From cda577d1aacf0f90225f13050da42506f95bd2c8 Mon Sep 17 00:00:00 2001
From: Sam Brannen <104798+sbrannen@users.noreply.github.com>
Date: Tue, 23 Apr 2024 11:34:18 +0300
Subject: [PATCH] Support compilation of array and list indexing with Integer
 in SpEL

Prior to this commit, the Spring Expression Language (SpEL) failed to
compile an expression that indexed into any array or list using an
Integer.

This commit adds support for compilation of such expressions by
ensuring that an Integer is unboxed into an int in the compiled
bytecode.

See gh-32694
Closes gh-32908
---
 .../expression/spel/ast/Indexer.java          | 20 +++++++-------
 .../spel/SpelCompilationCoverageTests.java    | 26 +++++++++++++++++++
 2 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java b/spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java
index 2f6f8a922bd..e96c858c966 100644
--- a/spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java
+++ b/spring-expression/src/main/java/org/springframework/expression/spel/ast/Indexer.java
@@ -221,6 +221,8 @@ public class Indexer extends SpelNodeImpl {
 			cf.loadTarget(mv);
 		}
 
+		SpelNodeImpl index = this.children[0];
+
 		if (this.indexedType == IndexedType.ARRAY) {
 			String exitTypeDescriptor = this.exitTypeDescriptor;
 			Assert.state(exitTypeDescriptor != null, "Array not compilable without descriptor");
@@ -266,18 +268,13 @@ public class Indexer extends SpelNodeImpl {
 				}
 			};
 
-			SpelNodeImpl index = this.children[0];
-			cf.enterCompilationScope();
-			index.generateCode(mv, cf);
-			cf.exitCompilationScope();
+			generateIndexCode(mv, cf, index, int.class);
 			mv.visitInsn(insn);
 		}
 
 		else if (this.indexedType == IndexedType.LIST) {
 			mv.visitTypeInsn(CHECKCAST, "java/util/List");
-			cf.enterCompilationScope();
-			this.children[0].generateCode(mv, cf);
-			cf.exitCompilationScope();
+			generateIndexCode(mv, cf, index, int.class);
 			mv.visitMethodInsn(INVOKEINTERFACE, "java/util/List", "get", "(I)Ljava/lang/Object;", true);
 		}
 
@@ -285,13 +282,13 @@ public class Indexer extends SpelNodeImpl {
 			mv.visitTypeInsn(CHECKCAST, "java/util/Map");
 			// Special case when the key is an unquoted string literal that will be parsed as
 			// a property/field reference
-			if ((this.children[0] instanceof PropertyOrFieldReference reference)) {
+			if ((index instanceof PropertyOrFieldReference reference)) {
 				String mapKeyName = reference.getName();
 				mv.visitLdcInsn(mapKeyName);
 			}
 			else {
 				cf.enterCompilationScope();
-				this.children[0].generateCode(mv, cf);
+				index.generateCode(mv, cf);
 				cf.exitCompilationScope();
 			}
 			mv.visitMethodInsn(
@@ -328,6 +325,11 @@ public class Indexer extends SpelNodeImpl {
 		cf.pushDescriptor(this.exitTypeDescriptor);
 	}
 
+	private void generateIndexCode(MethodVisitor mv, CodeFlow cf, SpelNodeImpl indexNode, Class<?> indexType) {
+		String indexDesc = CodeFlow.toDescriptor(indexType);
+		generateCodeForArgument(mv, cf, indexNode, indexDesc);
+	}
+
 	@Override
 	public String toStringAST() {
 		return "[" + getChild(0).toStringAST() + "]";
diff --git a/spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java b/spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
index 51388a64087..4df4c4b3122 100644
--- a/spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
+++ b/spring-expression/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
@@ -671,6 +671,32 @@ public class SpelCompilationCoverageTests extends AbstractExpressionTests {
 			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/String");
 		}
 
+		@Test  // gh-32694, gh-32908
+		void indexIntoArrayUsingIntegerWrapper() {
+			context.setVariable("array", new int[] {1, 2, 3, 4});
+			context.setVariable("index", 2);
+
+			expression = parser.parseExpression("#array[#index]");
+
+			assertThat(expression.getValue(context)).isEqualTo(3);
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo(3);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("I");
+		}
+
+		@Test  // gh-32694, gh-32908
+		void indexIntoListUsingIntegerWrapper() {
+			context.setVariable("list", List.of(1, 2, 3, 4));
+			context.setVariable("index", 2);
+
+			expression = parser.parseExpression("#list[#index]");
+
+			assertThat(expression.getValue(context)).isEqualTo(3);
+			assertCanCompile(expression);
+			assertThat(expression.getValue(context)).isEqualTo(3);
+			assertThat(getAst().getExitDescriptor()).isEqualTo("Ljava/lang/Object");
+		}
+
 		private String stringify(Object object) {
 			Stream<? extends Object> stream;
 			if (object instanceof Collection<?> collection) {