Add a new merge mappings command that works with partial parameter mappings.

build.gradle

@@ -75,6 +75,12 @@ dependencies {
     implementation 'de.siegmar:fastcsv:2.0.0'
     implementation 'org.ow2.asm:asm-commons:9.3'
     implementation project(':cli-utils')
+
+    testImplementation(libs.bundles.junit)
+}
+
+test {
+    useJUnitPlatform()
 }
 
 publishing {

src/main/java/net/neoforged/installertools/MergeMappings.java

@@ -18,42 +18,65 @@
  */
 package net.neoforged.installertools;
 
+import joptsimple.OptionException;
+import joptsimple.OptionParser;
+import joptsimple.OptionSet;
+import joptsimple.OptionSpec;
 import net.neoforged.srgutils.IMappingFile;
-import net.neoforged.srgutils.IRenamer;
-import net.neoforged.srgutils.IMappingFile.IClass;
-import net.neoforged.srgutils.IMappingFile.IField;
-import net.neoforged.srgutils.IMappingFile.IMethod;
-import net.neoforged.srgutils.IMappingFile.IPackage;
-import net.neoforged.srgutils.IMappingFile.IParameter;
 
-public class MergeMappings extends ChainMappings {
+import java.io.File;
+import java.io.IOException;
+
+public class MergeMappings extends Task {
     @Override
-    protected IRenamer makeRenamer(IMappingFile link, boolean classes, boolean fields, boolean methods, boolean params) {
-        return new IRenamer() {
-            public String rename(IPackage value) {
-                return link.remapPackage(value.getOriginal());
-            }
+    public void process(String[] args) throws IOException {
+        OptionParser parser = new OptionParser();
+        OptionSpec<File> base = parser.accepts("base").withRequiredArg().ofType(File.class).required();
+        OptionSpec<Void> reverseBase = parser.accepts("reverse-base");
+        OptionSpec<File> merge = parser.accepts("merge").withRequiredArg().ofType(File.class).required();
+        OptionSpec<Void> reverseMerge = parser.accepts("reverse-merge");
+        OptionSpec<File> output = parser.accepts("output").withRequiredArg().ofType(File.class).required();
+        OptionSpec<Void> reverseOutput = parser.accepts("reverse-output");
 
-            public String rename(IClass value) {
-                return classes ? link.remapClass(value.getOriginal()) : value.getMapped();
-            }
+        try {
+            OptionSet options = parser.parse(args);
 
-            public String rename(IField value) {
-                IClass cls = link.getClass(value.getParent().getOriginal());
-                return cls == null || !fields ? value.getMapped() : cls.remapField(value.getOriginal());
-            }
+            merge(
+                    options.valueOf(base),
+                    options.has(reverseBase),
+                    options.valueOf(merge),
+                    options.has(reverseMerge),
+                    options.valueOf(output),
+                    options.has(reverseOutput)
+            );
+        } catch (OptionException e) {
+            parser.printHelpOn(System.out);
+            error("Please provide correct parameters");
+        }
+    }
 
-            public String rename(IMethod value) {
-                IClass cls = link.getClass(value.getParent().getOriginal());
-                return cls == null || !methods ? value.getMapped() : cls.remapMethod(value.getOriginal(), value.getDescriptor());
-            }
+    private void merge(File baseFile, boolean reverseBase,
+                       File mergeFile, boolean reverseMerge,
+                       File outputFile, boolean reverseOutput) throws IOException {
+        log("Base Mappings: " + baseFile);
+        log("Reverse Base Mappings: " + reverseBase);
+        log("Merge Mappings: " + mergeFile);
+        log("Reverse Merge Mappings: " + reverseMerge);
+        log("Output: " + outputFile);
+        log("Reverse Output: " + reverseOutput);
 
-            public String rename(IParameter value) {
-                IMethod mtd = value.getParent();
-                IClass cls = link.getClass(mtd.getParent().getOriginal());
-                mtd = cls == null ? null : cls.getMethod(mtd.getOriginal(), mtd.getDescriptor());
-                return mtd == null || !params ? value.getMapped() : mtd.remapParameter(value.getIndex(), value.getMapped());
-            }
-        };
+        IMappingFile baseMappings = IMappingFile.load(baseFile);
+        if (reverseBase) {
+            baseMappings = baseMappings.reverse();
+        }
+        IMappingFile mergeMappings = IMappingFile.load(mergeFile);
+        if (reverseMerge) {
+            mergeMappings = mergeMappings.reverse();
+        }
+        IMappingFile outputMappings = baseMappings.merge(mergeMappings);
+        if (reverseOutput) {
+            outputMappings = outputMappings.reverse();
+        }
+        outputMappings.write(outputFile.toPath(), IMappingFile.Format.TSRG2, false);
     }
 }

src/test/java/net/neoforged/installertools/MergeMappingsTest.java

@@ -0,0 +1,35 @@
+package net.neoforged.installertools;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class MergeMappingsTest {
+    @TempDir
+    Path tempDir;
+
+    @Test
+    void testMergeMappings() throws Exception {
+        Path neoFormMappings = Paths.get(getClass().getResource("/neoform_mappings.tsrg").toURI());
+        Path officialMappings = Paths.get(getClass().getResource("/official.txt").toURI());
+        Path expectedMappings = Paths.get(getClass().getResource("/expected_merged_mappings.tsrg").toURI());
+        Path outputPath = tempDir.resolve("output.txt");
+
+        // This is what NeoForm calls
+        new MergeMappings().process(new String[]{
+                "--base",
+                officialMappings.toAbsolutePath().toString(),
+                "--reverse-base",
+                "--merge",
+                neoFormMappings.toAbsolutePath().toString(),
+                "--output",
+                outputPath.toString()
+        });
+
+        assertThat(outputPath).hasSameTextualContentAs(expectedMappings);
+    }
+}

src/test/resources/expected_merged_mappings.tsrg

@@ -0,0 +1,10 @@
+tsrg2 left right
+a pkg/CoolName
+	a F NOT_MENTIONED_FIELD
+	a (FF)V coolMethod
+		0 o p_254025_
+		1 o p_254401_
+	b ()D noParams
+b pkg/NotMentionedClass
+	a F NOT_MENTIONED_FIELD
+	b ()V notMentionedMethod

src/test/resources/neoform_mappings.tsrg

@@ -0,0 +1,5 @@
+tsrg2 obf srg
+a -
+	a (FF)V -
+		0 o p_254025_
+		1 o p_254401_

src/test/resources/official.txt

@@ -0,0 +1,10 @@
+# This emulates the format used by mojang mappings
+pkg.CoolName -> a:
+# {"fileName":"CoolName.java","id":"sourceFile"}
+    float NOT_MENTIONED_FIELD -> a
+    9:10:void coolMethod(float,float) -> a
+    13:13:double noParams() -> b
+pkg.NotMentionedClass -> b:
+# {"fileName":"NotMentionedClass.java","id":"sourceFile"}
+    float NOT_MENTIONED_FIELD -> a
+    6:8:void notMentionedMethod() -> b