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Unquoted variables in fish's `test`/`[` cause 'Missing argument' errors in completion functions

2026-08-03 (2m ago)7 views

#fish#gopass#shell

I ran into a confusing error every time I tabbed to complete a gopass command in fish:

[: Missing argument at index 3
gopass =
         ^
/opt/homebrew/share/fish/vendor_completions.d/gopass.fish (line 6):
  if [ (count $cmd) -eq 1 -a $cmd[1] = $PROG ]

There were actually two separate bugs stacked on top of each other.

Bug 1: fish doesn't support -a in [

The original gopass fish completion used POSIX's -a operator (logical AND inside test/[):

if [ (count $cmd) -eq 1 -a $cmd[1] = $PROG ]

Fish dropped -a and -o — they were deprecated in POSIX 2008 and fish never implemented them. The fix is to use two separate [ calls with &&:

if [ (count $cmd) -eq 1 ] && [ $cmd[1] = $PROG ]

This is what the upstream gopass repo fixed in February 2026 (PRs #3336 and #3339), but at the time gopass 1.16.1 (the current Homebrew bottle) predates that fix.

Bug 2: unquoted list variable vanishes when empty

Even after applying the upstream fix, the error persisted but changed slightly:

[: Missing argument at index 3
gopass =
         ^
  if [ (count $cmd) -eq 1 ] && [ $cmd[1] = gopass ]

Notice it's gopass = — the left side of the comparison is missing. In fish, if $cmd[1] is an empty list (which happens when commandline -opc returns nothing), an unquoted $cmd[1] expands to nothing at all, so test sees [ = gopass ] and errors.

The fix is to quote it:

if [ (count $cmd) -eq 1 ] && [ "$cmd[1]" = gopass ]

With quotes, an empty list expands to "" rather than disappearing, so test gets [ "" = gopass ] which correctly returns false.

I also replaced $PROG with the literal gopass because $PROG is set at file load time as a global, but by the time the completion function runs, that global is gone from scope.

The actual fix

Since the Homebrew vendor file can't be edited without it being overwritten on upgrade, the fix is to shadow it with a user completion:

curl -s "https://raw.githubusercontent.com/gopasspw/gopass/master/fish.completion" \
  > ~/.config/fish/completions/gopass.fish

Then patch line 6:

# before
if [ (count $cmd) -eq 1 ] && [ $cmd[1] = $PROG ]
 
# after
if [ (count $cmd) -eq 1 ] && [ "$cmd[1]" = gopass ]

Files in ~/.config/fish/completions/ shadow vendor completions from Homebrew, so this wins without touching the Homebrew-managed file. When gopass 1.16.2+ lands in Homebrew with both fixes baked in, you can just delete the override.