Aborted pg_dump run empties existing archive file

[Ken Winter <ken@xxxxxxxxxxx>]

I just discovered that a run of pg_dump that gets aborted empties any pre-existing backup file of the same name.  It happens whether the run was deliberately canceled by the user or just failed because of a bad password (as in the example below). 

~/dba$ pg_dump --host=localhost -U ken  --format=c --file=mess_development.bak --no-owner --no-privileges mess_development
Password: <CORRECT PASSWORD ENTERED>

~/dba$ ls -l mess_development.bak
-rw-rw-r-- 1 ken ken 87070 May 26 14:20 mess_development.bak

~/dba$ pg_dump --host=localhost -U ken  --format=c --file=mess_development.bak --no-owner --no-privileges mess_development
Password: <BAD PASSWORD ENTERED>
pg_dump: [archiver (db)] connection to database "mess_development" failed: FATAL:  password authentication failed for user "ken"
FATAL:  password authentication failed for user "ken"
 
~/dba$ ls -l mess_development.bak
-rw-rw-r-- 1 ken ken 0 May 26 14:21 mess_development.bak

~/dba$

This is troubling because I can imagine a disaster scenario where one loses one's previous backup and, perhaps because of a forgotten password, can't generate a new one.  (This scenario hasn't happened to me yet, but seems like it could.)  In general, a failed run of a piece of software should leave everything unchanged.  So maybe this is a bug that needs to be fixed?

~ Ken