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Revise compilation support in SpEL for varargs array subtypes
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This commit first reverts changes to SpelNodeImpl from the previous
commit in order to reduce the scope of the overall change set.

This commit then implements a different approach to support type-safe
checks for array subtype compatibility.

In order to support backward compatibility, this commit also
reintroduces generateCodeForArguments(MethodVisitor, CodeFlow, Member,
SpelNodeImpl[]) in deprecated form.

See gh-32804
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@sbrannen
sbrannen committed May 14, 2024
1 parent 12727a2 commit 8fe4493
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Showing 2 changed files with 79 additions and 43 deletions.
107 changes: 70 additions & 37 deletions spring-expression/src/main/java/org/springframework/expression/spel/ast/SpelNodeImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,11 +17,12 @@
package org.springframework.expression.spel.ast;

import java.lang.reflect.Executable;
import java.util.Objects;
import java.lang.reflect.Member;
import java.util.function.Supplier;

import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Opcodes;
import org.springframework.asm.Type;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypedValue;
import org.springframework.expression.common.ExpressionUtils;
Expand All @@ -32,7 +33,9 @@
import org.springframework.expression.spel.SpelNode;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;

/**
* The common supertype of all AST nodes in a parsed Spring Expression Language
Expand Down Expand Up @@ -213,65 +216,95 @@ protected ValueRef getValueRef(ExpressionState state) throws EvaluationException
* 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 executable the method or constructor for which arguments are being set up
* @param member the method or constructor for which arguments are being set up
* @param arguments the expression nodes for the expression supplied argument values
* @deprecated As of Spring Framework 6.2, in favor of
* {@link #generateCodeForArguments(MethodVisitor, CodeFlow, Executable, SpelNodeImpl[])}
*/
@Deprecated(since = "6.2")
protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Member member, SpelNodeImpl[] arguments) {
if (member instanceof Executable executable) {
generateCodeForArguments(mv, cf, executable, arguments);
}
throw new IllegalArgumentException(
"The supplied member must be an instance of java.lang.reflect.Executable: " + member);
}

/**
* Generate code that handles building the argument values for the specified
* {@link Executable} (method or constructor).
* <p>This method takes into account whether the invoked executable was
* declared to accept varargs, and if it was 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 {@link CodeFlow}
* @param executable the {@link Executable} (method or constructor) for which
* arguments are being set up
* @param arguments the expression nodes for the expression supplied argument
* values
* @since 6.2
*/
protected static void generateCodeForArguments(MethodVisitor mv, CodeFlow cf, Executable executable, SpelNodeImpl[] arguments) {
String[] paramDescriptors = CodeFlow.toDescriptors(executable.getParameterTypes());
int paramCount = paramDescriptors.length;
Class<?>[] parameterTypes = executable.getParameterTypes();
String[] paramDescriptors = CodeFlow.toDescriptors(parameterTypes);

if (executable.isVarArgs()) {
// The final parameter may or may not need packaging into an array, or nothing may
// have been passed to satisfy the varargs and so something needs to be built.
int p = 0; // Current supplied argument being processed
int childCount = arguments.length;

// Fulfill all the parameter requirements except the last one
for (int i = 0; i < paramCount - 1; i++) {
cf.generateCodeForArgument(mv, arguments[i], paramDescriptors[i]);
for (p = 0; p < paramDescriptors.length - 1; p++) {
cf.generateCodeForArgument(mv, arguments[p], paramDescriptors[p]);
}

int argCount = arguments.length;
String varargsType = paramDescriptors[paramCount - 1];
String varargsComponentType = varargsType.substring(1); // trim the leading '[', may leave other '['
SpelNodeImpl lastChild = (childCount == 0 ? null : arguments[childCount - 1]);
ClassLoader classLoader = executable.getDeclaringClass().getClassLoader();
Class<?> lastChildType = (lastChild != null ?
loadClassForExitDescriptor(lastChild.getExitDescriptor(), classLoader) : null);
Class<?> lastParameterType = parameterTypes[parameterTypes.length - 1];

