Merge branch 'main' into 4.0.x

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/ConfigurationPropertyName.java

@@ -543,25 +543,24 @@ public final class ConfigurationPropertyName implements Comparable<Configuration
 
 	@Override
 	public String toString() {
-		return toString(ToStringFormat.DEFAULT);
+		return toString(ToStringFormat.DEFAULT, false);
 	}
 
-	String toString(ToStringFormat format) {
+	String toString(ToStringFormat format, boolean upperCase) {
 		String string = this.string[format.ordinal()];
 		if (string == null) {
 			string = buildToString(format);
 			this.string[format.ordinal()] = string;
 		}
-		return string;
+		return (!upperCase) ? string : string.toUpperCase(Locale.ENGLISH);
 	}
 
 	private String buildToString(ToStringFormat format) {
 		return switch (format) {
 			case DEFAULT -> buildDefaultToString();
-			case SYSTEM_ENVIRONMENT ->
-				buildSimpleToString('_', (i) -> getElement(i, Form.UNIFORM).toUpperCase(Locale.ENGLISH));
-			case LEGACY_SYSTEM_ENVIRONMENT -> buildSimpleToString('_',
-					(i) -> getElement(i, Form.ORIGINAL).replace('-', '_').toUpperCase(Locale.ENGLISH));
+			case SYSTEM_ENVIRONMENT -> buildSimpleToString('_', (i) -> getElement(i, Form.UNIFORM));
+			case LEGACY_SYSTEM_ENVIRONMENT ->
+				buildSimpleToString('_', (i) -> getElement(i, Form.ORIGINAL).replace('-', '_'));
 		};
 	}
 

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SpringConfigurationPropertySource.java

@@ -16,6 +16,7 @@
 
 package org.springframework.boot.context.properties.source;
 
+import java.util.Locale;
 import java.util.Map;
 import java.util.Random;
 
@@ -109,7 +110,8 @@ class SpringConfigurationPropertySource implements ConfigurationPropertySource {
 	}
 
 	Object getSystemEnvironmentProperty(Map<String, Object> systemEnvironment, String name) {
-		return systemEnvironment.get(name);
+		Object value = systemEnvironment.get(name);
+		return (value != null) ? value : systemEnvironment.get(name.toLowerCase(Locale.ROOT));
 	}
 
 	@Override

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/properties/source/SystemEnvironmentPropertyMapper.java

@@ -16,8 +16,6 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.Arrays;
-import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
 import java.util.function.BiPredicate;
@@ -42,12 +40,10 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 
 	@Override
 	public List<String> map(ConfigurationPropertyName configurationPropertyName) {
-		String name = configurationPropertyName.toString(ToStringFormat.SYSTEM_ENVIRONMENT);
-		String legacyName = configurationPropertyName.toString(ToStringFormat.LEGACY_SYSTEM_ENVIRONMENT);
-		if (name.equals(legacyName)) {
-			return Collections.singletonList(name);
-		}
-		return Arrays.asList(name, legacyName);
+		return List.of(configurationPropertyName.toString(ToStringFormat.SYSTEM_ENVIRONMENT, true),
+				configurationPropertyName.toString(ToStringFormat.LEGACY_SYSTEM_ENVIRONMENT, true),
+				configurationPropertyName.toString(ToStringFormat.SYSTEM_ENVIRONMENT, false),
+				configurationPropertyName.toString(ToStringFormat.LEGACY_SYSTEM_ENVIRONMENT, false));
 	}
 
 	@Override

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/source/SpringIterableConfigurationPropertySourceTests.java

@@ -152,10 +152,12 @@ class SpringIterableConfigurationPropertySourceTests {
 	}
 
 	@Test
-	void containsDescendantOfWhenSystemEnvironmentPropertySourceShouldLegacyProperty() {
+	void containsDescendantOfWhenSystemEnvironmentPropertySourceShouldSupportLegacyProperty() {
 		Map<String, Object> source = new LinkedHashMap<>();
 		source.put("FOO_BAR_BAZ_BONG", "bing");
 		source.put("FOO_ALPHABRAVO_GAMMA", "delta");
+		source.put("loo_bar_baz_bong", "bing");
+		source.put("loo_alphabravo_gamma", "delta");
 		SystemEnvironmentPropertySource propertySource = new SystemEnvironmentPropertySource(
 				StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, source);
 		SpringIterableConfigurationPropertySource adapter = new SpringIterableConfigurationPropertySource(
@@ -166,6 +168,27 @@ class SpringIterableConfigurationPropertySourceTests {
 			.isEqualTo(ConfigurationPropertyState.PRESENT);
 		assertThat(adapter.containsDescendantOf(ConfigurationPropertyName.of("foo.blah")))
 			.isEqualTo(ConfigurationPropertyState.ABSENT);
+		assertThat(adapter.containsDescendantOf(ConfigurationPropertyName.of("loo.bar-baz")))
+			.isEqualTo(ConfigurationPropertyState.PRESENT);
+		assertThat(adapter.containsDescendantOf(ConfigurationPropertyName.of("loo.alpha-bravo")))
+			.isEqualTo(ConfigurationPropertyState.PRESENT);
+		assertThat(adapter.containsDescendantOf(ConfigurationPropertyName.of("loo.blah")))
+			.isEqualTo(ConfigurationPropertyState.ABSENT);
+	}
+
+	@Test
+	void getConfigurationPropertyWhenSystemEnvironmentPropertySourceShouldSupportLegacyProperty() {
+		Map<String, Object> source = new LinkedHashMap<>();
+		source.put("TEST_VALUE_UPPER", "upper");
+		source.put("test_value_lower", "lower");
+		SystemEnvironmentPropertySource propertySource = new SystemEnvironmentPropertySource(
+				StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME, source);
+		SpringIterableConfigurationPropertySource adapter = new SpringIterableConfigurationPropertySource(
+				propertySource, true, SystemEnvironmentPropertyMapper.INSTANCE, DefaultPropertyMapper.INSTANCE);
+		assertThat(adapter.getConfigurationProperty(ConfigurationPropertyName.of("test.value-upper")).getValue())
+			.isEqualTo("upper");
+		assertThat(adapter.getConfigurationProperty(ConfigurationPropertyName.of("test.value-lower")).getValue())
+			.isEqualTo("lower");
 	}
 
 	@Test