Add WebFlux oauth2Login with formLogin test

Closes gh-9326

Author: Ihor Ilkevych

config/src/test/java/org/springframework/security/config/web/server/FormLoginTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -434,6 +434,11 @@ public DefaultLoginPage assertLoginFormNotPresent() {
 			return this;
 		}
 
+		public DefaultLoginPage assertLoginFormPresent() {
+			loginForm().username("");
+			return this;
+		}
+
 		public LoginForm loginForm() {
 			if (this.loginForm == null) {
 				this.loginForm = PageFactory.initElements(this.driver, LoginForm.class);

config/src/test/java/org/springframework/security/config/web/server/OAuth2LoginTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2020 the original author or authors.
+ * Copyright 2002-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,14 +33,17 @@
 import org.springframework.http.HttpHeaders;
 import org.springframework.security.authentication.ReactiveAuthenticationManager;
 import org.springframework.security.authentication.TestingAuthenticationToken;
+import org.springframework.security.authentication.UserDetailsRepositoryReactiveAuthenticationManager;
 import org.springframework.security.config.annotation.web.reactive.EnableWebFluxSecurity;
 import org.springframework.security.config.oauth2.client.CommonOAuth2Provider;
 import org.springframework.security.config.test.SpringTestRule;
+import org.springframework.security.config.users.ReactiveAuthenticationTestConfiguration;
 import org.springframework.security.core.Authentication;
 import org.springframework.security.core.AuthenticationException;
 import org.springframework.security.core.authority.AuthorityUtils;
 import org.springframework.security.core.context.SecurityContext;
 import org.springframework.security.core.context.SecurityContextImpl;
+import org.springframework.security.core.userdetails.ReactiveUserDetailsService;
 import org.springframework.security.htmlunit.server.WebTestClientHtmlUnitDriverBuilder;
 import org.springframework.security.oauth2.client.OAuth2AuthorizedClient;
 import org.springframework.security.oauth2.client.annotation.RegisteredOAuth2AuthorizedClient;
@@ -176,6 +179,24 @@ public void defaultLoginPageWithSingleClientRegistrationThenRedirect() {
 		assertThat(driver.getCurrentUrl()).startsWith("https://github.com/login/oauth/authorize");
 	}
 
+	@Test
+	public void defaultLoginPageWithSingleClientRegistrationAndFormLoginThenLinks() {
+		this.spring.register(OAuth2LoginWithSingleClientRegistrations.class, OAuth2LoginWithFormLogin.class).autowire();
+		// @formatter:off
+		WebTestClient webTestClient = WebTestClientBuilder
+				.bindToWebFilters(new GitHubWebFilter(), this.springSecurity)
+				.build();
+		WebDriver driver = WebTestClientHtmlUnitDriverBuilder
+				.webTestClientSetup(webTestClient)
+				.build();
+		FormLoginTests.HomePage.to(driver, FormLoginTests.DefaultLoginPage.class)
+				.assertAt()
+				.assertLoginFormPresent()
+				.oauth2Login()
+					.assertClientRegistrationByName(OAuth2LoginTests.github.getClientName());
+		// @formatter:on
+	}
+
 	// gh-8118
 	@Test
 	public void defaultLoginPageWithSingleClientRegistrationAndXhrRequestThenDoesNotRedirectForAuthorization() {
@@ -584,6 +605,30 @@ String home(@RegisteredOAuth2AuthorizedClient("github") OAuth2AuthorizedClient a
 
 	}
 
+	@Configuration
+	static class OAuth2LoginWithFormLogin {
+
+		@Bean
+		SecurityWebFilterChain springSecurityFilter(ServerHttpSecurity http) {
+			ReactiveUserDetailsService reactiveUserDetailsService = ReactiveAuthenticationTestConfiguration
+					.userDetailsService();
+			ReactiveAuthenticationManager authenticationManager = new UserDetailsRepositoryReactiveAuthenticationManager(
+					reactiveUserDetailsService);
+			http.authenticationManager(authenticationManager);
+			// @formatter:off
+			http
+				.authorizeExchange()
+					.anyExchange().authenticated()
+					.and()
+				.oauth2Login()
+					.and()
+				.formLogin();
+			// @formatter:on
+			return http.build();
+		}
+
+	}
+
 	@Configuration
 	static class OAuth2LoginMockAuthenticationManagerConfig {