Improve validation of cached ClassEntry's

src/main/java/net/fabricmc/loom/decompilers/cache/ClassEntry.java

@@ -45,6 +45,34 @@
 public record ClassEntry(String name, List<String> innerClasses, List<String> superClasses) {
 	private static final Logger LOGGER = LoggerFactory.getLogger(ClassEntry.class);
 
+	public ClassEntry {
+		if (!name.endsWith(".class")) {
+			throw new IllegalArgumentException("Class name must end with '.class': " + name);
+		}
+
+		if (!name.contains("/")) {
+			throw new IllegalArgumentException("Class name must be in a package: " + name);
+		}
+
+		String pkgPath = name.substring(0, name.lastIndexOf('/') + 1);
+
+		for (String innerClass : innerClasses) {
+			if (!innerClass.endsWith(".class")) {
+				throw new IllegalArgumentException("Inner class name must end with '.class': " + name);
+			}
+
+			if (!innerClass.startsWith(pkgPath)) {
+				throw new IllegalArgumentException("Inner class (" + innerClass + ") is not in the same package as parent: " + name);
+			}
+		}
+
+		for (String superClass : superClasses) {
+			if (!superClass.endsWith(".class")) {
+				throw new IllegalArgumentException("Super class name must end with '.class': " + superClass);
+			}
+		}
+	}
+
 	/**
 	 * Copy the class and its inner classes to the target root.
 	 * @param sourceRoot The root of the source jar
@@ -55,13 +83,18 @@ public record ClassEntry(String name, List<String> innerClasses, List<String> su
 	public void copyTo(Path sourceRoot, Path targetRoot) throws IOException {
 		Path targetPath = targetRoot.resolve(name);
 		Files.createDirectories(targetPath.getParent());
-		Files.copy(sourceRoot.resolve(name), targetPath);
+		copy(sourceRoot.resolve(name), targetPath);
 
 		for (String innerClass : innerClasses) {
-			Files.copy(sourceRoot.resolve(innerClass), targetRoot.resolve(innerClass));
+			copy(sourceRoot.resolve(innerClass), targetRoot.resolve(innerClass));
 		}
 	}
 
+	private void copy(Path source, Path target) throws IOException {
+		LOGGER.debug("Copying class entry `{}` from `{}` to `{}`", name, source, target);
+		Files.copy(source, target);
+	}
+
 	/**
 	 * Hash the class and its inner classes using sha256.
 	 * @param root The root of the jar
@@ -95,7 +128,7 @@ public String hashSuperHierarchy(Map<String, String> hashes) throws IOException
 		joiner.add(selfHash);
 
 		for (String superClass : superClasses) {
-			final String superHash = hashes.get(superClass + ".class");
+			final String superHash = hashes.get(superClass);
 
 			if (superHash != null) {
 				joiner.add(superHash);

src/main/java/net/fabricmc/loom/decompilers/cache/JarWalker.java

@@ -195,10 +195,13 @@ private static List<String> getSuperClasses(String classFile, FileSystemUtil.Del
 			String superName = reader.getSuperName();
 
 			if (superName != null) {
-				parentClasses.add(superName);
+				parentClasses.add(superName + ".class");
+			}
+
+			for (String iface : reader.getInterfaces()) {
+				parentClasses.add(iface + ".class");
 			}
 
-			Collections.addAll(parentClasses, reader.getInterfaces());
 			return Collections.unmodifiableList(parentClasses);
 		} catch (IOException e) {
 			throw new UncheckedIOException("Failed to read class file: " + classFile, e);

src/test/groovy/net/fabricmc/loom/test/unit/cache/ClassEntryTest.groovy

@@ -0,0 +1,60 @@
+/*
+ * 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.cache
+
+import spock.lang.Specification
+
+import net.fabricmc.loom.decompilers.cache.ClassEntry
+
+class ClassEntryTest extends Specification {
+	def "valid class entry"() {
+		when:
+		def classEntry = new ClassEntry(name, innerClasses, superClasses)
+		then:
+		// Just make sure the constructor doesn't throw an exception
+		classEntry != null
+		where:
+		name | innerClasses | superClasses
+		"net/fabricmc/Test.class" | [] | []
+		"net/fabricmc/Test.class" | [
+			"net/fabricmc/Test\$Inner.class"
+		] | ["java/lang/List.class"]
+	}
+
+	def "invalid class entry"() {
+		when:
+		new ClassEntry(name, innerClasses, superClasses)
+		then:
+		thrown IllegalArgumentException
+		where:
+		name | innerClasses | superClasses
+		"net/fabricmc/Test" | [] | []
+		"net/fabricmc/Test.class" | ["net/fabricmc/Test\$Inner"] | ["java/lang/List.class"]
+		"net/fabricmc/Test.class" | [
+			"net/fabricmc/Test\$Inner.class"
+		] | ["java/lang/List"]
+		"net/fabricmc/Test.class" | ["net/Test\$Inner.class"] | ["java/lang/List.class"]
+	}
+}

src/test/resources/projects/decompile/build.gradle

@@ -3,9 +3,9 @@ plugins {
 }
 
 dependencies {
-	minecraft "com.mojang:minecraft:21w38a"
-	mappings "net.fabricmc:yarn:21w38a+build.11:v2"
-	modImplementation "net.fabricmc:fabric-loader:0.11.7"
+	minecraft "com.mojang:minecraft:1.21.1"
+	mappings "net.fabricmc:yarn:1.21.1+build.3:v2"
+	modImplementation "net.fabricmc:fabric-loader:0.16.6"
 }
 
 loom {