Swagger UI shows petstore swagger by default in webflux

[lagoshny]

Describe the bug
After update to Spring Boot to 3.4.4 version and springdoc webflux ui starter to 2.8.6 the main page Swagger UI
shows by default petstore swagger Open API.
I know that we can use to disable this behavior additional configuration:

springdoc:
  swagger-ui:
    disable-swagger-default-url: true

But it doesn't work because SwaggerIndexPageTransformer ignored when I open default swagger path for webflux /webjars/swagger-ui/index.html

After some research, I found that Spring added resource handler with org.springframework.web.reactive.resource.CachingResourceTransformer for path /webjars/** in org.springframework.boot.autoconfigure.web.reactive.WebFluxAutoConfiguration.WebFluxConfig#addResourceHandlers and this is used to process when I open /webjars/swagger-ui/index.html instead SwaggerIndexPageTransformer.

The problem in org.springdoc.webflux.ui.SwaggerWebFluxConfigurer#addResourceHandlers it adds SwaggerIndexPageTransformer for path /swagger-ui and it is not used when we open /webjars/swagger-ui/index.html URL.

if (DEFAULT_WEB_JARS_PREFIX_URL.equals(webjarsPrefix)) {
      swaggerUiPrefix = SWAGGER_UI_PREFIX;
      resourcePath = webjarsPrefix + SWAGGER_UI_PREFIX + DEFAULT_PATH_SEPARATOR + swaggerUiConfigProperties.getVersion();
    } else {
      swaggerUiPrefix = webjarsPrefix;
      resourcePath = DEFAULT_WEB_JARS_PREFIX_URL + DEFAULT_PATH_SEPARATOR;
    }

    registry.addResourceHandler(uiRootPath + swaggerUiPrefix + ALL_PATTERN)
        .addResourceLocations(CLASSPATH_RESOURCE_LOCATION + resourcePath)
        .resourceChain(false)
        .addResolver(swaggerResourceResolver)
        .addTransformer(swaggerIndexTransformer);

We need to add webjarsPrefix to swaggerUiPrefix and then SwaggerIndexPageTransformer will be used for path /webjars/swagger-ui that overrides default Spring CachingResourceTransformer.

To Reproduce
Steps to reproduce the behavior:

• Create Spring boot 3.4.4 project and add org.springdoc:springdoc-openapi-starter-webflux-ui:2.8.6 deps.
• Create some RestController with Dto's that used OpenAPI.
• Open swagger UI for your service, and you will see default petstroe swagger instead of your project /v3/api-docs

Expected behavior

I expected that when I set up

springdoc:
  swagger-ui:
    disable-swagger-default-url: true

then springdoc will be transforming the index page and use /v3/api-docs by default instead petstore swagger

[lagoshny]

I have opened the PR how to fix it #2970

[lagoshny]

This is a simple project how to reproduce this bug

[bnasslahsen]

@lagoshny PR merged