE         ""
21:30:59.3424 89909 WRITE         ""
21:30:59.3424 89910 WRITE         ""

This condition seems to be limited to $TMPDIR with some preliminary testing. The same behaviour does not happen when using vi to edit a file in /private/tmp, for example:

doi@sjekira fsnotify % go run ./cmd/fsnotify/ watch /private/tmp     
21:34:06.7131 ready; press ^C to exit
21:34:17.5683   1 CREATE        "/private/tmp/.foo.swp"
21:34:19.7827   2 WRITE         "/private/tmp/.foo.swp"
21:34:19.7828   3 WRITE         "/private/tmp/.foo.swp"
21:34:19.7870   4 CHMOD         "/private/tmp/foo"
21:34:19.7871   5 WRITE         "/private/tmp/foo"
21:34:19.7898   6 CHMOD         "/private/tmp/foo"
21:34:25.7781   7 WRITE         "/private/tmp/.foo.swp"

Which operating system and version are you using?

ProductName:		macOS
ProductVersion:		13.6.1
BuildVersion:		22G313

M2 Macbook Air

Which fsnotify version are you using?

Main branch commit c94b93b

Did you try the latest main branch?

Yes

[arp242]

I can't reproduce this, using c94b93b:

% print $TMPDIR
/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/

% vim $TMPDIR/x

% fsnotify watch $TMPDIR
14:50:08.3160 ready; press ^C to exit
14:50:19.6281   1 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/com.apple.appstoreagent"
14:50:20.5443   2 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/internal"
14:50:20.6040   3 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/com.apple.ap.promotedcontentd"
14:50:20.7930   4 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/analytics"
14:50:20.8633   5 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/journeys"
14:50:21.3953   6 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/recommendations"
14:50:40.6327   7 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/.x.swp"
14:50:41.2260   8 WRITE         "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/.x.swp"
14:50:42.1262   9 CREATE        "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/x"
14:50:42.1474  10 WRITE         "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/.x.swp"
14:50:46.1560  11 WRITE         "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/.x.swp"
14:50:46.1565  12 WRITE         "/var/folders/01/5qf4m0jn7rz_15kt2fm5p6g40000gn/T/.x.swp"

I used :set updatecount=1 to write the swap file more often, played around a bit – seems to be fine.

This is with pretty much default macOS and whatever it ships with that:

% sw_vers
ProductName:    macOS
ProductVersion: 12.5
BuildVersion:   21G72

And Vim 8.2.5032

---

That is the macOS 12.5 VM I had lying around. I also installed a macOS 13 VM; and using defaults for everything:

% sw_vers
ProductName:            macOS
ProductVersion:         13.6.6
BuildVersion:           22G630

% print $TMPDIR
/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/

% fsnotify watch $TMPDIR
15:43:27.5185 ready; press ^C to exit
15:44:04.3295   1 CREATE        "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.2241   2 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.2242   3 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.2653   4 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.4232   5 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.4246   6 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:09.5105   7 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.1504   8 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.3068   9 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.3068  10 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.4284  11 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.4682  12 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.6210  13 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.6472  14 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.7487  15 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.9113  16 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:11.9125  17 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.0303  18 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.0308  19 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.1684  20 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.1685  21 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.2284  22 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.2296  23 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.2494  24 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.2860  25 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:12.4250  26 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:16.4525  27 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:16.4526  28 WRITE         "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/.x.swp"
15:44:18.9608  29 CREATE        "/var/folders/r8/5kt_pnnd21d2fbhcpgrmhmw00000gn/T/x"

And again, all seems fine. Lots of updates because I set updatecount to 1 again, but seems to work fine. Tried a few times.

Using Vim 9.0.1991

[arp242]

Also there is the test/kqueue.c program, which works identical to fsnotify, but is much more simple. Can you reproduce it with that? Or what does that output?

[arp242]

Also with the main branch you can set the FSNOTIFY_DEBUG=1 environment variable to print more debug info.