Fix merge conflicts

Signed-off-by: shedaniel <daniel@shedaniel.me>

11 files changed, 347 insertions, 44 deletions

diff --git a/src/main/java/net/fabricmc/loom/LoomGradlePlugin.java b/src/main/java/net/fabricmc/loom/LoomGradlePlugin.java
index cf0b5424..b9876788 100644
--- a/src/main/java/net/fabricmc/loom/LoomGradlePlugin.java
+++ b/src/main/java/net/fabricmc/loom/LoomGradlePlugin.java
@@ -74,7 +74,7 @@ public class LoomGradlePlugin implements BootstrappedPlugin {
 			project.getLogger().lifecycle("You are using an unstable version of Architectury Loom! Please report any issues found!");
 		}
 
-		refreshDeps = project.getGradle().getStartParameter().isRefreshDependencies() || "true".equals(System.getProperty("loom.refresh"));
+		refreshDeps = project.getGradle().getStartParameter().isRefreshDependencies() || Boolean.getBoolean("loom.refresh");
 
 		if (refreshDeps) {
 			project.getLogger().lifecycle("Refresh dependencies is in use, loom will be significantly slower.");
diff --git a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
index a93d97c1..ffd4e9ce 100644
--- a/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
+++ b/src/main/java/net/fabricmc/loom/api/mappings/layered/spec/LayeredMappingSpecBuilder.java
@@ -49,4 +49,10 @@ public interface LayeredMappingSpecBuilder {
 	LayeredMappingSpecBuilder parchment(Object object, Action<ParchmentMappingsSpecBuilder> action);
 
 	LayeredMappingSpecBuilder crane(Object object);
+
+	/**
+	 * Add a signatureFix layer. Reads the @extras/record_signatures.json" file in a jar file such as yarn.
+	 */
+	@ApiStatus.Experimental
+	LayeredMappingSpecBuilder signatureFix(Object object);
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
index ce9172b8..6987ea5b 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingSpecBuilderImpl.java
@@ -37,6 +37,7 @@ import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
 import net.fabricmc.loom.api.mappings.layered.spec.ParchmentMappingsSpecBuilder;
 import net.fabricmc.loom.api.LoomGradleExtensionAPI;
 import net.fabricmc.loom.configuration.providers.mappings.crane.CraneMappingsSpec;
+import net.fabricmc.loom.configuration.providers.mappings.extras.signatures.SignatureFixesSpec;
 import net.fabricmc.loom.configuration.providers.mappings.intermediary.IntermediaryMappingsSpec;
 import net.fabricmc.loom.configuration.providers.mappings.mojmap.MojangMappingsSpec;
 import net.fabricmc.loom.configuration.providers.mappings.parchment.ParchmentMappingsSpecBuilderImpl;
@@ -75,6 +76,11 @@ public class LayeredMappingSpecBuilderImpl implements LayeredMappingSpecBuilder
 		return this;
 	}
 
+	@Override
+	public LayeredMappingSpecBuilder signatureFix(Object object) {
+		return addLayer(new SignatureFixesSpec(FileSpec.create(object)));
+	}
+
 	public LayeredMappingSpec build() {
 		List<MappingsSpec<?>> builtLayers = new LinkedList<>();
 		// Intermediary is always the base layer
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
index 84c9370d..21f1d2fd 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsDependency.java
@@ -32,6 +32,8 @@ import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.Collections;
+import java.util.List;
+import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
 
@@ -55,6 +57,7 @@ import org.zeroturnaround.zip.ZipUtil;
 
 import net.fabricmc.loom.LoomGradlePlugin;
 import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.mappingio.adapter.MappingDstNsReorder;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
@@ -84,29 +87,51 @@ public class LayeredMappingsDependency extends AbstractModuleDependency implemen
 		if (!Files.exists(mappingsFile) || LoomGradlePlugin.refreshDeps) {
 			try {
 				var processor = new LayeredMappingsProcessor(layeredMappingSpec);
-				MemoryMappingTree mappings = processor.getMappings(mappingContext);
+				List<MappingLayer> layers = processor.resolveLayers(mappingContext);
 
