Re: Incorrect alias expansion within command substitution

[L A Walsh]

On 2022/01/31 20:40, Martijn Dekker wrote:
> On the latest code from the devel branch:
> GNU bash, versie 5.2.0(35)-alpha (x86_64-apple-darwin18.7.0)
>
> Reproducer script:
>
> shopt -s expand_aliases
> alias let='let --'
> set -x
> let '1 == 1'
> : $(let '1 == 1')
>
> Output:
>
> + let -- '1 == 1'
> ++ let -- -- '1 == 1'
> foo: line 5: let: --: syntax error: operand expected (error token is "-")
> + :
>
> The alias is incorrectly expanded in the command substitution, 
> duplicating the '--' argument and causing a syntax error.
>   
----
I can't say for sure, but it would be interesting if anyone else
has this result in a bash with aliases on by default:

I.e. My bash is posix compliant by default w/r/t aliases:
>  env -i /bin/bash --noprofile --norc
bash-4.4$ shopt -p expand_aliases
shopt -s expand_aliases

and it doesn't show the above error:

bash-4.4$ alias let='let --'
bash-4.4$ set -x
bash-4.4$ let '1 == 1'
+ let -- '1 == 1'
bash-4.4$ : $(let '1 == 1')
++ let -- '1 == 1'
+ :

It may not be the case, but to me, looked like the alias for 'let' had 
been disabled
in the $() subshell as per standard bash behavior of disabling aliases
on startup.

I.e. if you configure bash to be posix compliant w/r/t aliases on
shell startup, this seems to fix the above problem.