Make psql reject attempts to set special variables to invalid values.

Previously, if the user set a special variable such as ECHO to an
unrecognized value, psql would bleat but store the new value anyway, and
then fall back to a default setting for the behavior controlled by the
variable.  This was agreed to be a not particularly good idea.  With
this patch, invalid values result in an error message and no change in
state.

(But this applies only to variables that affect psql's behavior; purely
informational variables such as ENCODING can still be set to random
values.)

To do this, modify the API for psql's assign-hook functions so that they
can return an OK/not OK result, and give them the responsibility for
printing error messages when they reject a value.  Adjust the APIs for
ParseVariableBool and ParseVariableNum to support the new behavior
conveniently.

In passing, document the variable VERSION, which had somehow escaped that.
And improve the quite-inadequate commenting in psql/variables.c.

Daniel Vérité, reviewed by Rahila Syed, some further tweaking by me

Discussion: https://postgr.es/m/7356e741-fa59-4146-a8eb-cf95fd6b21fb@mm

1 files changed, 1 insertions, 1 deletions

diff --git a/src/bin/psql/input.c b/src/bin/psql/input.c
index 972bea4cbf8..3e3e97ad0d2 100644
--- a/src/bin/psql/input.c
+++ b/src/bin/psql/input.c
@@ -541,7 +541,7 @@ finishInput(void)
 	{
 		int			hist_size;
 
-		hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1, true);
+		hist_size = GetVariableNum(pset.vars, "HISTSIZE", 500, -1);
 		(void) saveHistory(psql_history, hist_size);
 		free(psql_history);
 		psql_history = NULL;