Re: declare XXX=$(false);echo $?

[Dale R. Worley]

Chet Ramey <chet.ramey@case.edu> writes:
> On 12/2/22 5:28 AM, Ulrich Windl wrote:
>> Surprisingly "declare XXX=$(false);echo $?" outputs "0" (not "1")
>> There is no indication in the manual page that "declare" ignores the
>exit code of commands being executed to set values.
>
> Why do you think it should? `declare' has a well-defined return status.

There it is, end of "SIMPLE COMMAND EXPANSION":

       If  there is a command name left after expansion, execution proceeds as
       described below.  Otherwise, the command exits.  If one of  the  expan‐
       sions  contained a command substitution, the exit status of the command
       is the exit status of the  last  command  substitution  performed.   If
       there were no command substitutions, the command exits with a status of
       zero.

and:

       declare [-aAfFgiIlnrtux] [-p] [name[=value] ...]
       typeset [-aAfFgiIlnrtux] [-p] [name[=value] ...]
              [...]
              The return value
              is 0 unless an invalid option is encountered, an attempt is made
              to define a function using ``-f foo=bar'', an attempt is made to
              assign a value to a readonly variable, an attempt is made to as‐
              sign a value to an array variable without using the compound as‐
              signment  syntax  (see  Arrays above), one of the names is not a
              valid shell variable name, an attempt is made to turn off  read‐
              only  status for a readonly variable, an attempt is made to turn
              off array status for an array variable, or an attempt is made to
              display a non-existent function with -f.

If you input "XXX=$(false)", there isn't a command name, it's a sequence
of assignments, and "the exit status of the command is the exit status
of the last command substitution performed".  But if you input "declare
XXX=$(false)", you're executing the "declare" command, and the exit
status doesn't depend on the command substitution.

Dale