Adjust assorted hint messages that list all valid options.

Instead of listing all valid options, we now try to provide one
that looks similar.  Since this may be useful elsewhere, this
change introduces a new set of functions that can be reused for
similar purposes.

Author: Nathan Bossart <nathandbossart@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/b1f9f399-3a1a-b554-283f-4ae7f34608e2@enterprisedb.com

2 files changed, 15 insertions, 11 deletions

diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out
index 1cf54456e5e..ad0910e8672 100644
--- a/contrib/postgres_fdw/expected/postgres_fdw.out
+++ b/contrib/postgres_fdw/expected/postgres_fdw.out
@@ -188,7 +188,6 @@ ALTER USER MAPPING FOR public SERVER testserver1
 ALTER USER MAPPING FOR public SERVER testserver1
 	OPTIONS (ADD sslmode 'require');
 ERROR:  invalid option "sslmode"
-HINT:  Valid options in this context are: user, password, sslpassword, password_required, sslcert, sslkey
 -- But we can add valid ones fine
 ALTER USER MAPPING FOR public SERVER testserver1
 	OPTIONS (ADD sslpassword 'dummy');
@@ -9706,7 +9705,7 @@ DO $d$
     END;
 $d$;
 ERROR:  invalid option "password"
-HINT:  Valid options in this context are: service, passfile, channel_binding, connect_timeout, dbname, host, hostaddr, port, options, application_name, keepalives, keepalives_idle, keepalives_interval, keepalives_count, tcp_user_timeout, sslmode, sslcompression, sslcert, sslkey, sslrootcert, sslcrl, sslcrldir, sslsni, requirepeer, ssl_min_protocol_version, ssl_max_protocol_version, gssencmode, krbsrvname, gsslib, target_session_attrs, use_remote_estimate, fdw_startup_cost, fdw_tuple_cost, extensions, updatable, truncatable, fetch_size, batch_size, async_capable, parallel_commit, keep_connections
+HINT:  Perhaps you meant the option "passfile".
 CONTEXT:  SQL statement "ALTER SERVER loopback_nopw OPTIONS (ADD password 'dummypw')"
 PL/pgSQL function inline_code_block line 3 at EXECUTE
 -- If we add a password for our user mapping instead, we should get a different
diff --git a/contrib/postgres_fdw/option.c b/contrib/postgres_fdw/option.c
index 95dde056eba..fa80ee2a55e 100644
--- a/contrib/postgres_fdw/option.c
+++ b/contrib/postgres_fdw/option.c
@@ -90,26 +90,31 @@ postgres_fdw_validator(PG_FUNCTION_ARGS)
 		{
 			/*
 			 * Unknown option specified, complain about it. Provide a hint
-			 * with list of valid options for the object.
+			 * with a valid option that looks similar, if there is one.
 			 */
 			PgFdwOption *opt;
-			StringInfoData buf;
+			const char *closest_match;
+			ClosestMatchState match_state;
+			bool		has_valid_options = false;
 
-			initStringInfo(&buf);
+			initClosestMatch(&match_state, def->defname, 4);
 			for (opt = postgres_fdw_options; opt->keyword; opt++)
 			{
 				if (catalog == opt->optcontext)
-					appendStringInfo(&buf, "%s%s", (buf.len > 0) ? ", " : "",
-									 opt->keyword);
+				{
+					has_valid_options = true;
+					updateClosestMatch(&match_state, opt->keyword);
+				}
 			}
 
+			closest_match = getClosestMatch(&match_state);
 			ereport(ERROR,
 					(errcode(ERRCODE_FDW_INVALID_OPTION_NAME),
 					 errmsg("invalid option \"%s\"", def->defname),
-					 buf.len > 0
-					 ? errhint("Valid options in this context are: %s",
-							   buf.data)
-					 : errhint("There are no valid options in this context.")));
+					 has_valid_options ? closest_match ?
+					 errhint("Perhaps you meant the option \"%s\".",
+							 closest_match) : 0 :
+					 errhint("There are no valid options in this context.")));
 		}
 
 		/*