Fix 'switch' codegen for empty case block

src/main/java/jadx/codegen/CodeWriter.java

@@ -36,6 +36,13 @@ public class CodeWriter {
 		return this;
 	}
 
+	public CodeWriter startLine(char c) {
+		buf.append(NL);
+		buf.append(indentStr);
+		buf.append(c);
+		return this;
+	}
+
 	public CodeWriter startLine(int ind, String str) {
 		buf.append(NL);
 		buf.append(indentStr);

src/main/java/jadx/codegen/RegionGen.java

@@ -107,7 +107,7 @@ public class RegionGen extends InsnGen {
 		IfNode insn = region.getIfInsn();
 		code.add("if ").add(makeCondition(insn)).add(" {");
 		makeRegionIndent(code, region.getThenRegion());
-		code.startLine("}");
+		code.startLine('}');
 
 		IContainer els = region.getElseRegion();
 		if (els != null && RegionUtils.notEmpty(els)) {
@@ -123,11 +123,11 @@ public class RegionGen extends InsnGen {
 				}
 			}
 
-			code.add("{");
+			code.add('{');
 			code.incIndent();
 			makeRegion(code, els);
 			code.decIndent();
-			code.startLine("}");
+			code.startLine('}');
 		}
 	}
 
@@ -136,7 +136,7 @@ public class RegionGen extends InsnGen {
 			// infinite loop
 			code.startLine("while (true) {");
 			makeRegionIndent(code, region.getBody());
-			code.startLine("}");
+			code.startLine('}');
 			return code;
 		}
 
@@ -144,11 +144,11 @@ public class RegionGen extends InsnGen {
 		if (!region.isConditionAtEnd()) {
 			code.startLine("while ").add(makeCondition(insn)).add(" {");
 			makeRegionIndent(code, region.getBody());
-			code.startLine("}");
+			code.startLine('}');
 		} else {
 			code.startLine("do {");
 			makeRegionIndent(code, region.getBody());
-			code.startLine("} while ").add(makeCondition(insn)).add(";");
+			code.startLine("} while ").add(makeCondition(insn)).add(';');
 		}
 		return code;
 	}
@@ -156,7 +156,7 @@ public class RegionGen extends InsnGen {
 	private void makeSynchronizedRegion(SynchronizedRegion cont, CodeWriter code) throws CodegenException {
 		code.startLine("synchronized(").add(arg(cont.getArg())).add(") {");
 		makeRegionIndent(code, cont.getRegion());
-		code.startLine("}");
+		code.startLine('}');
 	}
 
 	private String makeCondition(IfNode insn) throws CodegenException {
@@ -194,25 +194,37 @@ public class RegionGen extends InsnGen {
 			List<Integer> keys = sw.getKeys().get(i);
 			IContainer c = sw.getCases().get(i);
 			for (Integer k : keys) {
-				code.startLine("case ")
-						.add(TypeGen.literalToString(k, arg.getType()))
-						.add(":");
+				code.startLine("case ");
+				code.add(TypeGen.literalToString(k, arg.getType()));
+				code.add(':');
 			}
-			makeRegionIndent(code, c);
-			if (RegionUtils.hasExitEdge(c))
-				code.startLine(1, "break;");
+			makeCaseBlock(c, code);
 		}
 		if (sw.getDefaultCase() != null) {
 			code.startLine("default:");
-			makeRegionIndent(code, sw.getDefaultCase());
-			if (RegionUtils.hasExitEdge(sw.getDefaultCase()))
-				code.startLine(1, "break;");
+			makeCaseBlock(sw.getDefaultCase(), code);
 		}
 		code.decIndent();
-		code.startLine("}");
+		code.startLine('}');
 		return code;
 	}
 
