Drop environment variable "__" list support

Remove support for the `__` environment variable list shortcut in order
to reduce complexity. The shortcut was developed before the new `Binder`
code was fully formed and isn't really necessary now since comma-lists
can be converted automatically.

Fixes gh-11410

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

@@ -19,7 +19,6 @@ package org.springframework.boot.context.properties.source;
 import java.util.Collections;
 import java.util.List;
 
-import org.springframework.core.env.PropertySource;
 import org.springframework.util.ObjectUtils;
 
 /**
@@ -44,7 +43,7 @@ final class DefaultPropertyMapper implements PropertyMapper {
 	}
 
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
+	public List<PropertyMapping> map(
 			ConfigurationPropertyName configurationPropertyName) {
 		// Use a local copy in case another thread changes things
 		LastMapping<ConfigurationPropertyName> last = this.lastMappedConfigurationPropertyName;
@@ -60,8 +59,7 @@ final class DefaultPropertyMapper implements PropertyMapper {
 	}
 
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
-			String propertySourceName) {
+	public List<PropertyMapping> map(String propertySourceName) {
 		// Use a local copy in case another thread changes things
 		LastMapping<String> last = this.lastMappedPropertyName;
 		if (last != null && last.isFrom(propertySourceName)) {

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

@@ -43,20 +43,16 @@ interface PropertyMapper {
 	/**
 	 * Provide mappings from a {@link ConfigurationPropertySource}
 	 * {@link ConfigurationPropertyName}.
-	 * @param propertySource the property source
 	 * @param configurationPropertyName the name to map
 	 * @return a stream of mappings or {@code Stream#empty()}
 	 */
-	List<PropertyMapping> map(PropertySource<?> propertySource,
-			ConfigurationPropertyName configurationPropertyName);
+	List<PropertyMapping> map(ConfigurationPropertyName configurationPropertyName);
 
 	/**
 	 * Provide mappings from a {@link PropertySource} property name.
-	 * @param propertySource the property source
 	 * @param propertySourceName the name to map
 	 * @return a stream of mappings or {@code Stream#empty()}
 	 */
-	List<PropertyMapping> map(PropertySource<?> propertySource,
-			String propertySourceName);
+	List<PropertyMapping> map(String propertySourceName);
 
 }

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

@@ -16,8 +16,6 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.function.Function;
-
 import org.springframework.core.env.PropertySource;
 
 /**
@@ -34,8 +32,6 @@ class PropertyMapping {
 
 	private final ConfigurationPropertyName configurationPropertyName;
 
-	private final Function<Object, Object> valueExtractor;
-
 	/**
 	 * Create a new {@link PropertyMapper} instance.
 	 * @param propertySourceName the {@link PropertySource} name
@@ -44,22 +40,8 @@ class PropertyMapping {
 	 */
 	PropertyMapping(String propertySourceName,
 			ConfigurationPropertyName configurationPropertyName) {
-		this(propertySourceName, configurationPropertyName, Function.identity());
-	}
-
-	/**
-	 * Create a new {@link PropertyMapper} instance.
-	 * @param propertySourceName the {@link PropertySource} name
-	 * @param configurationPropertyName the {@link ConfigurationPropertySource}
-	 * {@link ConfigurationPropertyName}
-	 * @param valueExtractor the extractor used to obtain the value
-	 */
-	PropertyMapping(String propertySourceName,
-			ConfigurationPropertyName configurationPropertyName,
-			Function<Object, Object> valueExtractor) {
 		this.propertySourceName = propertySourceName;
 		this.configurationPropertyName = configurationPropertyName;
-		this.valueExtractor = valueExtractor;
 	}
 
 	/**
@@ -81,14 +63,6 @@ class PropertyMapping {
 
 	}
 
-	/**
-	 * Return a function that can be used to extract the {@link PropertySource} value.
-	 * @return the value extractor (never {@code null})
-	 */
-	public Function<Object, Object> getValueExtractor() {
-		return this.valueExtractor;
-	}
-
 	/**
 	 * Return if this mapping is applicable for the given
 	 * {@link ConfigurationPropertyName}.

