Support method arg name remapping in @ModifyVariable (#160)

* feat: ModifyVariable lvt remap

* change: allow disabling local variable tracking

* fix: checkstyle

Author: ishland

src/main/java/net/fabricmc/tinyremapper/LocalInstance.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016, 2018, Player, asie
+ * Copyright (c) 2026, FabricMC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.fabricmc.tinyremapper;
+
+import net.fabricmc.tinyremapper.api.TrLocal;
+import net.fabricmc.tinyremapper.api.TrMethod;
+
+public class LocalInstance implements TrLocal {
+	public LocalInstance(TrMethod owner, String name, String desc, int index) {
+		this.owner = owner;
+		this.name = name;
+		this.desc = desc;
+		this.index = index;
+	}
+
+	@Override
+	public String getName() {
+		return this.name;
+	}
+
+	@Override
+	public String getDesc() {
+		return this.desc;
+	}
+
+	@Override
+	public int getIndex() {
+		return this.index;
+	}
+
+	@Override
+	public TrMethod getOwner() {
+		return this.owner;
+	}
+
+	final TrMethod owner;
+	final String name;
+	final String desc;
+	final int index;
+}

src/main/java/net/fabricmc/tinyremapper/Main.java

@@ -61,6 +61,7 @@ public static void main(String[] rawArgs) {
 		boolean renameInvalidLocals = false;
 		Pattern invalidLvNamePattern = null;
 		boolean inferNameFromSameLvIndex = false;
+		boolean disableLocalVariableTracking = false;
 		NonClassCopyMode ncCopyMode = NonClassCopyMode.FIX_META_INF;
 		int threads = -1;
 
@@ -132,6 +133,9 @@ public static void main(String[] rawArgs) {
 				case "infernamefromsamelvindex":
 					inferNameFromSameLvIndex = true;
 					break;
+				case "disablelocalvariabletracking":
+					disableLocalVariableTracking = true;
+					break;
 				case "nonclasscopymode":
 					switch (arg.substring(valueSepPos + 1).toLowerCase(Locale.ENGLISH)) {
 					case "unchanged": ncCopyMode = NonClassCopyMode.UNCHANGED; break;
@@ -270,6 +274,7 @@ public static void main(String[] rawArgs) {
 				.renameInvalidLocals(renameInvalidLocals)
 				.invalidLvNamePattern(invalidLvNamePattern)
 				.inferNameFromSameLvIndex(inferNameFromSameLvIndex)
+				.disableLocalVariableTracking(disableLocalVariableTracking)
 				.threads(threads);
 
 		for (TinyRemapper.Extension ext : providedExtensions) {

src/main/java/net/fabricmc/tinyremapper/MemberInstance.java

@@ -25,6 +25,7 @@
 import net.fabricmc.tinyremapper.TinyRemapper.MrjState;
 import net.fabricmc.tinyremapper.api.TrClass;
 import net.fabricmc.tinyremapper.api.TrField;
+import net.fabricmc.tinyremapper.api.TrLocal;
 import net.fabricmc.tinyremapper.api.TrMember;
 import net.fabricmc.tinyremapper.api.TrMethod;
 
@@ -68,6 +69,11 @@ public int getIndex() {
 		return index;
 	}
 
+	@Override
+	public TrLocal[] getLocals() {
+		return this.locals.clone();
+	}
+
 	public MrjState getContext() {
 		return cls.getContext();
 	}
@@ -113,6 +119,10 @@ public void forceSetNewName(String name) {
 		newName = name;
 	}
 
+	public void setLocals(TrLocal[] locals) {
+		this.locals = locals.clone();
+	}
+
 	@Override
 	public String toString() {
 		return String.format("%s/%s%s", cls.getName(), name, desc);
@@ -151,6 +161,7 @@ public static String getNameFromId(TrMember.MemberType type, String id, boolean
 	final String desc;
 	final int access;
 	final int index;
+	TrLocal[] locals;
 	private volatile String newName;
 	private volatile String newBridgedName;
 	String newNameOriginatingCls;