-				try (Writer writer = new StringWriter()) {
-					Tiny2Writer tiny2Writer = new Tiny2Writer(writer, false);
+				Files.deleteIfExists(mappingsFile);
 
-					MappingDstNsReorder nsReorder = new MappingDstNsReorder(tiny2Writer, Collections.singletonList(MappingsNamespace.NAMED.toString()));
-					MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(nsReorder, MappingsNamespace.INTERMEDIARY.toString(), true);
-					mappings.accept(nsSwitch);
-
-					Files.deleteIfExists(mappingsFile);
-
-					ZipUtil.pack(new ZipEntrySource[] {
-							new ByteSource("mappings/mappings.tiny", writer.toString().getBytes(StandardCharsets.UTF_8))
-					}, mappingsFile.toFile());
-				}
+				writeMapping(processor, layers, mappingsFile);
+				writeSignatureFixes(processor, layers, mappingsFile);
 			} catch (IOException e) {
-				throw new RuntimeException("Failed to resolve Mojang mappings", e);
+				throw new RuntimeException("Failed to resolve layered mappings", e);
 			}
 		}
 
 		return Collections.singleton(mappingsFile.toFile());
 	}
 
+	private void writeMapping(LayeredMappingsProcessor processor, List<MappingLayer> layers, Path mappingsFile) throws IOException {
+		MemoryMappingTree mappings = processor.getMappings(layers);
+
+		try (Writer writer = new StringWriter()) {
+			Tiny2Writer tiny2Writer = new Tiny2Writer(writer, false);
+
+			MappingDstNsReorder nsReorder = new MappingDstNsReorder(tiny2Writer, Collections.singletonList(MappingsNamespace.NAMED.toString()));
+			MappingSourceNsSwitch nsSwitch = new MappingSourceNsSwitch(nsReorder, MappingsNamespace.INTERMEDIARY.toString(), true);
+			mappings.accept(nsSwitch);
+
+			ZipUtil.pack(new ZipEntrySource[] {
+					new ByteSource("mappings/mappings.tiny", writer.toString().getBytes(StandardCharsets.UTF_8))
+			}, mappingsFile.toFile());
+		}
+	}
+
+	private void writeSignatureFixes(LayeredMappingsProcessor processor, List<MappingLayer> layers, Path mappingsFile) throws IOException {
+		Map<String, String> signatureFixes = processor.getSignatureFixes(layers);
+
+		if (signatureFixes == null) {
+			return;
+		}
+
+		byte[] data = LoomGradlePlugin.OBJECT_MAPPER.writeValueAsString(signatureFixes).getBytes(StandardCharsets.UTF_8);
+
+		ZipUtil.addEntry(
+				mappingsFile.toFile(),
+				new ByteSource("extras/record_signatures.json", data)
+		);
+	}
+
 	@Override
 	public Set<File> resolve(boolean transitive) {
 		return resolve();
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
index b14902c5..f2edfb2b 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/LayeredMappingsProcessor.java
@@ -26,12 +26,19 @@ package net.fabricmc.loom.configuration.providers.mappings;
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
+
+import org.jetbrains.annotations.Nullable;
 
 import net.fabricmc.loom.api.mappings.layered.MappingContext;
 import net.fabricmc.loom.api.mappings.layered.MappingLayer;
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
+import net.fabricmc.loom.configuration.providers.mappings.extras.signatures.SignatureFixesLayer;
 import net.fabricmc.mappingio.adapter.MappingSourceNsSwitch;
 import net.fabricmc.mappingio.tree.MemoryMappingTree;
 
@@ -42,9 +49,8 @@ public class LayeredMappingsProcessor {
 		this.layeredMappingSpec = spec;
 	}
 
-	public MemoryMappingTree getMappings(MappingContext context) throws IOException {
-		MemoryMappingTree mappingTree = new MemoryMappingTree();
-
+	public List<MappingLayer> resolveLayers(MappingContext context) {
+		List<MappingLayer> layers = new LinkedList<>();
 		List<Class<? extends MappingLayer>> visitedLayers = new ArrayList<>();
 
 		for (MappingsSpec<?> spec : layeredMappingSpec.layers()) {
@@ -56,8 +62,17 @@ public class LayeredMappingsProcessor {
 				}
 			}
 
