NullPointerException at SingleHostConnectionFunction#getCredentials when configuration password is null

[janainamendonca]

Bug Report

This is a regression from #613

Versions

• Driver: 1.0.3.RELEASE
• Database: CockroachDB
• Java: 21
• OS: macOS 14.1.2

Current Behavior

The PostgresqlConnectionConfiguration.Builder allows to build a configuration where the password field is null (instead of an empty publisher), it blows up when SingleHostConnectionFunction#getCredentials is called as it tries to create a Mono with null value.

Stack trace

Caused by: java.lang.NullPointerException: publisher
	at java.base/java.util.Objects.requireNonNull(Objects.java:259)
	at reactor.core.publisher.MonoFromPublisher.<init>(MonoFromPublisher.java:44)
	at reactor.core.publisher.Mono.wrap(Mono.java:5383)
	at reactor.core.publisher.Mono.from(Mono.java:507)
	at io.r2dbc.postgresql.SingleHostConnectionFunction.getCredentials(SingleHostConnectionFunction.java:72)
	at io.r2dbc.postgresql.SingleHostConnectionFunction.lambda$connect$2(SingleHostConnectionFunction.java:48)
	at reactor.core.publisher.MonoDelayUntil$DelayUntilCoordinator.subscribeNextTrigger(MonoDelayUntil.java:293)
	... 29 common frames omitted

Expected behavior/code

To not fail if a password is not set to the builder given that the field used to be nullable and the change from #613 changed the behaviour making it not compatible with existing code from SpringBoot.

Possible Solution

The builder could assign a default value (Mono.empty()) to the password field