Removes bytecode references to `java.lang.invoke.MethodHandles.Lookup…

…` on Java 6 and older

Fixes #61

README.md

@@ -214,6 +214,9 @@ Version History
   ([Issue #56](https://github.com/orfjackal/retrolambda/issues/56))
 - Fixed method references to constructors of the current class
   ([Issue #60](https://github.com/orfjackal/retrolambda/issues/60))
+- Removes bytecode references to `java.lang.invoke.MethodHandles.Lookup` on
+  Java 6 and older
+  ([Issue #61](https://github.com/orfjackal/retrolambda/issues/61))
 
 ### Retrolambda 2.0.3 (2015-06-07)
 

end-to-end-tests/end-to-end-tests.iml

@@ -14,6 +14,7 @@
     <orderEntry type="library" name="Maven: com.google.guava:guava:11.0.2" level="project" />
     <orderEntry type="library" name="Maven: com.google.code.findbugs:jsr305:1.3.9" level="project" />
     <orderEntry type="library" scope="TEST" name="Maven: commons-lang:commons-lang:2.6" level="project" />
+    <orderEntry type="library" scope="TEST" name="Maven: org.ow2.asm:asm-debug-all:5.0.4" level="project" />
     <orderEntry type="module-library">
       <library name="Maven: net.orfjackal.retrolambda:java-lang-dummies:1">
         <CLASSES>

end-to-end-tests/pom.xml

@@ -28,6 +28,12 @@
             <scope>test</scope>
         </dependency>
 
+        <dependency>
+            <groupId>org.ow2.asm</groupId>
+            <artifactId>asm-debug-all</artifactId>
+            <scope>test</scope>
+        </dependency>
+
         <!-- See net.orfjackal.retrolambda.test.ClasspathTest#ignores_classes_in_explicit_classpath_that_are_under_the_java_package -->
         <dependency>
             <groupId>net.orfjackal.retrolambda</groupId>

end-to-end-tests/src/test/java/net/orfjackal/retrolambda/test/LambdaTest.java

@@ -4,15 +4,20 @@
 
 package net.orfjackal.retrolambda.test;
 
+import org.apache.commons.lang.SystemUtils;
 import org.junit.Test;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.tree.*;
 
+import java.io.IOException;
 import java.lang.reflect.*;
 import java.util.*;
 import java.util.concurrent.Callable;
 
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.assertTrue;
+import static org.junit.Assume.assumeThat;
 
 public class LambdaTest extends SuperClass {
 
@@ -260,6 +265,19 @@ Callable<String> childRef() {
         assertThat(((Parent) child).privateMethod(), is("parent version"));
         assertThat(child.parentRef().call(), is("parent version"));
     }
+
+    @Test
+    public void bytecode_will_not_contain_dangling_references_to_MethodHandles() throws IOException {
+        assumeThat(SystemUtils.JAVA_VERSION_FLOAT, is(lessThan(1.7f)));
+
+        ClassReader cr = new ClassReader(getClass().getName().replace('.', '/'));
+        ClassNode cn = new ClassNode();
+        cr.accept(cn, ClassReader.SKIP_CODE);
+
+        for (InnerClassNode innerClass : cn.innerClasses) {
+            assertThat(innerClass.name, not(startsWith("java/lang/invoke")));
+        }
+    }
 }
 
 class SuperClass {

parent/pom.xml

@@ -47,6 +47,8 @@
         <testBytecodeTarget>1.7</testBytecodeTarget>
         <testFork>false</testFork>
         <testDefaultMethods>true</testDefaultMethods>
+        <!-- Override the default value of this property, but allow changing it on the command line -->
+        <maven.test.redirectTestOutputToFile>true</maven.test.redirectTestOutputToFile>
     </properties>
 
     <prerequisites>
@@ -167,7 +169,7 @@
                     <includes>
                         <include>**/*Test.class</include>
                     </includes>
-                    <redirectTestOutputToFile>true</redirectTestOutputToFile>
+                    <redirectTestOutputToFile>${maven.test.redirectTestOutputToFile}</redirectTestOutputToFile>
                 </configuration>
             </plugin>
 
@@ -177,7 +179,7 @@
                     <includes>
                         <include>**/*Test.class</include>
                     </includes>
-                    <redirectTestOutputToFile>true</redirectTestOutputToFile>
+                    <redirectTestOutputToFile>${maven.test.redirectTestOutputToFile}</redirectTestOutputToFile>
                     <jvm>${testJavaHome}/bin/java</jvm>
                 </configuration>
             </plugin>

retrolambda/src/main/java/net/orfjackal/retrolambda/Transformers.java

@@ -113,6 +113,7 @@ private byte[] transform(Consumer<ClassVisitor> reader, ClassVisitorChain chain)
         next = new LowerBytecodeVersion(next, targetVersion);
         if (targetVersion < Opcodes.V1_7) {
             next = new SwallowSuppressedExceptions(next);
+            next = new RemoveMethodHandlesLookupReferences(next);
         }
         next = new FixInvokeStaticOnInterfaceMethod(next);
         next = chain.wrap(next);

retrolambda/src/main/java/net/orfjackal/retrolambda/lambdas/RemoveMethodHandlesLookupReferences.java

@@ -0,0 +1,27 @@
+// Copyright © 2013-2015 Esko Luontola <www.orfjackal.net>
+// This software is released under the Apache License 2.0.
+// The license text is at http://www.apache.org/licenses/LICENSE-2.0
+
+package net.orfjackal.retrolambda.lambdas;
+
+import org.objectweb.asm.*;
+
+import java.lang.invoke.MethodHandles;
+
+import static org.objectweb.asm.Opcodes.ASM5;
+
+public class RemoveMethodHandlesLookupReferences extends ClassVisitor {
+
+    private static final String METHOD_HANDLES_LOOKUP = Type.getType(MethodHandles.Lookup.class).getInternalName();
+
+    public RemoveMethodHandlesLookupReferences(ClassVisitor next) {
+        super(ASM5, next);
+    }
+
+    @Override
+    public void visitInnerClass(String name, String outerName, String innerName, int access) {
+        if (!name.equals(METHOD_HANDLES_LOOKUP)) {
+            super.visitInnerClass(name, outerName, innerName, access);
+        }
+    }
+}