Refactor PropertySourcesDeducer

Prior to the changes that fixed #12451,
`FilteredPropertySources` and `CompositePropertySources` were required
by the `PropertySourcesDeducer` to ensure that configuration properties binding
could see changes to the environment even when there was a
PropertySourcesPlaceholderConfigurer in the context. #12451 changed the way
property sources are adapted by `SpringConfigurationPropertySources`, removing the
need for `FilteredPropertySources` and `CompositePropertySources`.

Fixes gh-13738

Author: mbhave

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

@@ -27,7 +27,6 @@
 import org.springframework.core.env.Environment;
 import org.springframework.core.env.MutablePropertySources;
 import org.springframework.core.env.PropertySources;
-import org.springframework.util.Assert;
 
 /**
  * Utility to deduce the {@link PropertySources} to use for configuration binding.
@@ -45,20 +44,16 @@ class PropertySourcesDeducer {
 	}
 
 	public PropertySources getPropertySources() {
-		MutablePropertySources environmentPropertySources = extractEnvironmentPropertySources();
-		PropertySourcesPlaceholderConfigurer placeholderConfigurer = getSinglePropertySourcesPlaceholderConfigurer();
-		if (placeholderConfigurer == null) {
-			Assert.state(environmentPropertySources != null,
-					"Unable to obtain PropertySources from "
-							+ "PropertySourcesPlaceholderConfigurer or Environment");
-			return environmentPropertySources;
+		PropertySourcesPlaceholderConfigurer configurer = getSinglePropertySourcesPlaceholderConfigurer();
+		if (configurer != null) {
+			return configurer.getAppliedPropertySources();
 		}
-		PropertySources appliedPropertySources = placeholderConfigurer
-				.getAppliedPropertySources();
-		if (environmentPropertySources == null) {
-			return appliedPropertySources;
+		MutablePropertySources sources = extractEnvironmentPropertySources();
+		if (sources != null) {
+			return sources;
 		}
-		return merge(environmentPropertySources, appliedPropertySources);
+		throw new IllegalStateException("Unable to obtain PropertySources from "
+				+ "PropertySourcesPlaceholderConfigurer or Environment");
 	}
 
 	private MutablePropertySources extractEnvironmentPropertySources() {
@@ -84,12 +79,4 @@ private PropertySourcesPlaceholderConfigurer getSinglePropertySourcesPlaceholder
 		return null;
 	}
 
-	private PropertySources merge(PropertySources environmentPropertySources,
-			PropertySources appliedPropertySources) {
-		FilteredPropertySources filtered = new FilteredPropertySources(
-				appliedPropertySources,
-				PropertySourcesPlaceholderConfigurer.ENVIRONMENT_PROPERTIES_PROPERTY_SOURCE_NAME);
-		return new CompositePropertySources(filtered, environmentPropertySources);
-	}
-
 }

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

@@ -25,6 +25,7 @@
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Properties;
 import java.util.Set;
 
 import javax.annotation.PostConstruct;
@@ -352,6 +353,15 @@ public void loadWithPropertyPlaceholderValueShouldBind() {
 		assertThat(bean.getValue()).isEqualTo("foo");
 	}
 
+	@Test
+	public void loadWithPropertyPlaceholderShouldNotAlterPropertySourceOrder() {
+		load(WithPropertyPlaceholderWithLocalPropertiesValueConfiguration.class,
+				"com.example.bar=a");
+		SimplePrefixedProperties bean = this.context
+				.getBean(SimplePrefixedProperties.class);
+		assertThat(bean.getBar()).isEqualTo("a");
+	}
+
 	@Test
 	public void loadWhenHasPostConstructShouldTriggerPostConstructWithBoundBean() {
 		MockEnvironment environment = new MockEnvironment();
@@ -959,6 +969,21 @@ public static PropertySourcesPlaceholderConfigurer configurer() {
 
 	}
 
+	@Configuration
+	@EnableConfigurationProperties(SimplePrefixedProperties.class)
+	static class WithPropertyPlaceholderWithLocalPropertiesValueConfiguration {
+
+		@Bean
+		public static PropertySourcesPlaceholderConfigurer configurer() {
+			PropertySourcesPlaceholderConfigurer placeholderConfigurer = new PropertySourcesPlaceholderConfigurer();
+			Properties properties = new Properties();
+			properties.put("com.example.bar", "b");
+			placeholderConfigurer.setProperties(properties);
+			return placeholderConfigurer;
+		}
+
+	}
+
 	@Configuration
 	@EnableConfigurationProperties
 	static class WithFactoryBeanConfiguration {