Fixup line numbers in forge source

1 files changed, 42 insertions, 0 deletions

diff --git a/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java b/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java
index 5b523153..6456f882 100644
--- a/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java
+++ b/src/main/java/net/fabricmc/loom/configuration/sources/ForgeSourcesRemapper.java
@@ -28,9 +28,12 @@ import java.io.File;
 import java.io.IOException;
 import java.io.PrintStream;
 import java.io.UncheckedIOException;
+import java.nio.file.FileVisitResult;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.SimpleFileVisitor;
 import java.nio.file.StandardOpenOption;
+import java.nio.file.attribute.BasicFileAttributes;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.List;
@@ -39,6 +42,7 @@ import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.BiConsumer;
 import java.util.stream.Collectors;
+import java.util.stream.IntStream;
 
 import org.apache.commons.io.output.NullOutputStream;
 import org.cadixdev.lorenz.MappingSet;
@@ -229,6 +233,7 @@ public class ForgeSourcesRemapper {
 		try (FileSystemUtil.Delegate outputFs = FileSystemUtil.getJarFileSystem(tmpOutput, true)) {
 			Path outputFsRoot = outputFs.get().getPath("/");
 			mercury.rewrite(tmpInput, outputFsRoot);
+			fixupLineNumbers(tmpInput, outputFsRoot);
 		} catch (Exception e) {
 			project.getLogger().warn("Could not remap " + tmpInput + " fully!", e);
 		}
@@ -256,4 +261,41 @@ public class ForgeSourcesRemapper {
 		taskCompleter.complete();
 		return sources;
 	}
+
+	/**
+	 * Mercury re-organizes imports during remapping, which can result in mismatching line information when debugging.
+	 * This method works around the issue by forcefully re-aligning the output files with the input files by inserting
+	 * empty lines or joining multiple lines into one.
+	 */
+	private static void fixupLineNumbers(Path srcRoot, Path outRoot) throws IOException {
+		Files.walkFileTree(srcRoot, new SimpleFileVisitor<>() {
+			@Override
+			public FileVisitResult visitFile(Path srcPath, BasicFileAttributes attrs) throws IOException {
+				Path outPath = outRoot.resolve(srcRoot.relativize(srcPath).toString());
+				List<String> src = Files.readAllLines(srcPath);
+				List<String> out = Files.readAllLines(outPath);
+				int lastSrc = IntStream.range(0, src.size()).filter(i -> src.get(i).startsWith("import")).max().orElse(0);
+				int lastOut = IntStream.range(0, out.size()).filter(i -> out.get(i).startsWith("import")).max().orElse(0);
+
+				if (lastSrc == lastOut) {
+					return FileVisitResult.CONTINUE;
+				}
+
+				while (lastOut < lastSrc) {
+					out.add(lastOut + 1, "");
+					lastOut++;
+				}
+
+				while (lastSrc < lastOut && lastOut > 0) {
+					out.set(lastOut - 1, out.get(lastOut - 1) + out.get(lastOut));
+					out.remove(lastOut);
+					lastOut--;
+				}
+
+				Files.write(outPath, out);
+
+				return FileVisitResult.CONTINUE;
+			}
+		});
+	}
 }