On 12nd of February 2020, Michael Paquier committed patch:

Add %x to default PROMPT1 and PROMPT2 in psql
 
%d can be used to track if the current connection is in a transaction
block or not, and adding it by default to the prompt has the advantage
to not need a modification of .psqlrc, something not possible depending
on the environment.
 
This discussion has happened across various sources, and there was a
strong consensus in favor of this change.
 
Author: Vik Fearing
Reviewed-by: Fabien Coelho
Discussion: https://postgr.es/m/09502c40-cfe1-bb29-10f9-4b3fa7b2bbb2@2ndquadrant.com

This is very simple, but cool addition.

Previously PROMPT1 and PROMPT2 were, by default, “%/%R%# “. That is, they contained:

1. %/ – name of current database
2. %R – additional marker showing at what stage of parsing are we:
   • = – new command
   • – – continuation of multiline query
   • * – inside of /* */ comment block
   • ! – if disconnected from database
   • ‘ – inside of ‘….' string
   • $ – inside of $$…$$ string
   • “ – inside of “quoted" identifier
3. %# – # or > character depending on whether user is superuser or not

Now, with this patch, between %R and %# we also have %x which can mean:

• * – we're inside transaction
• ! – inside transaction that failed, but hasn't been rolled back yet
• ? – transaction state is unknown (no connection)
• empty string – not in transaction

This will immediately show if the transaction failed.

For example, in previous Pg:

depesz=# BEGIN;
BEGIN
 
depesz=# SELECT 1/0;
ERROR:  division BY zero
 
depesz=# SELECT 1;
ERROR:  CURRENT TRANSACTION IS aborted, commands ignored until END OF TRANSACTION block

and in new one:

depesz=# BEGIN;
BEGIN
 
depesz=*# SELECT 1/0;
ERROR:  division BY zero
 
depesz=!# SELECT 1;
ERROR:  CURRENT TRANSACTION IS aborted, commands ignored until END OF TRANSACTION block

Pretty cool.

Thanks to all involved 🙂