Fix and test line number remapper (#1097)

src/main/java/net/fabricmc/loom/decompilers/LineNumberRemapper.java

@@ -60,12 +60,11 @@ public void processEntryAsync(Path file, Path dst) throws IOException {
 					}
 				}
 
-				String fileName = file.getFileName().toString();
+				String fileName = file.toAbsolutePath().toString();
 
 				if (fileName.endsWith(".class")) {
-					String idx = fileName.substring(0, fileName.length() - 6);
-
-					LOGGER.debug("Remapping line numbers for class: " + idx);
+					// Strip the leading slash and the .class extension
+					String idx = fileName.substring(1, fileName.length() - 6);
 
 					int dollarPos = idx.indexOf('$'); //This makes the assumption that only Java classes are to be remapped.
 
@@ -74,6 +73,8 @@ public void processEntryAsync(Path file, Path dst) throws IOException {
 					}
 
 					if (lineNumbers.lineMap().containsKey(idx)) {
+						LOGGER.debug("Remapping line numbers for class: {}", idx);
+
 						try (InputStream is = Files.newInputStream(file)) {
 							ClassReader reader = new ClassReader(is);
 							ClassWriter writer = new ClassWriter(0);
@@ -82,6 +83,8 @@ public void processEntryAsync(Path file, Path dst) throws IOException {
 							Files.write(dst, writer.toByteArray());
 							return;
 						}
+					} else {
+						LOGGER.debug("No linemap found for: {}", idx);
 					}
 				}
 

src/test/groovy/net/fabricmc/loom/test/integration/DebugLineNumbersTest.groovy

@@ -122,6 +122,8 @@ class DebugLineNumbersTest extends Specification implements GradleProjectTestTra
 				def result = it.get()
 				println("Breakpoint triggered: ${result.location()}")
 			}
+
+			println("All breakpoints triggered")
 		} finally {
 			// Close the debugger and target process
 			debugger.close()

src/test/groovy/net/fabricmc/loom/test/unit/LineNumberRemapperTests.groovy

@@ -0,0 +1,108 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2024 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.test.unit
+
+import java.nio.file.Files
+
+import org.objectweb.asm.ClassReader
+import org.objectweb.asm.ClassVisitor
+import org.objectweb.asm.Label
+import org.objectweb.asm.MethodVisitor
+import spock.lang.Specification
+
+import net.fabricmc.loom.decompilers.ClassLineNumbers
+import net.fabricmc.loom.decompilers.LineNumberRemapper
+import net.fabricmc.loom.test.util.ZipTestUtils
+import net.fabricmc.loom.util.Constants
+import net.fabricmc.loom.util.ZipUtils
+
+class LineNumberRemapperTests extends Specification {
+	def "remapLinenumbers"() {
+		given:
+		def className = LineNumberSource.class.name.replace('.', '/')
+		def input = ZipTestUtils.createZipFromBytes([(className + ".class"): getClassBytes(LineNumberSource.class)])
+
+		// + 10 to each line number
+		def entry = new ClassLineNumbers.Entry(className, 30, 40, [
+			27: 37,
+			29: 39,
+			30: 40
+		])
+		def lineNumbers = new ClassLineNumbers([(className): entry])
+
+		def outputJar = Files.createTempDirectory("loom").resolve("output.jar")
+
+		when:
+		def remapper = new LineNumberRemapper(lineNumbers)
+		remapper.process(input, outputJar)
+
+		def unpacked = ZipUtils.unpack(outputJar, className + ".class")
+
+		then:
+		readLineNumbers(getClassBytes(LineNumberSource.class)) == [27, 29, 30]
+		readLineNumbers(unpacked) == [37, 39, 40]
+	}
+
+	static byte[] getClassBytes(Class<?> clazz) {
+		return clazz.classLoader.getResourceAsStream(clazz.name.replace('.', '/') + ".class").withCloseable {
+			it.bytes
+		}
+	}
+
+	static List<Integer> readLineNumbers(byte[] clazzBytes) {
+		def reader = new ClassReader(clazzBytes)
+		def visitor = new LineNumberCollectorClassVisitor()
+		reader.accept(visitor, 0)
+		return visitor.lineNumbers
+	}
+
+	private static class LineNumberCollectorClassVisitor extends ClassVisitor {
+		final List<Integer> lineNumbers = []
+
+		protected LineNumberCollectorClassVisitor() {
+			super(Constants.ASM_VERSION)
+		}
+
+		@Override
+		MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+			return new LineNumberCollectorMethodVisitor(super.visitMethod(access, name, descriptor, signature, exceptions), lineNumbers)
+		}
+	}
+
+	private static class LineNumberCollectorMethodVisitor extends MethodVisitor {
+		final List<Integer> lineNumbers
+
+		protected LineNumberCollectorMethodVisitor(MethodVisitor methodVisitor, List<Integer> lineNumbers) {
+			super(Constants.ASM_VERSION, methodVisitor)
+			this.lineNumbers = lineNumbers
+		}
+
+		@Override
+		void visitLineNumber(int line, Label start) {
+			super.visitLineNumber(line, start)
+			lineNumbers.add(line)
+		}
+	}
+}

src/test/groovy/net/fabricmc/loom/test/util/ZipTestUtils.groovy

@@ -34,6 +34,15 @@ import net.fabricmc.loom.util.FileSystemUtil
 
 class ZipTestUtils {
 	static Path createZip(Map<String, String> entries) {
+		return createZipFromBytes(entries.collectEntries { k, v ->
+			[
+				k,
+				v.getBytes(StandardCharsets.UTF_8)
+			]
+		})
+	}
+
+	static Path createZipFromBytes(Map<String, byte[]> entries) {
 		def file = Files.createTempFile("loom-test", ".zip")
 		Files.delete(file)
 
@@ -42,7 +51,7 @@ class ZipTestUtils {
 				def fsPath = zip.getPath(path)
 				def fsPathParent = fsPath.getParent()
 				if (fsPathParent != null) Files.createDirectories(fsPathParent)
-				Files.writeString(fsPath, value, StandardCharsets.UTF_8)
+				Files.write(fsPath, value)
 			}
 		}
 

src/test/java/net/fabricmc/loom/test/unit/LineNumberSource.java

@@ -0,0 +1,31 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2024 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.test.unit;
+
+public class LineNumberSource {
+	public static void main(String[] args) {
+		System.out.println("Hello World!");
+	}
+}