BUG #14457: Using hyphens/dashes in synchronous_standby_names fails with "invalid value"

The following bug has been logged on the website:

Bug reference: 14457
Logged by: Andreas Ntaflos
Email address: daff(at)ptmx(dot)at
PostgreSQL version: 9.6.1
Operating system: Ubuntu 14.04
Description:

Hi all,

It seems that hyphens or dashes in the value of synchronous_standby_names
are not accepted.

When setting

synchronous_standby_names = 'db02-prod'

and reloading PostgreSQL the following message appears in the logs:

LOG: invalid value for parameter "synchronous_standby_names": "db02-prod"

Changing the value to "db02prod" or "*" seems to satisfy PostgreSQL.

The application_name setting in a standby's primary_conninfo accepts
printable ASCII characters such as hyphens, therefore
synchronous_standby_names should as well, no? PostgreSQL 9.5 is fine with
such values, PostgreSQL 9.6 is not. This is probably an unintended side
effect of the new supported syntax for specifying synchronous standbys.