Don't send empty startup parameters

That's also what libpq does; from src/interfaces/libpq/fe-protocol3.c

	if (conn->pguser && conn->pguser[0])
		ADD_STARTUP_OPTION("user", conn->pguser);
	if (conn->dbName && conn->dbName[0])
		ADD_STARTUP_OPTION("database", conn->dbName);
	if (conn->replication && conn->replication[0])
		ADD_STARTUP_OPTION("replication", conn->replication);
	if (conn->pgoptions && conn->pgoptions[0])
		ADD_STARTUP_OPTION("options", conn->pgoptions);
	if (conn->send_appname) {
		/* Use appname if present, otherwise use fallback */
		val = conn->appname ? conn->appname : conn->fbappname;
		if (val && val[0])
			ADD_STARTUP_OPTION("application_name", val);
	}
	if (conn->client_encoding_initial && conn->client_encoding_initial[0])
		ADD_STARTUP_OPTION("client_encoding", conn->client_encoding_initial);

Sending an empty value works for most systems, but not in Supavisor due
to a bug there. Easy enough to fix here, so why not.

Fixes #1259

Co-authored-by: Martin Tournoij <martin@arp242.net>

Author: dossy

CHANGELOG.md

@@ -1,3 +1,17 @@
+v1.11.2 (2025-02-10)
+--------------------
+This fixes two regressions:
+
+- Don't send startup parameters if there is no value, improving compatibility
+  with Supavisor ([#1260]).
+
+- Don't send `dbname` as a startup parameter if `database=[..]` is used in the
+  connection string. It's recommended to use dbname=, as database= is not a
+  libpq option, and only worked by accident previously. ([#1261])
+
+[#1260]: https://github.com/lib/pq/pull/1260
+[#1261]: https://github.com/lib/pq/pull/1261
+
 v1.11.1 (2025-01-29)
 --------------------
 This fixes two regressions present in the v1.11.0 release:

conn.go

@@ -1188,20 +1188,27 @@ func (cn *conn) startup(cfg Config) error {
 	w := cn.writeBuf(0)
 	w.int32(proto.ProtocolVersion30)
 
-	w.string("user")
-	w.string(cfg.User)
-	w.string("database")
-	w.string(cfg.Database)
+	if cfg.User != "" {
+		w.string("user")
+		w.string(cfg.User)
+	}
+	if cfg.Database != "" {
+		w.string("database")
+		w.string(cfg.Database)
+	}
 	// w.string("replication") // Sent by libpq, but we don't support that.
-	w.string("options")
-	w.string(cfg.Options)
+	if cfg.Options != "" {
+		w.string("options")
+		w.string(cfg.Options)
+	}
 	if cfg.ApplicationName != "" {
 		w.string("application_name")
 		w.string(cfg.ApplicationName)
 	}
-	w.string("client_encoding")
-	w.string(cfg.ClientEncoding)
-
+	if cfg.ClientEncoding != "" {
+		w.string("client_encoding")
+		w.string(cfg.ClientEncoding)
+	}
 	for k, v := range cfg.Runtime {
 		w.string(k)
 		w.string(v)