+			layers.add(layer);
 			visitedLayers.add(layer.getClass());
+		}
+
+		return Collections.unmodifiableList(layers);
+	}
+
+	public MemoryMappingTree getMappings(List<MappingLayer> layers) throws IOException {
+		MemoryMappingTree mappingTree = new MemoryMappingTree();
 
+		for (MappingLayer layer : layers) {
 			// We have to rebuild a new tree to work on when a layer doesnt merge into layered
 			boolean rebuild = layer.getSourceNamespace() != MappingsNamespace.NAMED;
 			MemoryMappingTree workingTree;
@@ -90,4 +105,21 @@ public class LayeredMappingsProcessor {
 
 		return mappingTree;
 	}
+
+	@Nullable
+	public Map<String, String> getSignatureFixes(List<MappingLayer> layers) {
+		Map<String, String> signatureFixes = new HashMap<>();
+
+		for (MappingLayer layer : layers) {
+			if (layer instanceof SignatureFixesLayer signatureFixesLayer) {
+				signatureFixes.putAll(signatureFixesLayer.getSignatureFixes());
+			}
+		}
+
+		if (signatureFixes.isEmpty()) {
+			return null;
+		}
+
+		return Collections.unmodifiableMap(signatureFixes);
+	}
 }
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
index 8adfc28b..add9af99 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/MappingsProviderImpl.java
@@ -27,6 +27,7 @@ package net.fabricmc.loom.configuration.providers.mappings;
 import java.io.BufferedReader;
 import java.io.File;
 import java.io.IOException;
+import java.io.Reader;
 import java.io.UncheckedIOException;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
@@ -41,6 +42,7 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Objects;
+import java.util.Map;
 import java.util.function.Consumer;
 import java.util.regex.Pattern;
 
@@ -50,6 +52,7 @@ import com.google.gson.JsonObject;
 import org.apache.tools.ant.util.StringUtils;
 import org.gradle.api.Project;
 import org.gradle.api.artifacts.Configuration;
+import org.jetbrains.annotations.Nullable;
 import org.zeroturnaround.zip.FileSource;
 import org.zeroturnaround.zip.ZipEntrySource;
 import org.zeroturnaround.zip.ZipUtil;
@@ -109,6 +112,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 	private UnpickMetadata unpickMetadata;
 	private MemoryMappingTree mappingTree;
 	private MemoryMappingTree mappingTreeWithSrg;
+	private Map<String, String> signatureFixes;
 
 	public MappingsProviderImpl(Project project) {
 		super(project);
@@ -141,7 +145,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			storeMappings(getProject(), minecraftProvider, mappingsJar.toPath(), postPopulationScheduler);
 		} else {
 			try (FileSystem fileSystem = FileSystems.newFileSystem(mappingsJar.toPath(), (ClassLoader) null)) {
-				extractUnpickDefinitions(fileSystem, unpickDefinitions);
+				extractExtras(fileSystem);
 			}
 		}
 
@@ -299,7 +303,7 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 
 		try (FileSystem fileSystem = FileSystems.newFileSystem(yarnJar, (ClassLoader) null)) {
 			extractMappings(fileSystem, baseTinyMappings);
-			extractUnpickDefinitions(fileSystem, unpickDefinitions);
+			extractExtras(fileSystem);
 		}
 
 		if (areMappingsMergedV2(baseTinyMappings)) {
@@ -388,7 +392,12 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 		Files.copy(jar.getPath("mappings/mappings.tiny"), extractTo, StandardCopyOption.REPLACE_EXISTING);
 	}
 
-	private void extractUnpickDefinitions(FileSystem jar, Path extractTo) throws IOException {
+	private void extractExtras(FileSystem jar) throws IOException {
+		extractUnpickDefinitions(jar);
+		extractSignatureFixes(jar);
+	}
+
+	private void extractUnpickDefinitions(FileSystem jar) throws IOException {
 		Path unpickPath = jar.getPath("extras/definitions.unpick");
 		Path unpickMetadataPath = jar.getPath("extras/unpick.json");
 
@@ -396,12 +405,25 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 			return;
 		}
 
