Clarify that MVC components provided through WebMvcRegistrations are subject to subsequent processing and configuration by MVC #31232

Previously, I was able to disable Spring MVC's trailing slash matching using something like this:

@Configuration(proxyBeanMethods = false)
class WebMvcConfiguration {

    @Bean
    WebMvcRegistrations webMvcRegistrations() {
        return new WebMvcRegistrations() {

            @Override
            public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
                RequestMappingHandlerMapping handlerMapping = new RequestMappingHandlerMapping();
                handlerMapping.setUseTrailingSlashMatch(false);
                return handlerMapping;
            }

         };
    }

}

This doesn't work any more since 2.6.0 and the change of behavior appears to be related to introduction of PathPatternParser as the default path matching strategy.

I've put together a reproduced in https://github.com/vpavic/mcve-spring-mvc-trailing-slash.

By default, trailing slash matching is enabled and curl -sv -u user:password http://localhost:8080/resources/ (note the trailing slash) returns 200 response. There are two profiles that disable trailing slash matching - configurer and registrations. The former uses WebMvcConfigurer based approach and this works (meaning, cURL request returns 404), while the latter uses WebMvcRegistrations based approach (as in the snippet above) and this doesn't work (returns 200).

Downgrading Spring Boot to 2.5.x makes the registrations profile work as expected.

I'm reporting this here for starters because what's failing is a Spring Boot specific configuration mechanism (WebMvcRegistrations) even though it seems to me that the fix might very well be needed in the Framework.