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, 0 insertions, 1 deletions

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index e1b04de0132..6e3acdc416e 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -841,7 +841,6 @@ StoreQueryTuple(const PGresult *result)
 
 			if (!SetVariable(pset.vars, varname, value))
 			{
-				psql_error("could not set variable \"%s\"\n", varname);
 				free(varname);
 				success = false;
 				break;