Propagate Map conversion failures

Align `MapBinder` with `IndexedBinder` so that if a value is specified
any converter exception are propagated.

See gh-11493

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

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -27,7 +27,6 @@ import org.springframework.boot.context.properties.source.ConfigurationPropertyS
 import org.springframework.boot.context.properties.source.IterableConfigurationPropertySource;
 import org.springframework.core.CollectionFactory;
 import org.springframework.core.ResolvableType;
-import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.util.ClassUtils;
 
 /**
@@ -58,9 +57,12 @@ class MapBinder extends AggregateBinder<Map<Object, Object>> {
 		Bindable<?> resolvedTarget = resolveTarget(target);
 		for (ConfigurationPropertySource source : getContext().getSources()) {
 			if (!ConfigurationPropertyName.EMPTY.equals(name)) {
-				Object converted = convertIfFound(name, source, resolvedTarget);
-				if (converted != null) {
-					return converted;
+				ConfigurationProperty property = source.getConfigurationProperty(name);
+				if (property != null) {
+					Object value = getContext().getPlaceholdersResolver()
+							.resolvePlaceholders(property.getValue());
+					return ResolvableTypeDescriptor.forType(target.getType())
+							.convert(getContext().getConversionService(), value);
 				}
 				source = source.filter(name::isAncestorOf);
 			}
@@ -77,20 +79,6 @@ class MapBinder extends AggregateBinder<Map<Object, Object>> {
 		return target;
 	}
 
-	private Object convertIfFound(ConfigurationPropertyName name, ConfigurationPropertySource source, Bindable<?> target) {
-		ConfigurationProperty configurationProperty = source.getConfigurationProperty(name);
-		if (configurationProperty != null) {
-			try {
-				return ResolvableTypeDescriptor.forType(target.getType())
-						.convert(getContext().getConversionService(), configurationProperty.getValue());
-			}
-			catch (ConverterNotFoundException ex) {
-
-			}
-		}
-		return null;
-	}
-
 	@Override
 	protected Map<Object, Object> merge(Map<Object, Object> existing,
 			Map<Object, Object> additional) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/properties/bind/MapBinderTests.java

 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -26,7 +26,9 @@ import java.util.Properties;
 import java.util.stream.Collectors;
 
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.mockito.Answers;
 import org.mockito.ArgumentCaptor;
 import org.mockito.InOrder;
@@ -75,6 +77,9 @@ public class MapBinderTests {
 	private static final Bindable<Map<String, String[]>> STRING_ARRAY_MAP = Bindable
 			.mapOf(String.class, String[].class);
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	private List<ConfigurationPropertySource> sources = new ArrayList<>();
 
 	private Binder binder;
@@ -532,7 +537,6 @@ public class MapBinderTests {
 		DefaultConversionService conversionService = new DefaultConversionService();
 		conversionService.addConverter(new MapConverter());
 		Binder binder = new Binder(this.sources, null, conversionService);
-
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo", "a,b");
 		this.sources.add(source);
@@ -546,8 +550,8 @@ public class MapBinderTests {
 		MockConfigurationPropertySource source = new MockConfigurationPropertySource();
 		source.put("foo", "a,b");
 		this.sources.add(source);
-		BindResult<Map<String, String>> result = this.binder.bind("foo", STRING_STRING_MAP);
-		assertThat(result.isBound()).isFalse();
+		this.thrown.expect(BindException.class);
+		this.binder.bind("foo", STRING_STRING_MAP);
 	}
 
 	private <K, V> Bindable<Map<K, V>> getMapBindable(Class<K> keyGeneric,
@@ -603,12 +607,14 @@ public class MapBinderTests {
 	}
 
 	static class MapConverter implements Converter<String, Map<String, String>> {
+
 		@Override
 		public Map<String, String> convert(String s) {
 			Map<String, String> map = new HashMap<>();
 			StringUtils.commaDelimitedListToSet(s).forEach(k -> map.put(k, ""));
 			return map;
 		}
+
 	}
 
 }