Add class file down sampling

dependencies.gradle

@@ -28,6 +28,8 @@ project.ext {
     directories = 'dev.dirs:directories:26'
     docking = 'com.github.Col-E:tiwulfx-dock:1.2.3'
 
+    downgrader = 'com.github.RaphiMC.JavaDowngrader:core:13e29798a8'
+
     extra_collections = 'software.coley:extra-collections:1.2.3'
     extra_observables = 'software.coley:extra-observables:1.2.2'
 

recaf-api/build.gradle

@@ -31,6 +31,10 @@ dependencies {
         exclude group: 'com.android.tools'
     }
     api directories
+    api(downgrader) {
+        exclude group: 'org.ow2.asm'
+        exclude group: 'org.slf4j'
+    }
     api extra_collections
     api extra_observables
     api gson // required by R8 (from dex-translator)

recaf-api/src/main/java/software/coley/recaf/services/compile/CompileMap.java

@@ -1,5 +1,13 @@
 package software.coley.recaf.services.compile;
 
+import net.raphimc.javadowngrader.JavaDowngrader;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.tree.ClassNode;
+import org.slf4j.Logger;
+import software.coley.recaf.analytics.logging.Logging;
+
+import java.util.HashSet;
 import java.util.Map;
 import java.util.TreeMap;
 
@@ -9,6 +17,8 @@
  * @author Matt Coley
  */
 public class CompileMap extends TreeMap<String, byte[]> {
+	private static final Logger logger = Logging.get(CompileMap.class);
+
 	/**
 	 * @param map
 	 * 		Map to copy.
@@ -39,4 +49,28 @@ public boolean hasInnerClasses() {
 		}
 		return false;
 	}
+
+	/**
+	 * Down sample all classes in the map to the target version.
+	 *
+	 * @param version
+	 * 		Target version to downsample to.
+	 */
+	public void downsample(int version) {
+		for (Map.Entry<String, byte[]> entry : new HashSet<>(entrySet())) {
+			String key = entry.getKey();
+			try {
+				ClassNode node = new ClassNode();
+				new ClassReader(entry.getValue()).accept(node, 0);
+				if (node.version > version) {
+					JavaDowngrader.downgrade(node, version);
+					ClassWriter writer = new ClassWriter(0);
+					node.accept(writer);
+					put(key, writer.toByteArray());
+				}
+			} catch (Throwable t) {
+				logger.error("Failed down sampling '{}' to version {}", key, version, t);
+			}
+		}
+	}
 }

recaf-api/src/main/java/software/coley/recaf/services/compile/JavacArguments.java

@@ -19,6 +19,7 @@ public class JavacArguments {
 	// Options
 	private final String classPath;
 	private final int versionTarget;
+	private final int downsampleTarget;
 	private final boolean debugVariables;
 	private final boolean debugLineNumbers;
 	private final boolean debugSourceName;
@@ -31,7 +32,9 @@ public class JavacArguments {
 	 * @param classPath
 	 * 		Classpath to use with compiler.
 	 * @param versionTarget
-	 * 		Java bytecode version to target.
+	 * 		Java version to target.
+	 * @param downsampleTarget
+	 * 		Java version to target via down sampling. Negative to disable downs sampling.
 	 * @param debugVariables
 	 * 		Debug flag to include variable info.
 	 * @param debugLineNumbers
@@ -40,12 +43,13 @@ public class JavacArguments {
 	 * 		Debug flag to include source file name.
 	 */
 	public JavacArguments(@Nonnull String className, @Nonnull String classSource,
-						  @Nullable String classPath, int versionTarget,
+						  @Nullable String classPath, int versionTarget, int downsampleTarget,
 						  boolean debugVariables, boolean debugLineNumbers, boolean debugSourceName) {
 		this.className = className;
 		this.classSource = classSource;
 		this.classPath = classPath;
 		this.versionTarget = versionTarget;
+		this.downsampleTarget = downsampleTarget;
 		this.debugVariables = debugVariables;
 		this.debugLineNumbers = debugLineNumbers;
 		this.debugSourceName = debugSourceName;
@@ -100,12 +104,19 @@ public String getClassPath() {
 	}
 
 	/**
-	 * @return Java bytecode version to target.
+	 * @return Java version to target.
 	 */
 	public int getVersionTarget() {
 		return versionTarget;
 	}
 
