Re-write of path parsing pieces of RelaxedDataBinder

Keys with explicit indexes (e.g. foo[bar]) were handled only
partially before this change and in quite a crude way. The main
new feature (or fixed bug if you prefer) is that map keys with
periods were not identified correctly, so foo[bar.spam] came out
wrong. By scanning the key for indexes "[]" first, we can split
the logic better to make sure that all keys can be explicitly
indexed if desired. I believe this would work in YAML as well
but it definitely works for properties file inputs.

Fixes gh-2387 (I believe)

spring-boot/src/main/java/org/springframework/boot/bind/RelaxedDataBinder.java

@@ -451,11 +451,26 @@ public class RelaxedDataBinder extends DataBinder {
 
 		private List<PathNode> splitPath(String path) {
 			List<PathNode> nodes = new ArrayList<PathNode>();
-			for (String name : StringUtils.delimitedListToStringArray(path, ".")) {
-				for (String sub : StringUtils.delimitedListToStringArray(name, "[")) {
-					if (StringUtils.hasText(sub)) {
-						if (sub.endsWith("]")) {
-							sub = sub.substring(0, sub.length() - 1);
+			String current = extractIndexedPaths(path, nodes);
+			for (String name : StringUtils.delimitedListToStringArray(current, ".")) {
+				if (StringUtils.hasText(name)) {
+					nodes.add(new PropertyNode(name));
+				}
+			}
+			return nodes;
+		}
+
+		private String extractIndexedPaths(String path, List<PathNode> nodes) {
+			int begin = 0;
+			int startRef = path.indexOf("[");
+			String current = path;
+			while (startRef >= 0) {
+				if (startRef > begin) {
+					nodes.addAll(splitPath(current.substring(begin, startRef)));
+				}
+				int endRef = current.indexOf("]", startRef);
+				if (endRef > 0) {
+					String sub = current.substring(startRef + 1, endRef);
 					if (sub.matches("[0-9]+")) {
 						nodes.add(new ArrayIndexNode(sub));
 					}
@@ -463,13 +478,11 @@ public class RelaxedDataBinder extends DataBinder {
 						nodes.add(new MapIndexNode(sub));
 					}
 				}
-						else {
-							nodes.add(new PropertyNode(sub));
-						}
-					}
+				begin = endRef + 1;
+				current = current.substring(begin);
+				startRef = current.indexOf("[");
 			}
-			}
-			return nodes;
+			return current;
 		}
 
 		public void collapseKeys(int index) {

spring-boot/src/test/java/org/springframework/boot/bind/RelaxedDataBinderTests.java

@@ -301,6 +301,14 @@ public class RelaxedDataBinderTests {
 		assertEquals("123", target.getNested().get("value.foo"));
 	}
 
+	@Test
+	public void testBindNestedMapOfStringReferenced() throws Exception {
+		TargetWithNestedMapOfString target = new TargetWithNestedMapOfString();
+		bind(target, "nested.foo: bar\n" + "nested[value.foo]: 123");
+		assertEquals("bar", target.getNested().get("foo"));
+		assertEquals("123", target.getNested().get("value.foo"));
+	}
+
 	@Test
 	public void testBindNestedMapOfEnum() throws Exception {
 		this.conversionService = new DefaultConversionService();
@@ -317,6 +325,13 @@ public class RelaxedDataBinderTests {
 		assertEquals("123", target.getNested().get("value"));
 	}
 
+	@Test
+	public void testBindNestedMapBracketReferencedAndPeriods() throws Exception {
+		TargetWithNestedMap target = new TargetWithNestedMap();
+		bind(target, "nested[foo]: bar\n" + "nested[foo.value]: 123");
+		assertEquals("123", target.getNested().get("foo.value"));
+	}
+
 	@SuppressWarnings("unchecked")
 	@Test
 	public void testBindDoubleNestedMap() throws Exception {