src/main/java/net/fabricmc/tinyremapper/TinyRemapper.java

@@ -57,6 +57,7 @@
 import org.objectweb.asm.ClassVisitor;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.FieldVisitor;
+import org.objectweb.asm.Label;
 import org.objectweb.asm.MethodVisitor;
 import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.RecordComponentVisitor;
@@ -67,9 +68,11 @@
 import net.fabricmc.tinyremapper.IMappingProvider.Member;
 import net.fabricmc.tinyremapper.api.TrClass;
 import net.fabricmc.tinyremapper.api.TrEnvironment;
+import net.fabricmc.tinyremapper.api.TrLocal;
 import net.fabricmc.tinyremapper.api.TrLogger;
 import net.fabricmc.tinyremapper.api.TrMember;
 import net.fabricmc.tinyremapper.api.TrMember.MemberType;
+import net.fabricmc.tinyremapper.extension.mixin.common.data.Constant;
 
 public class TinyRemapper {
 	public static class Builder {
@@ -183,6 +186,14 @@ public Builder inferNameFromSameLvIndex(boolean value) {
 			return this;
 		}
 
+		/**
+		 * Whether to disable the tracking of local variable names, used in ModifyVariable local name remapping.
+		 */
+		public Builder disableLocalVariableTracking(boolean value) {
+			this.disableLocalVariableTracking = value;
+			return this;
+		}
+
 		@Deprecated
 		public Builder extraAnalyzeVisitor(ClassVisitor visitor) {
 			return extraAnalyzeVisitor((mrjVersion, className, next) -> {
@@ -233,7 +244,7 @@ public TinyRemapper build() {
 					propagateBridges, propagateRecordComponents,
 					removeFrames, ignoreConflicts, resolveMissing, checkPackageAccess || fixPackageAccess, fixPackageAccess,
 					rebuildSourceFilenames, skipLocalMapping, renameInvalidLocals, invalidLvNamePattern, inferNameFromSameLvIndex,
-					analyzeVisitors, stateProcessors, preApplyVisitors, postApplyVisitors,
+					disableLocalVariableTracking || skipLocalMapping, analyzeVisitors, stateProcessors, preApplyVisitors, postApplyVisitors,
 					extraRemapper, logger);
 
 			return remapper;
@@ -258,6 +269,7 @@ public TinyRemapper build() {
 		private boolean renameInvalidLocals = false;
 		private Pattern invalidLvNamePattern;
 		private boolean inferNameFromSameLvIndex;
+		private boolean disableLocalVariableTracking = false;
 		private final List<AnalyzeVisitorProvider> analyzeVisitors = new ArrayList<>();
 		private final List<StateProcessor> stateProcessors = new ArrayList<>();
 		private final List<ApplyVisitorProvider> preApplyVisitors = new ArrayList<>();
@@ -321,6 +333,7 @@ private TinyRemapper(Collection<IMappingProvider> mappingProviders, boolean igno
 			boolean rebuildSourceFilenames,
 			boolean skipLocalMapping,
 			boolean renameInvalidLocals, Pattern invalidLvNamePattern, boolean inferNameFromSameLvIndex,
+			boolean disableLocalVariableTracking,
 			List<AnalyzeVisitorProvider> analyzeVisitors, List<StateProcessor> stateProcessors,
 			List<ApplyVisitorProvider> preApplyVisitors, List<ApplyVisitorProvider> postApplyVisitors,
 			Remapper extraRemapper, TrLogger logger) {
@@ -345,6 +358,7 @@ private TinyRemapper(Collection<IMappingProvider> mappingProviders, boolean igno
 		this.renameInvalidLocals = renameInvalidLocals;
 		this.invalidLvNamePattern = invalidLvNamePattern;
 		this.inferNameFromSameLvIndex = inferNameFromSameLvIndex;
+		this.disableLocalVariableTracking = disableLocalVariableTracking;
 		this.analyzeVisitors = analyzeVisitors;
 		this.stateProcessors = stateProcessors;
 		this.preApplyVisitors = preApplyVisitors;
@@ -643,10 +657,29 @@ public void visit(int version, int access, String name, String signature, String
 