+	/**
+	 * @return Java version to target via down sampling. Negative to disable downs sampling.
+	 */
+	public int getDownsampleTarget() {
+		return Math.min(downsampleTarget, JavacCompiler.MIN_DOWNSAMPLE_VER);
+	}
+
 	/**
 	 * @return Debug flag to include variable info.
 	 */

recaf-api/src/main/java/software/coley/recaf/services/compile/JavacArgumentsBuilder.java

@@ -14,6 +14,7 @@ public final class JavacArgumentsBuilder {
 	private String classSource;
 	private String classPath = System.getProperty("java.class.path");
 	private int versionTarget = JavaVersion.get();
+	private int downsampleTarget = -1;
 	private boolean debugVariables = true;
 	private boolean debugLineNumbers = true;
 	private boolean debugSourceName = true;
@@ -54,9 +55,22 @@ public JavacArgumentsBuilder withClassPath(@Nullable String classPath) {
 		return this;
 	}
 
+	/**
+	 * @param downsampleTarget
+	 * 		Java version to target via down sampling. Negative to disable downs sampling.
+	 * 		See: {@link JavacCompiler#MIN_DOWNSAMPLE_VER} for lowest supported target.
+	 *
+	 * @return Builder.
+	 */
+	@Nonnull
+	public JavacArgumentsBuilder withDownsampleTarget(int downsampleTarget) {
+		this.downsampleTarget = downsampleTarget;
+		return this;
+	}
+
 	/**
 	 * @param versionTarget
-	 * 		Java bytecode version to target.
+	 * 		Java version to target.
 	 *
 	 * @return Builder.
 	 */
@@ -113,7 +127,7 @@ public JavacArguments build() {
 			throw new IllegalArgumentException("Class source must not be null");
 
 		return new JavacArguments(className, classSource,
-				classPath, versionTarget,
+				classPath, versionTarget, downsampleTarget,
 				debugVariables, debugLineNumbers, debugSourceName);
 	}
 }

recaf-api/src/main/java/software/coley/recaf/services/compile/JavacCompiler.java

@@ -30,6 +30,7 @@
 @ApplicationScoped
 public class JavacCompiler implements Service {
 	public static final String SERVICE_ID = "java-compiler";
+	public static final int MIN_DOWNSAMPLE_VER = 8;
 	private static final DebuggingLogger logger = Logging.get(JavacCompiler.class);
 	private static final JavaCompiler compiler = ToolProvider.getSystemJavaCompiler();
 	private final JavacCompilerConfig config;
@@ -125,7 +126,13 @@ public CompilerResult compile(@Nonnull JavacArguments arguments,
 			} else {
 				logger.debugging(l -> l.error("Compilation of '{}' failed", className));
 			}
-			return new CompilerResult(unitMap.getCompilations(), diagnostics);
+			CompileMap compilations = unitMap.getCompilations();
+			int downsampleTarget = arguments.getDownsampleTarget();
+			if (downsampleTarget >= MIN_DOWNSAMPLE_VER)
+				compilations.downsample(downsampleTarget);
+			else if (downsampleTarget >= 0)
+				logger.warn("Cannot downsample beyond Java {}", JavacCompiler.MIN_DOWNSAMPLE_VER);
+			return new CompilerResult(compilations, diagnostics);
 		} catch (RuntimeException ex) {
 			logger.debugging(l -> l.error("Compilation of '{}' crashed: {}", className, ex));
 			return new CompilerResult(ex);

recaf-api/src/main/java/software/coley/recaf/services/compile/JavacCompilerConfig.java

@@ -25,13 +25,15 @@ public class JavacCompilerConfig extends BasicConfigContainer implements Service
 	private final ObservableBoolean generatePhantoms = new ObservableBoolean(true);
 	private final ObservableBoolean defaultEmitDebug = new ObservableBoolean(true);
 	private final ObservableInteger defaultTargetVersion = new ObservableInteger(-1);
+	private final ObservableInteger defaultDownsampleTargetVersion = new ObservableInteger(-1);
 
 	@Inject
 	public JavacCompilerConfig() {
 		super(ConfigGroups.SERVICE_COMPILE, JavacCompiler.SERVICE_ID + CONFIG_SUFFIX);
 		addValue(new BasicConfigValue<>("generate-phantoms", Boolean.class, generatePhantoms));
 		addValue(new BasicConfigValue<>("default-emit-debug", Boolean.class, defaultEmitDebug));
-		addValue(new BasicConfigValue<>("default-target-version", Integer.class, defaultTargetVersion));
+		addValue(new BasicConfigValue<>("default-compile-target-version", Integer.class, defaultTargetVersion));
+		addValue(new BasicConfigValue<>("default-downsample-target-version", Integer.class, defaultDownsampleTargetVersion));
 	}
 