-		Files.copy(unpickPath, extractTo, StandardCopyOption.REPLACE_EXISTING);
+		Files.copy(unpickPath, unpickDefinitions, StandardCopyOption.REPLACE_EXISTING);
 
 		unpickMetadata = parseUnpickMetadata(unpickMetadataPath);
 		hasUnpickDefinitions = true;
 	}
 
+	private void extractSignatureFixes(FileSystem jar) throws IOException {
+		Path recordSignaturesJsonPath = jar.getPath("extras/record_signatures.json");
+
+		if (!Files.exists(recordSignaturesJsonPath)) {
+			return;
+		}
+
+		try (Reader reader = Files.newBufferedReader(recordSignaturesJsonPath, StandardCharsets.UTF_8)) {
+			//noinspection unchecked
+			signatureFixes = LoomGradlePlugin.OBJECT_MAPPER.readValue(reader, Map.class);
+		}
+	}
+
 	private UnpickMetadata parseUnpickMetadata(Path input) throws IOException {
 		JsonObject jsonObject = LoomGradlePlugin.GSON.fromJson(Files.readString(input), JsonObject.class);
 
@@ -599,6 +621,11 @@ public class MappingsProviderImpl extends DependencyProvider implements Mappings
 		return hasUnpickDefinitions;
 	}
 
+	@Nullable
+	public Map<String, String> getSignatureFixes() {
+		return signatureFixes;
+	}
+
 	@Override
 	public File intermediaryTinyFile() {
 		try {
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayer.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayer.java
new file mode 100644
index 00000000..845eed60
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayer.java
@@ -0,0 +1,34 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.extras.signatures;
+
+import java.util.Map;
+
+import org.jetbrains.annotations.ApiStatus;
+
+@ApiStatus.Experimental
+public interface SignatureFixesLayer {
+	Map<String, String> getSignatureFixes();
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayerImpl.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayerImpl.java
new file mode 100644
index 00000000..5f906384
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesLayerImpl.java
@@ -0,0 +1,64 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.extras.signatures;
+
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.nio.file.Path;
+import java.util.Map;
+import java.util.Objects;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+import org.jetbrains.annotations.ApiStatus;
+
+import net.fabricmc.loom.LoomGradlePlugin;
+import net.fabricmc.loom.api.mappings.layered.MappingLayer;
+import net.fabricmc.mappingio.MappingVisitor;
+
+@ApiStatus.Experimental
+public record SignatureFixesLayerImpl(Path mappingsFile) implements MappingLayer, SignatureFixesLayer {
+	private static final String SIGNATURE_FIXES_PATH = "extras/record_signatures.json";
+
+	@Override
+	public void visit(MappingVisitor mappingVisitor) throws IOException {
+		// Nothing to do here
+	}
+
+	@Override
+	public Map<String, String> getSignatureFixes() {
+		try (var zipFile = new ZipFile(mappingsFile().toFile())) {
+			ZipEntry zipFileEntry = zipFile.getEntry(SIGNATURE_FIXES_PATH);
+			Objects.requireNonNull(zipFileEntry, "Could not find %s in file".formatted(SIGNATURE_FIXES_PATH));
+
+			try (var reader = new InputStreamReader(zipFile.getInputStream(zipFileEntry))) {
+				//noinspection unchecked
+				return LoomGradlePlugin.OBJECT_MAPPER.readValue(reader, Map.class);
+			}
+		} catch (IOException e) {
+			throw new RuntimeException("Failed to extract signature fixes", e);
+		}
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesSpec.java b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesSpec.java
new file mode 100644
index 00000000..1f4f1ae5
--- /dev/null
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/mappings/extras/signatures/SignatureFixesSpec.java
@@ -0,0 +1,39 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2021 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.configuration.providers.mappings.extras.signatures;
+
+import org.jetbrains.annotations.ApiStatus;
+
+import net.fabricmc.loom.api.mappings.layered.MappingContext;
+import net.fabricmc.loom.api.mappings.layered.spec.FileSpec;
+import net.fabricmc.loom.api.mappings.layered.spec.MappingsSpec;
+
+@ApiStatus.Experimental
+public record SignatureFixesSpec(FileSpec fileSpec) implements MappingsSpec<SignatureFixesLayerImpl> {
+	@Override
+	public SignatureFixesLayerImpl createLayer(MappingContext context) {
+		return new SignatureFixesLayerImpl(fileSpec.get(context));
+	}
+}
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java b/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
index 5d03b971..49ddccd1 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/minecraft/MinecraftMappedProvider.java
@@ -30,9 +30,13 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicReference;
 import java.util.function.Consumer;
 