if (needsVarargsArrayWrapping(arguments, paramDescriptors)) {
// Package up the remaining arguments into an array
CodeFlow.insertNewArrayCode(mv, argCount - paramCount + 1, varargsComponentType);
for (int argIndex = paramCount - 1, arrayIndex = 0; argIndex < argCount; argIndex++, arrayIndex++) {
SpelNodeImpl child = arguments[argIndex];
mv.visitInsn(DUP);
CodeFlow.insertOptimalLoad(mv, arrayIndex);
cf.generateCodeForArgument(mv, child, varargsComponentType);
CodeFlow.insertArrayStore(mv, varargsComponentType);
}
}
else if (varargsType.equals(arguments[argCount - 1].getExitDescriptor())) {
// varargs type matches type of last argument
cf.generateCodeForArgument(mv, arguments[argCount - 1], paramDescriptors[paramCount - 1]);
// Determine if the final passed argument is already suitably packaged in array
// form to be passed to the method
if (lastChild != null && lastChildType != null && lastParameterType.isAssignableFrom(lastChildType)) {
cf.generateCodeForArgument(mv, lastChild, paramDescriptors[p]);
}
else {
// last argument is an array and varargs component type is a supertype of argument component type
cf.generateCodeForArgument(mv, arguments[argCount - 1], varargsComponentType);
String arrayType = paramDescriptors[paramDescriptors.length - 1];
arrayType = arrayType.substring(1); // trim the leading '[', may leave other '['
// build array big enough to hold remaining arguments
CodeFlow.insertNewArrayCode(mv, childCount - p, arrayType);
// Package up the remaining arguments into the array
int arrayindex = 0;
while (p < childCount) {
SpelNodeImpl child = arguments[p];
mv.visitInsn(DUP);
CodeFlow.insertOptimalLoad(mv, arrayindex++);
cf.generateCodeForArgument(mv, child, arrayType);
CodeFlow.insertArrayStore(mv, arrayType);
p++;
}
}
}
else {
for (int i = 0; i < paramCount; i++) {
for (int i = 0; i < paramDescriptors.length;i++) {
cf.generateCodeForArgument(mv, arguments[i], paramDescriptors[i]);
}
}
}

private static boolean needsVarargsArrayWrapping(SpelNodeImpl[] arguments, String[] paramDescriptors) {
if (arguments.length == 0) {
return true;
@Nullable
private static Class<?> loadClassForExitDescriptor(@Nullable String exitDescriptor, ClassLoader classLoader) {
if (!StringUtils.hasText(exitDescriptor)) {
return null;
}

String lastExitTypeDescriptor = arguments[arguments.length - 1].exitTypeDescriptor;
String lastParamDescriptor = paramDescriptors[paramDescriptors.length - 1];
return countLeadingOpeningBrackets(Objects.requireNonNull(lastExitTypeDescriptor)) != countLeadingOpeningBrackets(lastParamDescriptor);
}

private static long countLeadingOpeningBrackets(String lastExitTypeDescriptor) {
return lastExitTypeDescriptor.chars().takeWhile(c -> c == '[').count();
String typeDescriptor = exitDescriptor;
if (typeDescriptor.startsWith("[") || typeDescriptor.startsWith("L")) {
typeDescriptor += ";";
}
String className = Type.getType(typeDescriptor).getClassName();
return ClassUtils.resolveClassName(className, classLoader);
}

/**
Expand Down
15 changes: 9 additions & 6 deletions ...ssion/src/test/java/org/springframework/expression/spel/SpelCompilationCoverageTests.java
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Original file line number Diff line number Diff line change
Expand Up @@ -4920,19 +4920,22 @@ void constructorReference() {
// varargs
expression = parser.parseExpression("new " + testclass8 + "(#root)");
Object[] objectArray = { "a", "b", "c" };
assertThat(expression.getValue(objectArray).getClass().getName()).isEqualTo(testclass8);
o = expression.getValue(objectArray);
assertThat(o).isExactlyInstanceOf(TestClass8.class);
assertCanCompile(expression);
o = expression.getValue(objectArray);
assertThat(o.getClass().getName()).isEqualTo(testclass8);
assertThat(o).isExactlyInstanceOf(TestClass8.class);
tc8 = (TestClass8) o;
assertThat(tc8.args).containsExactly("a", "b", "c");

// varargs with argument component type that is a subtype of the varargs component type.
expression = parser.parseExpression("new " + testclass8 + "(#root)");
assertThat(expression.getValue(objectArray).getClass().getName()).isEqualTo(testclass8);
String[] stringArray = { "a", "b", "c" };
o = expression.getValue(stringArray);
assertThat(o).isExactlyInstanceOf(TestClass8.class);
assertCanCompile(expression);
o = expression.getValue(new String[] { "a", "b", "c" });
assertThat(o.getClass().getName()).isEqualTo(testclass8);
o = expression.getValue(stringArray);
assertThat(o).isExactlyInstanceOf(TestClass8.class);
tc8 = (TestClass8) o;
assertThat(tc8.args).containsExactly("a", "b", "c");

Expand Down Expand Up @@ -6939,7 +6942,7 @@ public void eighteen(String a, Object... vargs) {
s = a + "::";
}
else {
s = a+"::";
s = a + "::";
for (Object varg: vargs) {
s += varg;
}
Expand Down

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