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

@@ -40,7 +40,7 @@ import org.springframework.util.Assert;
  * <p>
  * Each {@link ConfigurationPropertySource#getConfigurationProperty
  * getConfigurationProperty} call attempts to
- * {@link PropertyMapper#map(PropertySource, ConfigurationPropertyName) map} the
+ * {@link PropertyMapper#map(ConfigurationPropertyName) map} the
  * {@link ConfigurationPropertyName} to one or more {@code String} based names. This
  * allows fast property resolution for well formed property sources.
  * <p>
@@ -85,7 +85,7 @@ class SpringConfigurationPropertySource implements ConfigurationPropertySource {
 	@Override
 	public ConfigurationProperty getConfigurationProperty(
 			ConfigurationPropertyName name) {
-		List<PropertyMapping> mappings = getMapper().map(getPropertySource(), name);
+		List<PropertyMapping> mappings = getMapper().map(name);
 		return find(mappings, name);
 	}
 
@@ -112,7 +112,6 @@ class SpringConfigurationPropertySource implements ConfigurationPropertySource {
 		if (value == null) {
 			return null;
 		}
-		value = mapping.getValueExtractor().apply(value);
 		ConfigurationPropertyName configurationPropertyName = mapping
 				.getConfigurationPropertyName();
 		Origin origin = PropertySourceOrigin.get(this.propertySource, propertySourceName);
@@ -215,10 +214,10 @@ class SpringConfigurationPropertySource implements ConfigurationPropertySource {
 		}
 
 		@Override
-		public List<PropertyMapping> map(PropertySource<?> propertySource,
+		public List<PropertyMapping> map(
 				ConfigurationPropertyName configurationPropertyName) {
 			try {
-				return this.mapper.map(propertySource, configurationPropertyName);
+				return this.mapper.map(configurationPropertyName);
 			}
 			catch (Exception ex) {
 				return Collections.emptyList();
@@ -226,10 +225,9 @@ class SpringConfigurationPropertySource implements ConfigurationPropertySource {
 		}
 
 		@Override
-		public List<PropertyMapping> map(PropertySource<?> propertySource,
-				String propertySourceName) {
+		public List<PropertyMapping> map(String propertySourceName) {
 			try {
-				return this.mapper.map(propertySource, propertySourceName);
+				return this.mapper.map(propertySourceName);
 			}
 			catch (Exception ex) {
 				return Collections.emptyList();

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

@@ -119,7 +119,7 @@ class SpringIterableConfigurationPropertySource extends SpringConfigurationPrope
 		String[] names = getPropertySource().getPropertyNames();
 		mappings = new ArrayList<>(names.length);
 		for (String name : names) {
-			mappings.addAll(getMapper().map(getPropertySource(), name));
+			mappings.addAll(getMapper().map(name));
 		}
 		mappings = Collections.unmodifiableList(mappings);
 		if (cache != null) {

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

@@ -21,12 +21,9 @@ import java.util.Collections;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Set;
-import java.util.function.Function;
 import java.util.stream.IntStream;
 
 import org.springframework.boot.context.properties.source.ConfigurationPropertyName.Form;
-import org.springframework.core.env.PropertySource;
-import org.springframework.util.StringUtils;
 
 /**
  * {@link PropertyMapper} for system environment variables. Names are mapped by removing
@@ -52,7 +49,7 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 	}
 
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
+	public List<PropertyMapping> map(
 			ConfigurationPropertyName configurationPropertyName) {
 		Set<String> names = new LinkedHashSet<>();
 		names.add(convertName(configurationPropertyName));
@@ -60,39 +57,15 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 		List<PropertyMapping> result = new ArrayList<>();
 		names.forEach((name) -> result
 				.add(new PropertyMapping(name, configurationPropertyName)));
-		if (isListShortcutPossible(configurationPropertyName)) {
-			result.addAll(mapListShortcut(propertySource, configurationPropertyName));
-		}
 		return result;
 	}
 
-	private boolean isListShortcutPossible(ConfigurationPropertyName name) {
-		return (name.isLastElementIndexed() && isNumber(name.getLastElement(Form.UNIFORM))
-				&& name.getNumberOfElements() >= 1);
-	}
-
-	private List<PropertyMapping> mapListShortcut(PropertySource<?> propertySource,
-			ConfigurationPropertyName name) {
-		String result = convertName(name, name.getNumberOfElements() - 1) + "__";
-		if (propertySource.containsProperty(result)) {
-			int index = Integer.parseInt(name.getLastElement(Form.UNIFORM));
-			return Collections.singletonList(
-					new PropertyMapping(result, name, new ElementExtractor(index)));
-		}
-		return Collections.emptyList();
-	}
-
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
-			String propertySourceName) {
+	public List<PropertyMapping> map(String propertySourceName) {
 		ConfigurationPropertyName name = convertName(propertySourceName);
 		if (name == null || name.isEmpty()) {
 			return Collections.emptyList();
 		}
-		if (propertySourceName.endsWith("__")) {
-			return expandListShortcut(propertySourceName, name,
-					propertySource.getProperty(propertySourceName));
-		}
 		return Collections.singletonList(new PropertyMapping(propertySourceName, name));
 	}
 
