Optimization works only on specific syntax? (was [ANNOUNCE] nftables 1.0.5 release)

[Amish <anon.amish@gmail.com>]

On 10/08/22 01:24, Pablo Neira Ayuso wrote:
> - Fixes for the -o/--optimize, run this --optimize option to automagically
>    compact your ruleset using sets, maps and concatenations, eg.
>
>       # cat ruleset.nft
>       table ip x {
>              chain y {
>                      type nat hook postrouting priority srcnat; policy drop;
>                      ip saddr 1.1.1.1 tcp dport 8000 snat to 4.4.4.4:80
>                      ip saddr 2.2.2.2 tcp dport 8001 snat to 5.5.5.5:90
>              }
>       }
>
>       # nft -o -c -f ruleset.nft
>       Merging:
>       ruleset.nft:4:3-52:                ip saddr 1.1.1.1 tcp dport 8000 snat to 4.4.4.4:80
>       ruleset.nft:5:3-52:                ip saddr 2.2.2.2 tcp dport 8001 snat to 5.5.5.5:90
>       into:
>              snat to ip saddr . tcp dport map { 1.1.1.1 . 8000 : 4.4.4.4 . 80, 2.2.2.2 . 8001 : 5.5.5.5 . 90 }

This optimization seems to be working only on specific syntax.

If I mention same thing with alternative syntax, there is no suggestion 
to optimize.

# cat ruleset.nft
add table ip x
add chain ip x y { type nat hook postrouting priority srcnat; policy drop; }
add rule ip x y ip saddr 1.1.1.1 tcp dport 8000 snat to 4.4.4.4:80
add rule ip x y ip saddr 2.2.2.2 tcp dport 8001 snat to 5.5.5.5:90

# nft -o -c -f ruleset.nft
<no output with exit code 0>

Which means that no optimization is suggested but check passed successfully.

I was expecting that it will reply with:

Merging:
  ...
into:
     add rule ip x y snat to ip saddr . tcp dport map { 1.1.1.1 . 8000 : 
4.4.4.4 . 80, 2.2.2.2 . 8001 : 5.5.5.5 . 90 }

OR if it can not translate to exact syntax then atleast it should 
mention that there is possibility to optimize the rules.

Is there any reason? Am I doing something wrong?

Please suggest.

Thank you and best regards,

Amish