IDEA-184560 Java decompiler doesn't use stored parameter names

src/org/jetbrains/java/decompiler/code/CodeConstants.java

@@ -1,4 +1,6 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+/*
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
 package org.jetbrains.java.decompiler.code;
 
 @SuppressWarnings({"unused", "SpellCheckingInspection"})
@@ -70,6 +72,7 @@ public interface CodeConstants {
   int ACC_SYNTHETIC = 0x1000;
   int ACC_ANNOTATION = 0x2000;
   int ACC_ENUM = 0x4000;
+  int ACC_MANDATED = 0x8000;
 
   // ----------------------------------------------------------------------
   // CLASS FLAGS

src/org/jetbrains/java/decompiler/main/ClassWriter.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
  */
 package org.jetbrains.java.decompiler.main;
 
@@ -697,6 +697,15 @@ public class ClassWriter {
           }
         }
 
+        List<StructMethodParametersAttribute.Entry> methodParameters = null;
+        if (DecompilerContext.getOption(IFernflowerPreferences.USE_METHOD_PARAMETERS)) {
+          StructMethodParametersAttribute attr =
+            (StructMethodParametersAttribute)mt.getAttribute(StructGeneralAttribute.ATTRIBUTE_METHOD_PARAMETERS);
+          if (attr != null) {
+            methodParameters = attr.getEntries();
+          }
+        }
+
         int index = isEnum && init ? 3 : thisVar ? 1 : 0;
         int start = isEnum && init ? 2 : 0;
         for (int i = start; i < md.params.length; i++) {
@@ -707,7 +716,10 @@ public class ClassWriter {
 
             appendParameterAnnotations(buffer, mt, paramCount);
 
-            if (methodWrapper.varproc.getVarFinal(new VarVersionPair(index, 0)) == VarTypeProcessor.VAR_EXPLICIT_FINAL) {
+            if (methodParameters != null && paramCount < methodParameters.size()) {
+              appendModifiers(buffer, methodParameters.get(paramCount).myAccessFlags, CodeConstants.ACC_FINAL, isInterface, 0);
+            }
+            else if (methodWrapper.varproc.getVarFinal(new VarVersionPair(index, 0)) == VarTypeProcessor.VAR_EXPLICIT_FINAL) {
               buffer.append("final ");
             }
 
@@ -741,7 +753,14 @@ public class ClassWriter {
             }
 
             buffer.append(' ');
-            String parameterName = methodWrapper.varproc.getVarName(new VarVersionPair(index, 0));
+
+            String parameterName;
+            if (methodParameters != null && paramCount < methodParameters.size()) {
+              parameterName = methodParameters.get(paramCount).myName;
+            }
+            else {
+              parameterName = methodWrapper.varproc.getVarName(new VarVersionPair(index, 0));
+            }
             buffer.append(parameterName == null ? "param" + index : parameterName); // null iff decompiled with errors
 
             paramCount++;

src/org/jetbrains/java/decompiler/main/extern/IFernflowerPreferences.java

@@ -1,4 +1,6 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+/*
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
 package org.jetbrains.java.decompiler.main.extern;
 
 import org.jetbrains.java.decompiler.util.InterpreterUtil;
@@ -25,6 +27,7 @@ public interface IFernflowerPreferences {
   String SYNTHETIC_NOT_SET = "nns";
   String UNDEFINED_PARAM_TYPE_OBJECT = "uto";
   String USE_DEBUG_VAR_NAMES = "udv";
+  String USE_METHOD_PARAMETERS = "ump";
   String REMOVE_EMPTY_RANGES = "rer";
   String FINALLY_DEINLINE = "fdi";
   String IDEA_NOT_NULL_ANNOTATION = "inn";
@@ -67,6 +70,7 @@ public interface IFernflowerPreferences {
     defaults.put(SYNTHETIC_NOT_SET, "0");
     defaults.put(UNDEFINED_PARAM_TYPE_OBJECT, "1");
     defaults.put(USE_DEBUG_VAR_NAMES, "1");
+    defaults.put(USE_METHOD_PARAMETERS, "1");
     defaults.put(REMOVE_EMPTY_RANGES, "1");
     defaults.put(FINALLY_DEINLINE, "1");
     defaults.put(IDEA_NOT_NULL_ANNOTATION, "1");

src/org/jetbrains/java/decompiler/struct/attr/StructGeneralAttribute.java

@@ -1,4 +1,6 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+/*
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
 package org.jetbrains.java.decompiler.struct.attr;
 
 import org.jetbrains.java.decompiler.struct.consts.ConstantPool;
@@ -33,6 +35,7 @@ public class StructGeneralAttribute {
   public static final String ATTRIBUTE_SYNTHETIC = "Synthetic";
   public static final String ATTRIBUTE_DEPRECATED = "Deprecated";
   public static final String ATTRIBUTE_LINE_NUMBER_TABLE = "LineNumberTable";
+  public static final String ATTRIBUTE_METHOD_PARAMETERS = "MethodParameters";
 
   private String name;
 
