Introduce generateCodeForArgument() in CodeFlow

Closes gh-32708

Author: sbrannen

spring-expression/src/main/java/org/springframework/expression/spel/CodeFlow.java

@@ -30,6 +30,7 @@
 import org.springframework.asm.Opcodes;
 import org.springframework.lang.Contract;
 import org.springframework.lang.Nullable;
+import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.ConcurrentReferenceHashMap;
@@ -244,6 +245,74 @@ public String getClassName() {
 		return this.className;
 	}
 
+	/**
+	 * Generate bytecode that loads the supplied argument onto the stack.
+	 * <p>Delegates to {@link #generateCodeForArgument(MethodVisitor, SpelNode, String)}
+	 * with the {@linkplain #toDescriptor(Class) descriptor} for
+	 * the supplied {@code requiredType}.
+	 * <p>This method also performs any boxing, unboxing, or check-casting
+	 * necessary to ensure that the type of the argument on the stack matches the
+	 * supplied {@code requiredType}.
+	 * <p>Use this method when a node in the AST will be used as an argument for
+	 * a constructor or method invocation. For example, if you wish to invoke a
+	 * method with an {@code indexNode} that must be of type {@code int} for the
+	 * actual method invocation within bytecode, you would call
+	 * {@code codeFlow.generateCodeForArgument(methodVisitor, indexNode, int.class)}.
+	 * @param methodVisitor the ASM {@link MethodVisitor} into which code should
+	 * be generated
+	 * @param argument a {@link SpelNode} that represents an argument to a method
+	 * or constructor
+	 * @param requiredType the required type for the argument when invoking the
+	 * corresponding constructor or method
+	 * @since 6.2
+	 * @see #generateCodeForArgument(MethodVisitor, SpelNode, String)
+	 */
+	public void generateCodeForArgument(MethodVisitor methodVisitor, SpelNode argument, Class<?> requiredType) {
+		generateCodeForArgument(methodVisitor, argument, toDescriptor(requiredType));
+	}
+
+	/**
+	 * Generate bytecode that loads the supplied argument onto the stack.
+	 * <p>This method also performs any boxing, unboxing, or check-casting
+	 * necessary to ensure that the type of the argument on the stack matches the
+	 * supplied {@code requiredTypeDesc}.
+	 * <p>Use this method when a node in the AST will be used as an argument for
+	 * a constructor or method invocation. For example, if you wish to invoke a
+	 * method with an {@code indexNode} that must be of type {@code int} for the
+	 * actual method invocation within bytecode, you would call
+	 * {@code codeFlow.generateCodeForArgument(methodVisitor, indexNode, "I")}.
+	 * @param methodVisitor the ASM {@link MethodVisitor} into which code should
+	 * be generated
+	 * @param argument a {@link SpelNode} that represents an argument to a method
+	 * or constructor
+	 * @param requiredTypeDesc a descriptor for the required type for the argument
+	 * when invoking the corresponding constructor or method
+	 * @since 6.2
+	 * @see #generateCodeForArgument(MethodVisitor, SpelNode, Class)
+	 * @see #toDescriptor(Class)
+	 */
+	public void generateCodeForArgument(MethodVisitor methodVisitor, SpelNode argument, String requiredTypeDesc) {
+		enterCompilationScope();
+		argument.generateCode(methodVisitor, this);
+		String lastDesc = lastDescriptor();
+		Assert.state(lastDesc != null, "No last descriptor");
+		boolean primitiveOnStack = isPrimitive(lastDesc);
+		// Check if we need to box it.
+		if (primitiveOnStack && requiredTypeDesc.charAt(0) == 'L') {
+			insertBoxIfNecessary(methodVisitor, lastDesc.charAt(0));
+		}
+		// Check if we need to unbox it.
+		else if (requiredTypeDesc.length() == 1 && !primitiveOnStack) {
+			insertUnboxInsns(methodVisitor, requiredTypeDesc.charAt(0), lastDesc);
+		}
+		// Check if we need to check-cast
+		else if (!requiredTypeDesc.equals(lastDesc)) {
+			// This would be unnecessary in the case of subtyping (e.g. method takes Number but Integer passed in)
+			insertCheckCast(methodVisitor, requiredTypeDesc);
+		}
+		exitCompilationScope();
+	}
+
 
 	/**
 	 * Insert any necessary cast and value call to convert from a boxed type to a