@@ -106,22 +79,6 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 		}
 	}
 
-	private List<PropertyMapping> expandListShortcut(String propertySourceName,
-			ConfigurationPropertyName rootName, Object value) {
-		if (value == null) {
-			return Collections.emptyList();
-		}
-		List<PropertyMapping> mappings = new ArrayList<>();
-		String[] elements = StringUtils
-				.commaDelimitedListToStringArray(String.valueOf(value));
-		for (int i = 0; i < elements.length; i++) {
-			ConfigurationPropertyName name = rootName.append("[" + i + "]");
-			mappings.add(new PropertyMapping(propertySourceName, name,
-					new ElementExtractor(i)));
-		}
-		return mappings;
-	}
-
 	private String convertName(ConfigurationPropertyName name) {
 		return convertName(name, name.getNumberOfElements());
 	}
@@ -159,26 +116,4 @@ final class SystemEnvironmentPropertyMapper implements PropertyMapper {
 		return !hasNonDigit;
 	}
 
-	/**
-	 * Function used to extract an element from a comma list.
-	 */
-	private static class ElementExtractor implements Function<Object, Object> {
-
-		private final int index;
-
-		ElementExtractor(int index) {
-			this.index = index;
-		}
-
-		@Override
-		public Object apply(Object value) {
-			if (value == null) {
-				return null;
-			}
-			return StringUtils
-					.commaDelimitedListToStringArray(value.toString())[this.index];
-		}
-
-	}
-
 }

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

@@ -16,12 +16,8 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.Collections;
 import java.util.Iterator;
 
-import org.springframework.core.env.MapPropertySource;
-import org.springframework.core.env.PropertySource;
-
 /**
  * Abstract base class for {@link PropertyMapper} tests.
  *
@@ -38,9 +34,7 @@ public abstract class AbstractPropertyMapperTests {
 	}
 
 	protected final Iterator<String> namesFromString(String name, Object value) {
-		PropertySource<?> propertySource = new MapPropertySource("test",
-				Collections.singletonMap(name, value));
-		return getMapper().map(propertySource, name).stream()
+		return getMapper().map(name).stream()
 				.map((mapping) -> mapping.getConfigurationPropertyName().toString())
 				.iterator();
 	}
@@ -50,10 +44,8 @@ public abstract class AbstractPropertyMapperTests {
 	}
 
 	protected final Iterator<String> namesFromConfiguration(String name, String value) {
-		PropertySource<?> propertySource = new MapPropertySource("test",
-				Collections.singletonMap(name, value));
-		return getMapper().map(propertySource, ConfigurationPropertyName.of(name))
-				.stream().map(PropertyMapping::getPropertySourceName).iterator();
+		return getMapper().map(ConfigurationPropertyName.of(name)).stream()
+				.map(PropertyMapping::getPropertySourceName).iterator();
 	}
 
 }

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

@@ -71,20 +71,6 @@ public class SpringConfigurationPropertySourceTests {
 		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
 	}
 
-	@Test
-	public void getValueShouldUseExtractor() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("key", "value");
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		TestPropertyMapper mapper = new TestPropertyMapper();
-		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
-		mapper.addFromConfigurationProperty(name, "key",
-				(value) -> value.toString().replace("ue", "let"));
-		SpringConfigurationPropertySource adapter = new SpringConfigurationPropertySource(
-				propertySource, mapper, null);
-		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("vallet");
-	}
-
 	@Test
 	public void getValueOrigin() {
 		Map<String, Object> source = new LinkedHashMap<>();

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

@@ -110,21 +110,6 @@ public class SpringIterableConfigurationPropertySourceTests {
 		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("value2");
 	}
 
-	@Test
-	public void getValueShouldUseExtractor() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("key", "value");
-		EnumerablePropertySource<?> propertySource = new MapPropertySource("test",
-				source);
-		TestPropertyMapper mapper = new TestPropertyMapper();
-		ConfigurationPropertyName name = ConfigurationPropertyName.of("my.key");
-		mapper.addFromConfigurationProperty(name, "key",
-				(value) -> value.toString().replace("ue", "let"));
-		SpringIterableConfigurationPropertySource adapter = new SpringIterableConfigurationPropertySource(
-				propertySource, mapper);
-		assertThat(adapter.getConfigurationProperty(name).getValue()).isEqualTo("vallet");
-	}
-
 	@Test
 	public void getValueOrigin() {
 		Map<String, Object> source = new LinkedHashMap<>();

