On 5th of September 2017, Tom Lane committed patch:
Add \gdesc psql command. This command acts somewhat like \g, but instead of executing the query buffer, it merely prints a description of the columns that the query result would have. (Of course, this still requires parsing the query; if parse analysis fails, you get an error anyway.) We accomplish this using an unnamed prepared statement, which should be invisible to psql users. Pavel Stehule, reviewed by Fabien Coelho Discussion: https://postgr.es/m/CAFj8pRBhYVvO34FU=EKb=nAF5t3b++krKt1FneCmR0kuF5m-QA@mail.gmail.com
Continue reading Waiting for PostgreSQL 11 – Add \gdesc psql command.