namref dicussion continued: [PATCH] export -r reference

[Piotr Grzybowski]

Hey,

 after another discussion with Grisha, and following one of his remarks, I 
kindly request your opinion on the attached patch (like: bad, not needed, 
already done, weak as it stands, harmful, etc.). It addresses the exporting of 
identifiers with have nameref attribute set.
 at the moment we have:

#a=10; declare -nx ra=a; bash -c 'echo "a:$a, ra:$ra, ra_excl:${!ra}."' 
a:, ra:a, ra_excl:.
#a=10; declare -n ra=a; export ra; bash -c 'echo "a:$a, ra:$ra, 
ra_excl:${!ra}."'
a:10, ra:a, ra_excl:10

so either you get reference value exported (not very useful, and probably not 
the intent when typing declare -nx reference=variable;), or you get the 
referenced variable exported, which is not necessarily expected, together with 
the variable with the reference value.

The patch makes both of them work the same, and resolving the reference at 
export:

bash-4.4$ a=10; declare -nx ra=a; bash -c 'echo "a:$a, ra:$ra, 
ra_excl:${!ra}."' 
a:, ra:10, ra_excl:.
bash-4.4$ a=10; declare -n ra=a; export ra; bash -c 'echo "a:$a, ra:$ra, 
ra_excl:${!ra}."'
a:, ra:10, ra_excl:.

and also introduces a way to recover the current behaviour with the exporting 
of the target variable:

bash-4.4$ a=10; declare -n ra=a; export -r ra; bash -c 'echo "a:$a, ra:$ra, 
ra_excl:${!ra}."'
a:10, ra:10, ra_excl:.

there are of course other possibilities to consider, but I agree with Grisha, 
that it is worthy of at least taking a look.

cheers,
pg

follow_references_on_export.patch
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