Fix ordering of properties and yaml files

Fixes gh-24719

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/StandardConfigDataLocationResolver.java

@@ -16,9 +16,11 @@
 
 package org.springframework.boot.context.config;
 
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
+import java.util.Deque;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
@@ -171,11 +173,22 @@ public class StandardConfigDataLocationResolver
 			String directory, String profile) {
 		Set<StandardConfigDataReference> references = new LinkedHashSet<>();
 		for (String name : this.configNames) {
-			for (PropertySourceLoader propertySourceLoader : this.propertySourceLoaders) {
-				for (String extension : propertySourceLoader.getFileExtensions()) {
-					StandardConfigDataReference reference = new StandardConfigDataReference(configDataLocation,
-							directory, directory + name, profile, extension, propertySourceLoader);
-					references.add(reference);
+			Deque<StandardConfigDataReference> referencesForName = getReferencesForConfigName(name, configDataLocation,
+					directory, profile);
+			references.addAll(referencesForName);
+		}
+		return references;
+	}
+
+	private Deque<StandardConfigDataReference> getReferencesForConfigName(String name,
+			ConfigDataLocation configDataLocation, String directory, String profile) {
+		Deque<StandardConfigDataReference> references = new ArrayDeque<>();
+		for (PropertySourceLoader propertySourceLoader : this.propertySourceLoaders) {
+			for (String extension : propertySourceLoader.getFileExtensions()) {
+				StandardConfigDataReference reference = new StandardConfigDataReference(configDataLocation, directory,
+						directory + name, profile, extension, propertySourceLoader);
+				if (!references.contains(reference)) {
+					references.addFirst(reference);
 				}
 			}
 		}

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/config/ConfigDataEnvironmentPostProcessorIntegrationTests.java

@@ -135,6 +135,13 @@ class ConfigDataEnvironmentPostProcessorIntegrationTests {
 		assertThat(property).isEqualTo("frompropertiesfile");
 	}
 
+	@Test
+	void runWhenPropertiesAndYamlShouldPreferProperties() {
+		ConfigurableApplicationContext context = this.application.run();
+		String property = context.getEnvironment().getProperty("duplicate");
+		assertThat(property).isEqualTo("properties");
+	}
+
 	@Test
 	void runWhenMultipleCustomNamesLoadsEachName() {
 		ConfigurableApplicationContext context = this.application

spring-boot-project/spring-boot/src/test/resources/application.properties

@@ -3,3 +3,4 @@ value: 1234
 my.property: fromapplicationproperties
 sample.app.test.prop: *
 my.placeholder: ${my.fallback}
+duplicate=properties

spring-boot-project/spring-boot/src/test/resources/application.yml

@@ -0,0 +1 @@
+duplicate: yaml