Re: set -e not ignored in AND-OR list

On 24/11/2024 11:58, Herbert Xu wrote:
> On Sat, Nov 23, 2024 at 04:22:52AM +0100, Christoph Anton Mitterer wrote:
>>
>> @Herbert, you've said that you believe dash's behaviour is POSIX
>> compliant.
>> But I still couldn't find anything in the text which would imply
>> this... and Harald who typically knows things quite well also seems to
>> believe that POSIX doesn't allow it.
> 
> It's simple really, POSIX says:
> 
> 	or any command of an AND-OR list other than the last.
> 
> The word "command" refers to the commands that make up the AND-OR
> list.  Command substitution is not part of that at all.

Isn't it? Taking the rest of the sentence along with it:

   The -e setting shall be ignored when executing [...] any command of an
   AND-OR list other than the last.

So, given

   set -e
   test -n "$(false; echo x)" && echo x

the -e setting shall be ignored when executing

   test -n "$(false; echo x)"

That much I think is not in doubt.

What does it mean for that command to be executed? 2.9.1.1 Order of 
Processing says:

   When a given simple command is required to be executed (that is, when
   any conditional construct such as an AND-OR list or a case statement
   has not bypassed the simple command), the following expansions,
   assignments, and redirections shall all be performed from the
   beginning of the command text to the end:

     [...]
     2. [...] For all other command names, words after the word that
        produced the command name shall be subject only to regular
        expansion.
     [...]

That is, the expansion of words in a simple command is considered part 
of the execution of that command. When the "false; echo x" is being 
executed, this is part of the execution of test -n "$(false; echo x)". 
Because that test -n "$(false; echo x)" command is being executed, and 
it is a command of an AND-OR list other than the last, by what POSIX 
says, the set -e setting shall be ignored.

Cheers,
Harald van Dijk