 import com.google.common.base.Stopwatch;
@@ -41,10 +45,13 @@ import dev.architectury.tinyremapper.InputTag;
 import dev.architectury.tinyremapper.NonClassCopyMode;
 import dev.architectury.tinyremapper.OutputConsumerPath;
 import dev.architectury.tinyremapper.TinyRemapper;
+import dev.architectury.tinyremapper.api.TrClass;
 import org.apache.commons.lang3.mutable.Mutable;
-import org.apache.commons.lang3.tuple.Pair;
+import org.apache.commons.lang3.tuple.Triple;
 import org.gradle.api.Project;
 import org.jetbrains.annotations.Nullable;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.commons.Remapper;
 
 import net.fabricmc.loom.api.mappings.layered.MappingsNamespace;
 import net.fabricmc.loom.configuration.DependencyProvider;
@@ -230,8 +237,8 @@ public class MinecraftMappedProvider extends DependencyProvider {
 		Info vanilla = new Info(vanillaAssets, input, outputMapped, outputIntermediary, outputSrg);
 		Info forge = getExtension().isForgeAndNotOfficial() ? new Info(forgeAssets, inputForge, forgeOutputMapped, forgeOutputIntermediary, forgeOutputSrg) : null;
 
-		Pair<TinyRemapper, Mutable<MemoryMappingTree>> pair = TinyRemapperHelper.getTinyRemapper(getProject(), true);
-		TinyRemapper remapper = remapperArray[0] = pair.getKey();
+		Triple<TinyRemapper, Mutable<MemoryMappingTree>, List<TinyRemapper.ApplyVisitorProvider>> pair = TinyRemapperHelper.getTinyRemapper(getProject(), true, builder -> { });
+		TinyRemapper remapper = remapperArray[0] = pair.getLeft();
 
 		assetsOut(input, vanillaAssets);
 
@@ -239,7 +246,7 @@ public class MinecraftMappedProvider extends DependencyProvider {
 			assetsOut(inputForge, forgeAssets);
 		}
 
-		remap(remapper, pair.getValue(), vanilla, forge, MappingsNamespace.OFFICIAL.toString());
+		remap(remapper, pair.getMiddle(), pair.getRight(), vanilla, forge, MappingsNamespace.OFFICIAL.toString());
 	}
 
 	public static class Info {
@@ -258,7 +265,7 @@ public class MinecraftMappedProvider extends DependencyProvider {
 		}
 	}
 
-	public void remap(TinyRemapper remapper, Mutable<MemoryMappingTree> mappings, Info vanilla, @Nullable Info forge, String fromM) throws IOException {
+	public void remap(TinyRemapper remapper, Mutable<MemoryMappingTree> mappings, List<TinyRemapper.ApplyVisitorProvider> postApply, Info vanilla, @Nullable Info forge, String fromM) throws IOException {
 		Set<String> classNames = getExtension().isForge() ? InnerClassRemapper.readClassNames(vanilla.input) : null;
 
 		for (String toM : getExtension().isForge() ? Arrays.asList(MappingsNamespace.INTERMEDIARY.toString(), MappingsNamespace.SRG.toString(), MappingsNamespace.NAMED.toString()) : Arrays.asList(MappingsNamespace.INTERMEDIARY.toString(), MappingsNamespace.NAMED.toString())) {
@@ -267,6 +274,7 @@ public class MinecraftMappedProvider extends DependencyProvider {
 			InputTag vanillaTag = remapper.createInputTag();
 			InputTag forgeTag = remapper.createInputTag();
 			Stopwatch stopwatch = Stopwatch.createStarted();
+			final boolean fixSignatures = getExtension().getMappingsProvider().getSignatureFixes() != null;
 			getProject().getLogger().lifecycle(":remapping minecraft (TinyRemapper, " + fromM + " -> " + toM + ")");
 