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

@@ -418,8 +418,7 @@ private void generateIndexCode(MethodVisitor mv, CodeFlow cf, SpelNodeImpl index
 	}
 
 	private void generateIndexCode(MethodVisitor mv, CodeFlow cf, SpelNodeImpl indexNode, Class<?> indexType) {
-		String indexDesc = CodeFlow.toDescriptor(indexType);
-		generateCodeForArgument(mv, cf, indexNode, indexDesc);
+		cf.generateCodeForArgument(mv, indexNode, indexType);
 	}
 
 	@Override

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

@@ -210,11 +210,11 @@ protected ValueRef getValueRef(ExpressionState state) throws EvaluationException
 
 	/**
 	 * Generate code that handles building the argument values for the specified method.
-	 * This method will take account of whether the invoked method is a varargs method
+	 * <p>This method will take into account whether the invoked method is a varargs method,
 	 * and if it is then the argument values will be appropriately packaged into an array.
 	 * @param mv the method visitor where code should be generated
 	 * @param cf the current codeflow
-	 * @param member the method or constructor for which arguments are being setup
+	 * @param member the method or constructor for which arguments are being set up
 	 * @param arguments the expression nodes for the expression supplied argument values
 	 */
 	protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Member member, SpelNodeImpl[] arguments) {
@@ -237,15 +237,15 @@ protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Me
 
 			// Fulfill all the parameter requirements except the last one
 			for (p = 0; p < paramDescriptors.length - 1; p++) {
-				generateCodeForArgument(mv, cf, arguments[p], paramDescriptors[p]);
+				cf.generateCodeForArgument(mv, arguments[p], paramDescriptors[p]);
 			}
 
 			SpelNodeImpl lastChild = (childCount == 0 ? null : arguments[childCount - 1]);
 			String arrayType = paramDescriptors[paramDescriptors.length - 1];
 			// Determine if the final passed argument is already suitably packaged in array
 			// form to be passed to the method
 			if (lastChild != null && arrayType.equals(lastChild.getExitDescriptor())) {
-				generateCodeForArgument(mv, cf, lastChild, paramDescriptors[p]);
+				cf.generateCodeForArgument(mv, lastChild, paramDescriptors[p]);
 			}
 			else {
 				arrayType = arrayType.substring(1); // trim the leading '[', may leave other '['
@@ -257,41 +257,28 @@ protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Me
 					SpelNodeImpl child = arguments[p];
 					mv.visitInsn(DUP);
 					CodeFlow.insertOptimalLoad(mv, arrayindex++);
-					generateCodeForArgument(mv, cf, child, arrayType);
+					cf.generateCodeForArgument(mv, child, arrayType);
 					CodeFlow.insertArrayStore(mv, arrayType);
 					p++;
 				}
 			}
 		}
 		else {
 			for (int i = 0; i < paramDescriptors.length;i++) {
-				generateCodeForArgument(mv, cf, arguments[i], paramDescriptors[i]);
+				cf.generateCodeForArgument(mv, arguments[i], paramDescriptors[i]);
 			}
 		}
 	}
 
 	/**
 	 * Ask an argument to generate its bytecode and then follow it up
 	 * with any boxing/unboxing/checkcasting to ensure it matches the expected parameter descriptor.
+	 * @deprecated As of Spring Framework 6.2, in favor of
+	 * {@link CodeFlow#generateCodeForArgument(MethodVisitor, SpelNode, String)}
 	 */
+	@Deprecated(since = "6.2")
 	protected static void generateCodeForArgument(MethodVisitor mv, CodeFlow cf, SpelNodeImpl argument, String paramDesc) {
-		cf.enterCompilationScope();
-		argument.generateCode(mv, cf);
-		String lastDesc = cf.lastDescriptor();
-		Assert.state(lastDesc != null, "No last descriptor");
-		boolean primitiveOnStack = CodeFlow.isPrimitive(lastDesc);
-		// Check if need to box it for the method reference?
-		if (primitiveOnStack && paramDesc.charAt(0) == 'L') {
-			CodeFlow.insertBoxIfNecessary(mv, lastDesc.charAt(0));
-		}
-		else if (paramDesc.length() == 1 && !primitiveOnStack) {
-			CodeFlow.insertUnboxInsns(mv, paramDesc.charAt(0), lastDesc);
-		}
-		else if (!paramDesc.equals(lastDesc)) {
-			// This would be unnecessary in the case of subtyping (e.g. method takes Number but Integer passed in)
-			CodeFlow.insertCheckCast(mv, paramDesc);
-		}
-		cf.exitCompilationScope();
+		cf.generateCodeForArgument(mv, argument, paramDesc);
 	}
 
 }