 			@Override
 			public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
-				MemberInstance prev = ret.addMember(new MemberInstance(TrMember.MemberType.METHOD, ret, name, desc, access, ret.getMembers().size()));
+				MemberInstance member = new MemberInstance(MemberType.METHOD, ret, name, desc, access, ret.getMembers().size());
+				MemberInstance prev = ret.addMember(member);
 				if (prev != null) throw new RuntimeException(String.format("duplicate method %s/%s%s in inputs", ret.getName(), name, desc));
 
-				return super.visitMethod(access, name, desc, signature, exceptions);
+				if (TinyRemapper.this.disableLocalVariableTracking) {
+					return super.visitMethod(access, name, desc, signature, exceptions);
+				} else {
+					return new MethodVisitor(Constant.ASM_VERSION, super.visitMethod(access, name, desc, signature, exceptions)) {
+						final List<TrLocal> locals = new ArrayList<>();
+
+						@Override
+						public void visitLocalVariable(String name, String descriptor, String signature, Label start, Label end, int index) {
+							this.locals.add(new LocalInstance(member, name, descriptor, index));
+							super.visitLocalVariable(name, descriptor, signature, start, end, index);
+						}
+
+						@Override
+						public void visitEnd() {
+							member.setLocals(locals.toArray(new TrLocal[0]));
+							super.visitEnd();
+						}
+					};
+				}
 			}
 
 			@Override
@@ -662,7 +695,11 @@ public FieldVisitor visitField(int access, String name, String desc, String sign
 			cv = analyzeVisitors.get(i).insertAnalyzeVisitor(isInput, mrjVersion, name, cv, tags);
 		}
 
-		reader.accept(cv, ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES | ClassReader.SKIP_CODE);
+		if (this.disableLocalVariableTracking) {
+			reader.accept(cv, ClassReader.SKIP_DEBUG | ClassReader.SKIP_FRAMES | ClassReader.SKIP_CODE);
+		} else {
+			reader.accept(cv, ClassReader.SKIP_FRAMES);
+		}
 
 		return ret;
 	}
@@ -1454,6 +1491,7 @@ public void propagate(TrMember m, String newName) {
 	private final boolean renameInvalidLocals;
 	private final Pattern invalidLvNamePattern;
 	private final boolean inferNameFromSameLvIndex;
+	private final boolean disableLocalVariableTracking;
 	private final List<AnalyzeVisitorProvider> analyzeVisitors;
 	private final List<StateProcessor> stateProcessors;
 	private final List<ApplyVisitorProvider> preApplyVisitors;

src/main/java/net/fabricmc/tinyremapper/api/TrLocal.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2016, 2018, Player, asie
+ * Copyright (c) 2026, FabricMC
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package net.fabricmc.tinyremapper.api;
+
+public interface TrLocal {
+	String getName();
+	String getDesc();
+	int getIndex();
+	TrMethod getOwner();
+}

src/main/java/net/fabricmc/tinyremapper/api/TrMethod.java

@@ -48,4 +48,6 @@ default boolean isAbstract() {
 	default boolean isVirtual() {
 		return getType().equals(MemberType.METHOD) && (getAccess() & (Opcodes.ACC_STATIC | Opcodes.ACC_PRIVATE)) == 0;
 	}
+
+	TrLocal[] getLocals();
 }

src/main/java/net/fabricmc/tinyremapper/extension/mixin/common/data/AnnotationElement.java

@@ -34,6 +34,7 @@ public final class AnnotationElement {
 	public static final String TO = "to";
 	public static final String SLICE = "slice";
 	public static final String METHOD = "method";
+	public static final String NAME = "name";
 	public static final String DEFINITION_METHOD = "method";
 	public static final String DEFINITION_FIELD = "field";
 }

src/main/java/net/fabricmc/tinyremapper/extension/mixin/soft/annotation/injection/CommonInjectionAnnotationVisitor.java

@@ -46,8 +46,8 @@
  * method with the first occurrence in ASM will be remapped.
  */
 class CommonInjectionAnnotationVisitor extends AnnotationVisitor {
-	private final CommonData data;
-	private final List<String> targets;
+	protected final CommonData data;
+	protected final List<String> targets;
 
 	CommonInjectionAnnotationVisitor(CommonData data, AnnotationVisitor delegate, List<String> targets) {
 		super(Constant.ASM_VERSION, Objects.requireNonNull(delegate));