 			remapper.readInputs(vanillaTag, vanilla.input);
@@ -277,6 +285,55 @@ public class MinecraftMappedProvider extends DependencyProvider {
 
 			remapper.replaceMappings(getMappings(classNames, fromM, toM, mappings));
 			if (!MappingsNamespace.INTERMEDIARY.toString().equals(toM)) mappings.setValue(null);
+			postApply.clear();
+
+			// Bit ugly but whatever, the whole issue is a bit ugly :)
+			AtomicReference<Map<String, String>> remappedSignatures = new AtomicReference<>();
+			if (fixSignatures) {
+				postApply.add(new TinyRemapper.ApplyVisitorProvider() {
+					@Override
+					public ClassVisitor insertApplyVisitor(TrClass cls, ClassVisitor next) {
+						return new ClassVisitor(Constants.ASM_VERSION, next) {
+							@Override
+							public void visit(int version, int access, String name, String signature, String superName, String[] interfaces) {
+								Map<String, String> signatureFixes = Objects.requireNonNull(remappedSignatures.get(), "Could not get remapped signatures");
+
+								if (signature == null) {
+									signature = signatureFixes.getOrDefault(name, null);
+
+									if (signature != null) {
+										getProject().getLogger().info("Replaced signature for {} with {}", name, signature);
+									}
+								}
+
+								super.visit(version, access, name, signature, superName, interfaces);
+							}
+						};
+					}
+				});
+
+				if (MappingsNamespace.INTERMEDIARY.toString().equals(toM)) {
+					// No need to remap, as these are already intermediary
+					remappedSignatures.set(getExtension().getMappingsProvider().getSignatureFixes());
+				} else {
+					// Remap the sig fixes from intermediary to the target namespace
+					final Map<String, String> remapped = new HashMap<>();
+					final TinyRemapper sigTinyRemapper = TinyRemapperHelper.getTinyRemapper(getProject(), fromM, toM);
+					final Remapper sigAsmRemapper = sigTinyRemapper.getRemapper();
+
+					// Remap the class names and the signatures using a new tiny remapper instance.
+					for (Map.Entry<String, String> entry : getExtension().getMappingsProvider().getSignatureFixes().entrySet()) {
+						remapped.put(
+								sigAsmRemapper.map(entry.getKey()),
+								sigAsmRemapper.mapSignature(entry.getValue(), false)
+						);
+					}
+
+					sigTinyRemapper.finish();
+					remappedSignatures.set(remapped);
+				}
+			}
+
 			OutputRemappingHandler.remap(remapper, vanilla.assets, output, null, vanillaTag);
 
 			if (forge != null) {
diff --git a/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java b/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java
index b9af8fb8..45ccb6c7 100644
--- a/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java
+++ b/src/main/java/net/fabricmc/loom/util/TinyRemapperHelper.java
@@ -27,7 +27,10 @@ package net.fabricmc.loom.util;
 import java.io.File;
 import java.io.IOException;
 import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
+import java.util.function.Consumer;
 import java.util.regex.Pattern;
 
 import com.google.common.collect.ImmutableMap;
@@ -37,6 +40,7 @@ import dev.architectury.tinyremapper.TinyRemapper;
 import org.apache.commons.lang3.mutable.Mutable;
 import org.apache.commons.lang3.mutable.MutableObject;
 import org.apache.commons.lang3.tuple.Pair;
+import org.apache.commons.lang3.tuple.Triple;
 import org.gradle.api.Project;
 
 import net.fabricmc.loom.LoomGradleExtension;
@@ -63,13 +67,13 @@ public final class TinyRemapperHelper {
 	}
 
 	public static TinyRemapper getTinyRemapper(Project project, String fromM, String toM) throws IOException {
-		return getTinyRemapper(project, fromM, toM, false);
+		return getTinyRemapper(project, fromM, toM, false, (builder) -> { });
 	}
 
-	public static TinyRemapper getTinyRemapper(Project project, String fromM, String toM, boolean fixRecords) throws IOException {
+	public static TinyRemapper getTinyRemapper(Project project, String fromM, String toM, boolean fixRecords, Consumer<TinyRemapper.Builder> builderConsumer) throws IOException {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
 