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

@@ -16,16 +16,10 @@
 
 package org.springframework.boot.context.properties.source;
 
-import java.util.ArrayList;
-import java.util.LinkedHashMap;
 import java.util.List;
-import java.util.Map;
 
 import org.junit.Test;
 
-import org.springframework.core.env.MapPropertySource;
-import org.springframework.core.env.PropertySource;
-
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -50,10 +44,6 @@ public class SystemEnvironmentPropertyMapperTests extends AbstractPropertyMapper
 		assertThat(namesFromString("HOST_0_NAME")).containsExactly("host[0].name");
 		assertThat(namesFromString("HOST_F00_NAME")).containsExactly("host.f00.name");
 		assertThat(namesFromString("S-ERVER")).containsExactly("s-erver");
-		assertThat(namesFromString("SERVERS__", "1,2,3")).containsExactly("servers[0]",
-				"servers[1]", "servers[2]");
-		assertThat(namesFromString("SERVERS_0__", "1,2,3"))
-				.containsExactly("servers[0][0]", "servers[0][1]", "servers[0][2]");
 	}
 
 	@Test
@@ -69,44 +59,9 @@ public class SystemEnvironmentPropertyMapperTests extends AbstractPropertyMapper
 				"FOO_THE_BAR");
 	}
 
-	@Test
-	public void mapFromStringWhenListShortcutShouldExtractValues() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("SERVER__", "foo,bar,baz");
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		List<PropertyMapping> mappings = getMapper().map(propertySource, "SERVER__");
-		List<Object> result = new ArrayList<>();
-		for (PropertyMapping mapping : mappings) {
-			Object value = propertySource.getProperty(mapping.getPropertySourceName());
-			value = mapping.getValueExtractor().apply(value);
-			result.add(value);
-		}
-		assertThat(result).containsExactly("foo", "bar", "baz");
-	}
-
-	@Test
-	public void mapFromConfigurationShouldIncludeShortcutAndExtractValues() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		source.put("SERVER__", "foo,bar,baz");
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		List<PropertyMapping> mappings = getMapper().map(propertySource,
-				ConfigurationPropertyName.of("server[1]"));
-		List<Object> result = new ArrayList<>();
-		for (PropertyMapping mapping : mappings) {
-			Object value = propertySource.getProperty(mapping.getPropertySourceName());
-			value = mapping.getValueExtractor().apply(value);
-			if (value != null) {
-				result.add(value);
-			}
-		}
-		assertThat(result).containsExactly("bar");
-	}
-
 	@Test
 	public void underscoreShouldNotMapToEmptyString() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		List<PropertyMapping> mappings = getMapper().map(propertySource, "_");
+		List<PropertyMapping> mappings = getMapper().map("_");
 		boolean applicable = false;
 		for (PropertyMapping mapping : mappings) {
 			applicable = mapping.isApplicable(ConfigurationPropertyName.of(""));
@@ -116,9 +71,7 @@ public class SystemEnvironmentPropertyMapperTests extends AbstractPropertyMapper
 
 	@Test
 	public void underscoreWithWhitespaceShouldNotMapToEmptyString() {
-		Map<String, Object> source = new LinkedHashMap<>();
-		PropertySource<?> propertySource = new MapPropertySource("test", source);
-		List<PropertyMapping> mappings = getMapper().map(propertySource, "  _");
+		List<PropertyMapping> mappings = getMapper().map("  _");
 		boolean applicable = false;
 		for (PropertyMapping mapping : mappings) {
 			applicable = mapping.isApplicable(ConfigurationPropertyName.of(""));

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

@@ -20,7 +20,6 @@ import java.util.Collections;
 import java.util.List;
 import java.util.function.Function;
 
-import org.springframework.core.env.PropertySource;
 import org.springframework.util.LinkedMultiValueMap;
 import org.springframework.util.MultiValueMap;
 
@@ -53,13 +52,12 @@ class TestPropertyMapper implements PropertyMapper {
 	}
 
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
-			String propertySourceName) {
+	public List<PropertyMapping> map(String propertySourceName) {
 		return this.fromSource.getOrDefault(propertySourceName, Collections.emptyList());
 	}
 
 	@Override
-	public List<PropertyMapping> map(PropertySource<?> propertySource,
+	public List<PropertyMapping> map(
 			ConfigurationPropertyName configurationPropertyName) {
 		return this.fromConfig.getOrDefault(configurationPropertyName,
 				Collections.emptyList());