 	/**
@@ -69,4 +71,16 @@ public ObservableBoolean getDefaultEmitDebug() {
 	public ObservableInteger getDefaultTargetVersion() {
 		return defaultTargetVersion;
 	}
+
+	/**
+	 * Not enforced internally by {@link JavacCompiler}.
+	 * Callers should check this value and ensure to call {@link JavacArgumentsBuilder#withDownsampleTarget(int)}.
+	 *
+	 * @return Negative to disable down sampling, otherwise target version to downsample compiled code to
+	 * <i>(In class file version format)</i>
+	 */
+	@Nonnull
+	public ObservableInteger getDefaultDownsampleTargetVersion() {
+		return defaultDownsampleTargetVersion;
+	}
 }

recaf-ui/src/main/java/software/coley/recaf/ui/pane/editing/jvm/JvmDecompilerPane.java

@@ -72,6 +72,7 @@ public class JvmDecompilerPane extends AbstractDecompilePane {
 	private static final Logger logger = Logging.get(JvmDecompilerPane.class);
 	private static final ExecutorService compilePool = ThreadPoolFactory.newSingleThreadExecutor("recompile");
 	private final ObservableInteger javacTarget;
+	private final ObservableInteger javacDownsampleTarget;
 	private final ObservableBoolean javacDebug;
 	private final ModalPaneComponent overlayModal = new ModalPaneComponent();
 	private final PhantomGenerator phantomGenerator;
@@ -93,11 +94,12 @@ public JvmDecompilerPane(@Nonnull DecompilerPaneConfig config,
 		this.phantomGenerator = phantomGenerator;
 		this.javacDebug = new ObservableBoolean(javacConfig.getDefaultEmitDebug().getValue());
 		this.javacTarget = new ObservableInteger(javacConfig.getDefaultTargetVersion().getValue());
+		this.javacDownsampleTarget = new ObservableInteger(javacConfig.getDefaultDownsampleTargetVersion().getValue());
 		this.javacConfig = javacConfig;
 		this.javac = javac;
 
 		// Install tools container with configurator
-		new JvmDecompilerPaneConfigurator(toolsContainer, config, decompiler, javacTarget, javacDebug, decompilerManager);
+		new JvmDecompilerPaneConfigurator(toolsContainer, config, decompiler, javacTarget, javacDownsampleTarget, javacDebug, decompilerManager);
 		toolsContainer.install(editor);
 
 		// Setup keybindings
@@ -171,6 +173,7 @@ private void save() {
 			boolean debug = javacDebug.getValue();
 			JavacArgumentsBuilder builder = new JavacArgumentsBuilder()
 					.withVersionTarget(useConfiguredVersion(info))
+					.withDownsampleTarget(javacDownsampleTarget.getValue())
 					.withDebugVariables(debug)
 					.withDebugSourceName(debug)
 					.withDebugLineNumbers(debug)

recaf-ui/src/main/java/software/coley/recaf/ui/pane/editing/jvm/JvmDecompilerPaneConfigurator.java

@@ -8,6 +8,7 @@
 import software.coley.observables.ObservableBoolean;
 import software.coley.observables.ObservableInteger;
 import software.coley.observables.ObservableObject;
+import software.coley.recaf.services.compile.JavacCompiler;
 import software.coley.recaf.services.decompile.DecompilerManager;
 import software.coley.recaf.services.decompile.JvmDecompiler;
 import software.coley.recaf.ui.control.BoundLabel;
@@ -26,6 +27,7 @@
  */
 public class JvmDecompilerPaneConfigurator extends AbstractDecompilerPaneConfigurator {
 	private final ObservableInteger javacTarget;
+	private final ObservableInteger javacDownsampleTarget;
 	private final ObservableBoolean javacDebug;
 
