Re: Behaviour of test -v with assoc array and quote character in key

[Chet Ramey]

On 2/14/21 6:27 PM, Daniel Gröber wrote:
> Hi list,
>
> I've found what I belive to be a bug in how `test -v` expands the key in an
> associative array. The following minimal test case demonstrates the
> problem:
>
>      declare -A array
>      
>      mytest () {
>              array["$1"]=123
>              test -v array["$1"]
>              printf 'test -v array[%s]; $?=%s\n' "$1" "$?"
>      }
>      
>      mytest 'a' # prints: test -v array[a]; $?=0
>      mytest '"' # prints: test -v array["]; $?=1
>      echo "keys: ${!array[*]}" # prints: keys: " a
>
> With a regular alphanumeric key `test -v` will return zero, indicating the
> array element exists. However if we specify a variable that expands to
> something containing the double quote character the test doesn't succeeed
> indicating the key doesn't exist though it does as we can observe by the
> expansion of ${!array[*]}.
>
> Do you think this intended behaviour or a real bug?

`test' is always going to be problematic here because, as a shell builtin,
its arguments undergo a round of word expansions before it's invoked. It's
difficult to reliably detect the closing bracket in an array subscript as a
result, even if the array subscript expansion didn't perform any expansions
on its own. (Consider what would happen if $1 were `]').

There are workarounds you can use to avoid the problem, involving adding a
set of quotes to suppress the expansion the array subscript evaluation
performs.


--
``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/