Dump parameter names for abstract methods to a text file that FernFlower can then read as abstract methods can not have parameter names at the bytecode level.

Author: LexManos

src/main/java/de/oceanlabs/mcp/mcinjector/MCInjectorImpl.java

@@ -3,10 +3,17 @@
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.lang.reflect.Field;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.StandardOpenOption;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
 import java.util.logging.Level;
+import java.util.stream.Collectors;
 import java.util.zip.ZipEntry;
 import java.util.zip.ZipInputStream;
 import java.util.zip.ZipOutputStream;
@@ -34,6 +41,7 @@
 public class MCInjectorImpl
 {
     public LVTNaming naming = LVTNaming.STRIP;
+    private Map<String, List<String>> abstractParameters = new HashMap<>();
 
     static void process(
             Path in, Path out,
@@ -72,6 +80,7 @@ private MCInjectorImpl(){}
 
     private void processJar(Path inFile, Path outFile) throws IOException
     {
+        Set<String> entries = new HashSet<>();
         try (ZipInputStream inJar = new ZipInputStream(Files.newInputStream(inFile)))
         {
             try (ZipOutputStream outJar = new ZipOutputStream(outFile == null ? new ByteArrayOutputStream() : Files.newOutputStream(outFile, StandardOpenOption.CREATE)))
@@ -117,6 +126,19 @@ private void processJar(Path inFile, Path outFile) throws IOException
                     ZipEntry newEntry = new ZipEntry(entryName);
                     outJar.putNextEntry(newEntry);
                     outJar.write(entryData);
+                    entries.add(entryName);
+                }
+
+                if (!abstractParameters.isEmpty() && !entries.contains("fernflower_abstract_parameter_names.txt"))
+                {
+                    outJar.putNextEntry(new ZipEntry("fernflower_abstract_parameter_names.txt"));
+                    for (String key : abstractParameters.keySet().stream().sorted().collect(Collectors.toList()))
+                    {
+                        outJar.write(key.getBytes(StandardCharsets.UTF_8));//class method desc
+                        outJar.write(' ');
+                        outJar.write(abstractParameters.get(key).stream().collect(Collectors.joining(" ")).getBytes(StandardCharsets.UTF_8));
+                        outJar.write('\n');
+                    }
                 }
             }
         }
@@ -133,7 +155,7 @@ public byte[] processClass(byte[] cls, boolean readOnly)
         }
         else
         {
-            ca = new ApplyMap(ca);
+            ca = new ApplyMap(this, ca);
 
             switch (naming)
             {
@@ -220,4 +242,9 @@ public static ClassNode getClassNode(ClassVisitor cv)
 
         }
     }
+
+    public void storeAbstractParameters(String className, String name, String desc, List<String> params)
+    {
+        abstractParameters.put(className + ' ' + name  + ' ' + desc, params);
+    }
 }

src/main/java/de/oceanlabs/mcp/mcinjector/adaptors/ApplyMap.java

@@ -27,10 +27,12 @@
 public class ApplyMap extends ClassVisitor
 {
     String className;
+    MCInjectorImpl injector;
 
-    public ApplyMap(ClassVisitor cn)
+    public ApplyMap(MCInjectorImpl injector, ClassVisitor cn)
     {
         super(Opcodes.ASM6, cn);
+        this.injector = injector;
     }
 
     @Override
@@ -52,10 +54,10 @@ public MethodVisitor visitMethod(int access, String name, String desc, String si
         exceptions = processExceptions(className, name, desc, exceptions);
 
         // abstract and native methods don't have a Code attribute
-        if ((access & Opcodes.ACC_ABSTRACT) != 0 || (access & Opcodes.ACC_NATIVE) != 0)
+        /*if ((access & Opcodes.ACC_ABSTRACT) != 0 || (access & Opcodes.ACC_NATIVE) != 0)
         {
             return super.visitMethod(access, name, desc, signature, exceptions);
-        }
+        }*/
 
         return new MethodVisitor(api, cv.visitMethod(access, name, desc, signature, exceptions))
         {
@@ -121,6 +123,15 @@ else if (name.equals("<init>")) // Every constructor is given a unique ID, try t
             y += types.get(x).getSize();
         }
 
+        if ((mn.access & (Opcodes.ACC_ABSTRACT | Opcodes.ACC_NATIVE)) != 0) //Abstract and native methods dont have code so we need to store the names elseware.
+        {
+            if ((mn.access & Opcodes.ACC_STATIC) == 0)
+                params.remove(0); //remove 'this'
+            if (params.size() > 0)
+                injector.storeAbstractParameters(className, name, desc, params);
+            return;
+        }
+
         MCInjector.LOG.fine("    Applying map:");
         if (params.size() != types.size())
         {