Optimize the mappings file by removing superflous entries

build.gradle

@@ -781,13 +781,21 @@ subprojects {
         }
     }
 
+    def optimizeMappings = tasks.register('optimizeMappings', OptimizeJoinedSrg) {
+        input = file('joined.tsrg')
+        output = layout.buildDirectory.file('joined_stripped.tsrg')
+    }
+
     task makeZip(type: Zip, dependsOn: [generateConfiguration]) {
         archiveBaseName = rootProject.name
         archiveVersion = project.version
         destinationDirectory = file(PATH_BUILD + '/distributions')
 
         from generateConfiguration
-        from(file('joined.tsrg')){ into 'config/' }
+        from(optimizeMappings.flatMap(OptimizeJoinedSrg::getOutput)){
+            into 'config/'
+            rename { "joined.tsrg" }
+        }
 
         def patches = file('patches')
         if (patches.exists()) {

buildSrc/src/main/groovy/net/minecraftforge/mcpconfig/tasks/OptimizeJoinedSrg.groovy

@@ -0,0 +1,50 @@
+package net.minecraftforge.mcpconfig.tasks
+
+import net.neoforged.srgutils.IMappingBuilder
+import net.neoforged.srgutils.IMappingFile
+import org.gradle.api.DefaultTask
+import org.gradle.api.file.RegularFileProperty
+import org.gradle.api.tasks.InputFile
+import org.gradle.api.tasks.OutputFile
+import org.gradle.api.tasks.TaskAction
+
+/**
+ * Removes superflous entries from the mappings file.
+ * We only need method parameter mappings, so we can strip:
+ * - field mappings
+ * - methods without parameters
+ * - the SRG ID (for publication at least)
+ */
+abstract class OptimizeJoinedSrg extends DefaultTask {
+
+    @InputFile
+    abstract RegularFileProperty getInput()
+
+    @OutputFile
+    abstract RegularFileProperty getOutput()
+
+    @TaskAction
+    void optimize() {
+        var input = getInput().get().asFile
+        var output = getOutput().get().asFile
+
+        def srgInput = IMappingFile.load(input)
+
+        // Drop anything but parameter names
+        def srgOutput = IMappingBuilder.create("obf", "srg")
+        for (var srcClass : srgInput.classes) {
+            var dstClass = srgOutput.addClass(srcClass.original, "-")
+            for (var srcMethod : srcClass.methods) {
+                if (srcMethod.parameters.isEmpty()) {
+                    continue // Skip methods with no parameters
+                }
+                var dstMethod = dstClass.method(srcMethod.descriptor, srcMethod.original, "-")
+                for (var srcParam in srcMethod.parameters) {
+                    dstMethod.parameter(srcParam.index, "-", srcParam.mapped)
+                }
+            }
+        }
+        srgOutput.build().write(output.toPath(), IMappingFile.Format.TSRG2)
+    }
+
+}

versions/release/1.21.4/config.json

@@ -20,16 +20,16 @@
         "args": ["--input", "{input}", "--output", "{output}", "--map", "{mappings}", "--cfg", "{libraries}", "--ann-fix", "--ids-fix", "--src-fix", "--record-fix", "--unfinal-params"]
     },
     "bundler_extract_jar": {
-        "version": "net.neoforged.installertools:installertools:2.1.2:fatjar",
+        "version": "net.neoforged.installertools:installertools:3.0.2:fatjar",
         "args": ["--task", "bundler_extract", "--input", "{input}", "--output", "{output}", "--jar-only"]
     },
     "bundler_extract_libs": {
-        "version": "net.neoforged.installertools:installertools:2.1.2:fatjar",
+        "version": "net.neoforged.installertools:installertools:3.0.2:fatjar",
         "args": ["--task", "bundler_extract", "--input", "{input}", "--output", "{output}", "--libraries"]
     },
     "mergemap": {
-        "version": "net.neoforged.installertools:installertools:2.1.2:fatjar",
-        "args": ["--task", "MERGE_MAPPING", "--left", "{mappings}", "--right", "{official}", "--right-names", "right,left", "--classes", "--fields", "--methods", "--output", "{output}"]
+        "version": "net.neoforged.installertools:installertools:3.0.2:fatjar",
+        "args": ["--task", "MERGE_MAPPING", "--base", "{official}", "--reverse-base", "--merge", "{mappings}", "--output", "{output}"]
     },
     "libraries": {
         "client": ["com.google.code.findbugs:jsr305:3.0.2", "ca.weblite:java-objc-bridge:1.1", "org.jetbrains:annotations:26.0.1"],