Form login requiresAuthenticationMatcher is not used in WebFlux

[eleftherias]

Summary

When specifying a custom requiresAuthenticationMatcher in formLogin for WebFlux security, it is not used unless a custom authenticationEntryPoint is used.

Example configuration:

SecurityWebFilterChain securityWebFilter = this.http
	.authorizeExchange()
		.pathMatchers("/login", "/sign-in").permitAll()
		.anyExchange().authenticated()
		.and()
	.formLogin()
		.requiresAuthenticationMatcher(new PathPatternParserServerWebExchangeMatcher("/sign-in"))
		.and()
	.build();

Actual Behavior

Making a request to "/sign-in" does not perform authentication.
Making a POST to "/login" does perform authentication.

Expected Behavior

Making a request to "/sign-in" should perform authentication.
Making a POST to "/login" should not perform authentication.