Address TODOs in SpEL's Indexer

This commit deletes outdated TODOs and addresses a remaining "current"
TODO in SpEL's Indexer.

spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java

@@ -24,7 +24,6 @@ import java.lang.reflect.Modifier;
 import java.util.Collection;
 import java.util.List;
 import java.util.Map;
-import java.util.StringJoiner;
 import java.util.function.Supplier;
 
 import org.springframework.asm.MethodVisitor;
@@ -54,8 +53,6 @@ import org.springframework.util.ReflectionUtils;
  * @author Sam Brannen
  * @since 3.0
  */
-// TODO support multidimensional arrays
-// TODO support correct syntax for multidimensional [][][] and not [,,,]
 public class Indexer extends SpelNodeImpl {
 
 	private enum IndexedType {ARRAY, LIST, MAP, STRING, OBJECT}
@@ -185,7 +182,6 @@ public class Indexer extends SpelNodeImpl {
 		}
 
 		// Try and treat the index value as a property of the context object
-		// TODO Could call the conversion service to convert the value to a String
 		TypeDescriptor valueType = indexValue.getTypeDescriptor();
 		if (valueType != null && String.class == valueType.getType()) {
 			this.indexedType = IndexedType.OBJECT;
@@ -209,7 +205,7 @@ public class Indexer extends SpelNodeImpl {
 			return (this.children[0] instanceof PropertyOrFieldReference || this.children[0].isCompilable());
 		}
 		else if (this.indexedType == IndexedType.OBJECT) {
-			// If the string name is changing the accessor is clearly going to change (so no compilation possible)
+			// If the string name is changing, the accessor is clearly going to change (so no compilation possible)
 			return (this.cachedReadAccessor != null &&
 					this.cachedReadAccessor instanceof ReflectivePropertyAccessor.OptimalPropertyAccessor &&
 					getChild(0) instanceof StringLiteral);
@@ -326,12 +322,7 @@ public class Indexer extends SpelNodeImpl {
 
 	@Override
 	public String toStringAST() {
-		// TODO Since we do not support multidimensional arrays, we should be able to return: "[" + getChild(0).toStringAST() + "]"
-		StringJoiner sj = new StringJoiner(",", "[", "]");
-		for (int i = 0; i < getChildCount(); i++) {
-			sj.add(getChild(i).toStringAST());
-		}
-		return sj.toString();
+		return "[" + getChild(0).toStringAST() + "]";
 	}
 
 

spring-expression/src/test/java/org/springframework/expression/spel/IndexingTests.java

@@ -44,6 +44,25 @@ import static org.springframework.expression.spel.SpelMessage.UNABLE_TO_GROW_COL
 @SuppressWarnings("rawtypes")
 class IndexingTests {
 
+	@Test
+	@SuppressWarnings("unchecked")
+	void indexIntoArrays() {
+		SpelExpressionParser parser = new SpelExpressionParser();
+
+		// One-dimensional
+		this.property = new int[] {1, 2, 3, 4};
+		Expression expression = parser.parseExpression("property[2]");
+		assertThat(expression.getValue(this)).isEqualTo(3);
+
+		// Multi-dimensional
+		this.property = new int[][] {{1, 2}, {3, 4}};
+		expression = parser.parseExpression("property[0]");
+		assertThat(expression.getValue(this)).isEqualTo(new int[] {1, 2});
+		expression = parser.parseExpression("property[1][1]");
+		assertThat(expression.getValue(this)).isEqualTo(4);
+	}
+
+
 	@Test
 	@SuppressWarnings("unchecked")
 	void indexIntoGenericPropertyContainingMap() {