In successful pg_recvlogical, end PGRES_COPY_OUT cleanly.
pg_recvlogical merely called PQfinish(), so the backend sent messages
after the disconnect. When that caused EPIPE in internal_flush(),
before a LogicalConfirmReceivedLocation(), the next pg_recvlogical would
repeat already-acknowledged records. Whether or not the defect causes
EPIPE, post-disconnect messages could contain an ErrorResponse that the
user should see. One properly ends PGRES_COPY_OUT by repeating
PQgetCopyData() until it returns a negative value. Augment one of the
tests to cover the case of WAL past --endpos. Back-patch to v10, where
commit
7c030783a5bd07cadffc2a1018bc33119a4c7505 first appeared. Before
that commit, pg_recvlogical never reached PGRES_COPY_OUT.
Reported by Thomas Munro.
Discussion: https://postgr.es/m/CAEepm=1MzM2Z_xNe4foGwZ1a+MO_2S9oYDq3M5D11=JDU_+0Nw@mail.gmail.com