Merge branch '2.3.x' into 2.4.x

Closes gh-26124

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/cloud/CloudPlatform.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -29,6 +29,7 @@ import org.springframework.core.env.StandardEnvironment;
  *
  * @author Phillip Webb
  * @author Brian Clozel
+ * @author Nguyen Sach
  * @since 1.3.0
  */
 public enum CloudPlatform {
@@ -140,7 +141,8 @@ public enum CloudPlatform {
 	 * @return if the platform is active.
 	 */
 	public boolean isActive(Environment environment) {
-		return isEnforced(environment) || isDetected(environment);
+		String platformProperty = environment.getProperty(PROPERTY_NAME);
+		return isEnforced(platformProperty) || (platformProperty == null && isDetected(environment));
 	}
 
 	/**

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/cloud/CloudPlatformTests.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 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.
@@ -19,6 +19,7 @@ package org.springframework.boot.cloud;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Test;
 
@@ -36,6 +37,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * Tests for {@link CloudPlatform}.
  *
  * @author Phillip Webb
+ * @author Nguyen Sach
  */
 class CloudPlatformTests {
 
@@ -177,6 +179,16 @@ class CloudPlatformTests {
 		assertThat(CloudPlatform.KUBERNETES.isEnforced(binder)).isFalse();
 	}
 
+	void isActiveWhenNoCloudPlatformIsEnforcedAndHasKubernetesServiceHostAndKubernetesServicePort() {
+		Map<String, Object> envVars = new HashMap<>();
+		envVars.put("EXAMPLE_SERVICE_HOST", "---");
+		envVars.put("EXAMPLE_SERVICE_PORT", "8080");
+		Environment environment = getEnvironmentWithEnvVariables(envVars);
+		((MockEnvironment) environment).setProperty("spring.main.cloud-platform", "none");
+		assertThat(Stream.of(CloudPlatform.values()).filter((platform) -> platform.isActive(environment)))
+				.containsExactly(CloudPlatform.NONE);
+	}
+
 	private Environment getEnvironmentWithEnvVariables(Map<String, Object> environmentVariables) {
 		MockEnvironment environment = new MockEnvironment();
 		PropertySource<?> propertySource = new SystemEnvironmentPropertySource(