 	/**
@@ -37,6 +39,8 @@ public class JvmDecompilerPaneConfigurator extends AbstractDecompilerPaneConfigu
 	 * 		Local decompiler implementation.
 	 * @param javacTarget
 	 * 		Local target version for {@code javac}.
+	 * @param javacDownsampleTarget
+	 * 		Local target version to downsample to for {@code javac}.
 	 * @param javacDebug
 	 * 		Local debug flag for {@code javac}.
 	 * @param decompilerManager
@@ -46,10 +50,12 @@ public JvmDecompilerPaneConfigurator(@Nonnull ToolsContainerComponent toolsConta
 										 @Nonnull DecompilerPaneConfig config,
 										 @Nonnull ObservableObject<JvmDecompiler> decompiler,
 										 @Nonnull ObservableInteger javacTarget,
+										 @Nonnull ObservableInteger javacDownsampleTarget,
 										 @Nonnull ObservableBoolean javacDebug,
 										 @Nonnull DecompilerManager decompilerManager) {
 		super(toolsContainer, config, decompiler, decompilerManager);
 		this.javacTarget = javacTarget;
+		this.javacDownsampleTarget = javacDownsampleTarget;
 		this.javacDebug = javacDebug;
 	}
 
@@ -62,12 +68,20 @@ protected GridPane createGrid() {
 		Label compileTitle = new BoundLabel(Lang.getBinding("service.compile"));
 		compileTitle.getStyleClass().addAll(Styles.TEXT_UNDERLINED, Styles.TITLE_4);
 		Label labelTargetVersion = new BoundLabel(Lang.getBinding("java.targetversion"));
+		Label labelTargetDownsampleVersion = new BoundLabel(Lang.getBinding("java.targetdownsampleversion"));
 		Label labelDebug = new BoundLabel(Lang.getBinding("java.targetdebug"));
-		content.add(compileTitle, 0, 3, 2, 1);
-		content.add(labelTargetVersion, 0, 4);
-		content.add(fix(new JavacVersionComboBox()), 1, 4);
-		content.add(labelDebug, 0, 5);
-		content.add(fix(new ObservableCheckBox(javacDebug, Lang.getBinding("misc.enabled"))), 1, 5);
+
+		int row = content.getRowCount() + 1;
+		content.add(compileTitle, 0, row++, 2, 1);
+
+		content.add(labelTargetVersion, 0, row);
+		content.add(fix(new JavacVersionComboBox()), 1, row++);
+
+		content.add(labelTargetDownsampleVersion, 0, row);
+		content.add(fix(new JavacDownsampleVersionComboBox()), 1, row++);
+
+		content.add(labelDebug, 0, row);
+		content.add(fix(new ObservableCheckBox(javacDebug, Lang.getBinding("misc.enabled"))), 1, row++);
 
 		return content;
 	}
@@ -92,4 +106,25 @@ private JavacVersionComboBox() {
 			valueProperty().addListener((ob, old, cur) -> javacTarget.setValue(cur));
 		}
 	}
+
+	private class JavacDownsampleVersionComboBox extends ComboBox<Integer> {
+		private JavacDownsampleVersionComboBox() {
+			int max = JavaVersion.get();
+			for (int i = JavacCompiler.MIN_DOWNSAMPLE_VER; i <= max; i++)
+				getItems().add(i);
+
+			// Edge case for 'disabled'
+			getItems().add(-1);
+			setValue(-1);
+			setConverter(ToStringConverter.from(version -> {
+				int v = version;
+				if (v < 0)
+					return Lang.get("java.targetdownsampleversion.disabled");
+				return String.valueOf(v);
+			}));
+
+			// Update property.
+			valueProperty().addListener((ob, old, cur) -> javacDownsampleTarget.setValue(cur));
+		}
+	}
 }

recaf-ui/src/main/resources/translations/en_US.lang

@@ -275,6 +275,8 @@ java.savewitherrors.title=Regarding recompile errors
 java.decompiler=Decompiler
 java.targetversion=Compile target version
 java.targetversion.auto=Match class file version
+java.targetdownsampleversion=Downsample target version
+java.targetdownsampleversion.disabled=Disabled
 java.targetdebug=Compile with debug info
 
 ## Search bar
@@ -396,7 +398,8 @@ service.compile=Compilation
 service.compile.java-compiler-config=Javac
 service.compile.java-compiler-config.generate-phantoms=Generate missing classes
 service.compile.java-compiler-config.default-emit-debug=Default to include debug
-service.compile.java-compiler-config.default-target-version=Default to class version
+service.compile.java-compiler-config.default-compile-target-version=Default class version target
+service.compile.java-compiler-config.default-downsample-target-version=Default downsample class version target
 service.debug=Attach/Debug
 service.debug.attach-config=Attach config
 service.debug.attach-config.attach-jmx-bean-agent=Attach JMX bean agent