@@ -81,6 +84,9 @@ public class StructGeneralAttribute {
     else if (ATTRIBUTE_LINE_NUMBER_TABLE.equals(name)) {
       attr = new StructLineNumberTableAttribute();
     }
+    else if (ATTRIBUTE_METHOD_PARAMETERS.equals(name)) {
+      attr = new StructMethodParametersAttribute();
+    }
     else {
       // unsupported attribute
       return null;

src/org/jetbrains/java/decompiler/struct/attr/StructMethodParametersAttribute.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
+package org.jetbrains.java.decompiler.struct.attr;
+
+import org.jetbrains.java.decompiler.struct.consts.ConstantPool;
+import org.jetbrains.java.decompiler.util.DataInputFullStream;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/*
+  u1 parameters_count;
+  {   u2 name_index;
+      u2 access_flags;
+  } parameters[parameters_count];
+*/
+public class StructMethodParametersAttribute extends StructGeneralAttribute {
+  private List<Entry> myEntries;
+
+  @Override
+  public void initContent(DataInputFullStream data, ConstantPool pool) throws IOException {
+    int len = data.readUnsignedByte();
+    List<Entry> entries;
+    if (len > 0) {
+      entries = new ArrayList<>(len);
+
+      for (int i = 0; i < len; i++) {
+        int nameIndex = data.readUnsignedShort();
+        String name = nameIndex != 0 ? pool.getPrimitiveConstant(nameIndex).getString() : null;
+        int access_flags = data.readUnsignedShort();
+        entries.add(new Entry(name, access_flags));
+      }
+    }
+    else {
+      entries = Collections.emptyList();
+    }
+    myEntries = Collections.unmodifiableList(entries);
+  }
+
+  public List<Entry> getEntries() {
+    return myEntries;
+  }
+
+  public static class Entry {
+    public final String myName;
+    public final int myAccessFlags;
+
+    public Entry(String name, int accessFlags) {
+      myName = name;
+      myAccessFlags = accessFlags;
+    }
+  }
+}

test/org/jetbrains/java/decompiler/SingleClassesTest.java

@@ -1,4 +1,6 @@
-// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+/*
+ * Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+ */
 package org.jetbrains.java.decompiler;
 
 import org.jetbrains.java.decompiler.main.decompiler.ConsoleDecompiler;
@@ -45,6 +47,7 @@ public class SingleClassesTest {
   @Test public void testDeprecations() { doTest("pkg/TestDeprecations"); }
   @Test public void testExtendsList() { doTest("pkg/TestExtendsList"); }
   @Test public void testMethodParameters() { doTest("pkg/TestMethodParameters"); }
+  @Test public void testMethodParametersAttr() { doTest("pkg/TestMethodParametersAttr"); }
   @Test public void testCodeConstructs() { doTest("pkg/TestCodeConstructs"); }
   @Test public void testConstants() { doTest("pkg/TestConstants"); }
   @Test public void testEnum() { doTest("pkg/TestEnum"); }

testData/results/TestMethodParametersAttr.dec

@@ -0,0 +1,125 @@
+package decompiler;
+
+public class TestMethodParametersAttr {
+   TestMethodParametersAttr(int p01) {
+   }// 19
+
+   void m1(int p02) {
+   }// 20
+
+   static void m2(int p03) {
+   }// 21
+
+   void local() {
+      class Local {
+         Local(final int this$0) {
+         }// 36
+
+         void m(int p32) {
+         }// 37
+      }
+
+   }// 39
+
+   abstract static class C4 {
+      abstract void m1(int p51);
+
+      abstract void m2(final int p52);
+   }
+
+   abstract class C3 {
+      abstract void m1(int p51);
+
+      abstract void m2(final int p52);
+   }
+
+   interface I1 {
+      void m1(int p41);
+
+      void m2(final int p42);
+   }
+
+   static class C2 {
+      C2(int p21) {
+      }// 29
+
+      void m1(int p22) {
+      }// 30
+
+      static void m2(int p23) {
+      }// 31
+   }
+
+   class C1 {
+      C1(final int this$0) {
+      }// 24
+
+      void m(int p12) {
+      }// 25
+   }
+}
+
+class 'decompiler/TestMethodParametersAttr' {
+   method '<init> (I)V' {
+      4      4
+   }
+
+   method 'm1 (I)V' {
+      0      7
+   }
+
+   method 'm2 (I)V' {
+      0      10
+   }
+
+   method 'local ()V' {
+      0      21
+   }
+}
+
+class 'decompiler/TestMethodParametersAttr$1Local' {
+   method '<init> (Ldecompiler/TestMethodParametersAttr;I)V' {
+      9      15
+   }
+
+   method 'm (I)V' {
+      0      18
+   }
+}
+
+class 'decompiler/TestMethodParametersAttr$C2' {
+   method '<init> (I)V' {
+      4      43
+   }
+
+   method 'm1 (I)V' {
+      0      46
+   }
+
+   method 'm2 (I)V' {
+      0      49
+   }
+}
+
+class 'decompiler/TestMethodParametersAttr$C1' {
+   method '<init> (Ldecompiler/TestMethodParametersAttr;I)V' {
+      9      54
+   }
+
+   method 'm (I)V' {
+      0      57
+   }
+}
+
+Lines mapping:
+19 <-> 5
+20 <-> 8
+21 <-> 11
+24 <-> 55
+25 <-> 58
+29 <-> 44
+30 <-> 47
+31 <-> 50
+36 <-> 16
+37 <-> 19
+39 <-> 22

testData/src/pkg/TestMethodParametersAttr.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2000-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package decompiler;
+
+// compile with java 8: javap -parameters TestMethodParametersAttr.java
+public class TestMethodParametersAttr {
+  TestMethodParametersAttr(int p01) { }
+  void m1(int p02) { }
+  static void m2(int p03) { }
+
+  class C1 {
+    C1(int p11) { }
+    void m(int p12) { }
+  }
+
+  static class C2 {
+    C2(int p21) { }
+    void m1(int p22) { }
+    static void m2(int p23) { }
+  }
+
+  void local() {
+    class Local {
+      Local(int p31) { }
+      void m(int p32) { }
+    }
+  }
+
+  interface I1 {
+      void m1(int p41);
+      void m2(final int p42);
+  }
+
+  abstract class C3 {
+    abstract void m1(int p51);
+    abstract void m2(final int p52);
+  }
+
+  static abstract class C4 {
+    abstract void m1(int p51);
+    abstract void m2(final int p52);
+  }
+}