pgsql: psql: Set variables from query result on failure when printing t

psql: Set variables from query result on failure when printing tuples

SetResultVariables() was not getting called when "printing" a result
that failed (see around PrintQueryResult), which would cause some
variables to not be set, like ROW_COUNT, SQLSTATE or ERROR. This can be
confusing as a previous result would be retained.

This state could be reached when failing to process tuples in a few
commands, like \gset when it returns no tuples, or \crosstabview. A
test is added, based on \gset.

This is arguably a bug fix, but no backpatch is done as there is a risk
of breaking scripts that rely on the previous behavior, even if they do
so accidentally.

Reported-by: amutu
Author: Japin Li
Reviewed-by: Tom Lane, Michael Paquier
Discussion: https://postgr.es/m/18134-87126d90cb4dd049@postgresql.org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/2940f1c8373cb3b43b3b42d40786b05d6e901de1

Modified Files
--------------
src/bin/psql/common.c | 6 +++---
src/test/regress/expected/psql.out | 5 +++++
src/test/regress/sql/psql.sql | 4 ++++
3 files changed, 12 insertions(+), 3 deletions(-)