cmd/govim: use of fsnotify holds too many open files on macOS

[myitcv]

What version of Vim/Gvim are you using?

Vim/Gvim version

$ vim --version
VIM - Vi IMproved 8.1 (2018 May 18, compiled Jul  5 2019 16:04:22)
macOS version
Included patches: 1-1518
Compiled by pauljolly@Pauls-MacBook-Pro.local
Huge version without GUI.  Features included (+) or not (-):
+acl               -farsi             -mouse_sysmouse    -tag_any_white
+arabic            +file_in_path      +mouse_urxvt       -tcl
+autocmd           +find_in_path      +mouse_xterm       +termguicolors
+autochdir         +float             +multi_byte        +terminal
-autoservername    +folding           +multi_lang        +terminfo
-balloon_eval      -footer            -mzscheme          +termresponse
+balloon_eval_term +fork()            +netbeans_intg     +textobjects
-browse            -gettext           +num64             +textprop
++builtin_terms    -hangul_input      +packages          +timers
+byte_offset       +iconv             +path_extra        +title
+channel           +insert_expand     -perl              -toolbar
+cindent           +job               +persistent_undo   +user_commands
-clientserver      +jumplist          +postscript        +vartabs
+clipboard         +keymap            +printer           +vertsplit
+cmdline_compl     +lambda            +profile           +virtualedit
+cmdline_hist      +langmap           -python            +visual
+cmdline_info      +libcall           -python3           +visualextra
+comments          +linebreak         +quickfix          +viminfo
+conceal           +lispindent        +reltime           +vreplace
+cryptv            +listcmds          +rightleft         +wildignore
-cscope            +localmap          -ruby              +wildmenu
+cursorbind        -lua               +scrollbind        +windows
+cursorshape       +menu              +signs             +writebackup
+dialog_con        +mksession         +smartindent       -X11
+diff              +modify_fname      -sound             -xfontset
+digraphs          +mouse             +spell             -xim
-dnd               -mouseshape        +startuptime       -xpm
-ebcdic            +mouse_dec         +statusline        -xsmp
+emacs_tags        -mouse_gpm         -sun_workshop      -xterm_clipboard
+eval              -mouse_jsbterm     +syntax            -xterm_save
+ex_extra          +mouse_netterm     +tag_binary        
+extra_search      +mouse_sgr         -tag_old_static    
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
 2nd user vimrc file: "~/.vim/vimrc"
      user exrc file: "$HOME/.exrc"
       defaults file: "$VIMRUNTIME/defaults.vim"
  fall-back for $VIM: "/Users/pauljolly/usr/vim/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H   -DMACOS_X -DMACOS_X_DARWIN  -g -O2 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=1       
Linking: gcc   -L/usr/local/lib -o vim        -lm -lncurses  -liconv -framework AppKit           

What version of Go are you using (go version)?

$ go version
go version go1.12.6 darwin/amd64

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/pauljolly/Library/Caches/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/pauljolly/gostuff"
GOPROXY=""
GORACE=""
GOROOT="/usr/local/Cellar/go/1.12.6/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.12.6/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/dr/dr09wv9n7l9_j_z635q0p7rr0000gp/T/go-build502338012=/tmp/go-build -gno-record-gcc-switches -fno-common"

What version/commit of govim are you using?

b6bbbae

What is the output of :messages in Vim?

n/a

Do the Vim channel, govim or gopls log files show anything interesting?

n/a

How did you install govim?

n/a

What did you do?

Open govim.go in a clone of this repo

What did you expect to see?

A small number of open files reported by lsof for the govim process

What did you see instead?

~255 files open, i.e. all of the files in the govim repo. These files are open because fsnotify uses a slightly old mechanism for watching files on macOS: fsnotify/fsnotify#11

[myitcv]

cc @leitzler

[myitcv]

One option appears to be using https://github.com/fsnotify/fsevents

[leitzler]

I'll try out fsevents just because this bites me a little bit too often (and I would just forget about this issue if I changed my default ulimit) :)