-		TinyRemapper remapper = _getTinyRemapper(project, fixRecords).getKey();
+		TinyRemapper remapper = _getTinyRemapper(project, fixRecords, builderConsumer).getLeft();
 		remapper.replaceMappings(ImmutableSet.of(
 				TinyRemapperHelper.create((fromM.equals("srg") || toM.equals("srg")) && extension.isForge() ? extension.getMappingsProvider().getMappingsWithSrg() : extension.getMappingsProvider().getMappings(), fromM, toM, true),
 				out -> TinyRemapperHelper.JSR_TO_JETBRAINS.forEach(out::acceptClass)
@@ -77,9 +81,10 @@ public final class TinyRemapperHelper {
 		return remapper;
 	}
 
-	public static Pair<TinyRemapper, Mutable<MemoryMappingTree>> _getTinyRemapper(Project project, boolean fixRecords) throws IOException {
+	public static Triple<TinyRemapper, Mutable<MemoryMappingTree>, List<TinyRemapper.ApplyVisitorProvider>> _getTinyRemapper(Project project, boolean fixRecords, Consumer<TinyRemapper.Builder> builderConsumer) throws IOException {
 		LoomGradleExtension extension = LoomGradleExtension.get(project);
 		Mutable<MemoryMappingTree> mappings = new MutableObject<>();
+		List<TinyRemapper.ApplyVisitorProvider> postApply = new ArrayList<>();
 
 		TinyRemapper.Builder builder = TinyRemapper.newRemapper()
 				.renameInvalidLocals(true)
@@ -97,22 +102,30 @@ public final class TinyRemapperHelper {
 			builder.fixPackageAccess(true);
 		}
 
-		TinyRemapper remapper = builder.invalidLvNamePattern(MC_LV_PATTERN)
-				.extraPreApplyVisitor((cls, next) -> {
-					if (fixRecords && !cls.isRecord() && "java/lang/Record".equals(cls.getSuperName()) && mappings.getValue() != null) {
-						return new RecordComponentFixVisitor(next, mappings.getValue(), mappings.getValue().getNamespaceId(MappingsNamespace.INTERMEDIARY.toString()));
-					}
+		builder.invalidLvNamePattern(MC_LV_PATTERN);
+		builder.extraPreApplyVisitor((cls, next) -> {
+			if (fixRecords && !cls.isRecord() && "java/lang/Record".equals(cls.getSuperName()) && mappings.getValue() != null) {
+				return new RecordComponentFixVisitor(next, mappings.getValue(), mappings.getValue().getNamespaceId(MappingsNamespace.INTERMEDIARY.toString()));
+			}
+
+			return next;
+		});
+		builder.extraPostApplyVisitor((trClass, classVisitor) -> {
+			for (TinyRemapper.ApplyVisitorProvider provider : postApply) {
+				classVisitor = provider.insertApplyVisitor(trClass, classVisitor);
+			}
+
+			return classVisitor;
+		});
 
-					return next;
-				})
-				.build();
-		return Pair.of(remapper, mappings);
+		builderConsumer.accept(builder);
+		return Triple.of(builder.build(), mappings, postApply);
 	}
 
-	public static Pair<TinyRemapper, Mutable<MemoryMappingTree>> getTinyRemapper(Project project, boolean fixRecords) throws IOException {
-		Pair<TinyRemapper, Mutable<MemoryMappingTree>> remapper = _getTinyRemapper(project, fixRecords);
-		remapper.getKey().readClassPath(getMinecraftDependencies(project));
-		remapper.getKey().prepareClasses();
+	public static Triple<TinyRemapper, Mutable<MemoryMappingTree>, List<TinyRemapper.ApplyVisitorProvider>> getTinyRemapper(Project project, boolean fixRecords, Consumer<TinyRemapper.Builder> builderConsumer) throws IOException {
+		Triple<TinyRemapper, Mutable<MemoryMappingTree>, List<TinyRemapper.ApplyVisitorProvider>> remapper = _getTinyRemapper(project, fixRecords, builderConsumer);
+		remapper.getLeft().readClassPath(getMinecraftDependencies(project));
+		remapper.getLeft().prepareClasses();
 		return remapper;
 	}