Fix configuration property name when group is empty

See gh-5335

spring-boot-tools/spring-boot-configuration-metadata/src/main/java/org/springframework/boot/configurationmetadata/RawConfigurationMetadata.java

@@ -77,10 +77,10 @@ class RawConfigurationMetadata {
 		}
 		ConfigurationMetadataSource source = getSource(item.getSourceType());
 		if (source != null) {
-			String groupId = source.getGroupId();
+			String dottedPrefix = source.getGroupId() + ".";
 			String id = item.getId();
-			if (id.startsWith(groupId)) { // match
-				String name = id.substring(groupId.length() + 1, id.length()); // "."
+			if (id.startsWith(dottedPrefix)) {
+				String name = id.substring(dottedPrefix.length(), id.length());
 				item.setName(name);
 			}
 		}

spring-boot-tools/spring-boot-configuration-metadata/src/test/java/org/springframework/boot/configurationmetadata/JsonReaderTests.java

 /*
- * Copyright 2012-2015 the original author or authors.
+ * Copyright 2012-2016 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.
@@ -52,6 +52,17 @@ public class JsonReaderTests extends AbstractConfigurationMetadataTests {
 		readFor("invalid");
 	}
 
+	@Test
+	public void emptyGroupName() throws IOException {
+		RawConfigurationMetadata rawMetadata = readFor("emptygroup");
+		List<ConfigurationMetadataItem> items = rawMetadata.getItems();
+		assertEquals(1, items.size());
+
+		ConfigurationMetadataItem item = items.get(0);
+		assertProperty(item, "name", "name", String.class, null);
+
+	}
+
 	@Test
 	public void simpleMetadata() throws IOException {
 		RawConfigurationMetadata rawMetadata = readFor("foo");

spring-boot-tools/spring-boot-configuration-metadata/src/test/resources/metadata/configuration-metadata-emptygroup.json

+{
+  "groups": [
+    {
+      "name": "",
+      "type": "org.acme.Foo",
+      "sourceType": "org.acme.config.FooApp",
+      "sourceMethod": "foo()",
+      "description": "This is Foo."
+    }
+  ],
+  "properties": [
+    {
+      "name": "name",
+      "type": "java.lang.String",
+      "sourceType": "org.acme.Foo"
+    }
+  ]
+}