+	private void makeCaseBlock(IContainer c, CodeWriter code) throws CodegenException {
+		if (RegionUtils.notEmpty(c)) {
+			boolean closeBlock = RegionUtils.hasExitEdge(c);
+			if (closeBlock) {
+				code.add(" {");
+			}
+			makeRegionIndent(code, c);
+			if (closeBlock) {
+				code.startLine(1, "break;");
+				code.startLine('}');
+			}
+		} else {
+			code.startLine(1, "break;");
+		}
+	}
+
 	private void makeTryCatch(IContainer region, TryCatchBlock tryCatchBlock, CodeWriter code)
 			throws CodegenException {
 		code.startLine("try {");
@@ -235,7 +247,7 @@ public class RegionGen extends InsnGen {
 			code.startLine("} finally {");
 			makeRegionIndent(code, tryCatchBlock.getFinalBlock());
 		}
-		code.startLine("}");
+		code.startLine('}');
 	}
 
 	private void makeCatchBlock(CodeWriter code, ExceptionHandler handler)

src/main/java/jadx/dex/visitors/ModVisitor.java

@@ -148,10 +148,13 @@ public class ModVisitor extends AbstractVisitor {
 						break;
 
 					case RETURN:
-						if (insn.getArgsCount() == 0
-								&& mth.getBasicBlocks().size() == 1
-								&& i == size - 1)
+						if (insn.getArgsCount() == 0) {
+							if (mth.getBasicBlocks().size() == 1 && i == size - 1) {
+								remover.add(insn);
+							} else if (mth.getMethodInfo().isClassInit()) {
 								remover.add(insn);
+							}
+						}
 						break;
 
 					default:

src/main/java/jadx/dex/visitors/regions/RegionMaker.java

@@ -404,7 +404,6 @@ public class RegionMaker {
 		}
 
 		Map<BlockNode, List<Integer>> blocksMap = new LinkedHashMap<BlockNode, List<Integer>>(len);
-
 		for (Entry<Integer, List<Integer>> entry : casesMap.entrySet()) {
 			BlockNode c = BlockUtils.getBlockByOffset(entry.getKey(), block.getSuccessors());
 			assert c != null;
@@ -413,7 +412,7 @@ public class RegionMaker {
 
 		BitSet succ = BlockUtils.blocksToBitSet(mth, block.getSuccessors());
 		BitSet domsOn = BlockUtils.blocksToBitSet(mth, block.getDominatesOn());
-		domsOn.andNot(succ); // filter 'out' block
+		domsOn.and(succ); // filter 'out' block
 
 		BlockNode defCase = BlockUtils.getBlockByOffset(insn.getDefaultCaseOffset(), block.getSuccessors());
 		if (defCase != null) {
@@ -458,8 +457,13 @@ public class RegionMaker {
 		}
 		for (Entry<BlockNode, List<Integer>> entry : blocksMap.entrySet()) {
 			BlockNode c = entry.getKey();
+			if (stack.containsExit(c)) {
+				// empty case block
+				sw.addCase(entry.getValue(), new Region(stack.peekRegion()));
+			} else {
 				sw.addCase(entry.getValue(), makeRegion(c, stack));
 			}
+		}
 
 		stack.pop();
 		return out;

src/samples/java/jadx/samples/AbstractTest.java

@@ -15,4 +15,13 @@ public abstract class AbstractTest {
 			throw new AssertionError(a1 + " != " + a2);
 		}
 	}
+
+	public static void assertEquals(Object a1, Object a2) {
+		if (a1 == null) {
+			if (a2 != null)
+				throw new AssertionError(a1 + " != " + a2);
+		} else if (!a1.equals(a2)) {
+			throw new AssertionError(a1 + " != " + a2);
+		}
+	}
 }

src/samples/java/jadx/samples/TestSwitch.java

@@ -78,13 +78,43 @@ public class TestSwitch extends AbstractTest {
 		return -1;
 	}
 
+	public String escape(String str) {
+		int len = str.length();
+		StringBuilder sb = new StringBuilder(len);
+		for (int i = 0; i < len; i++) {
+			char c = str.charAt(i);
+			switch (c) {
+				case '.':
+				case '/':
+					sb.append('_');
+					break;
+
+				case ']':
+					sb.append('A');
+					break;
+
+				case '?':
+					break;
+
+				default:
+					sb.append(c);
+					break;
+			}
+		}
+		return sb.toString();
+	}
+
 	@Override
 	public boolean testRun() {
 		assertTrue(test1(25) == 2);
 		assertTrue(test2(5) == 3);
 		assertTrue(test3(1, 0) == 0);
 		assertTrue(test4(2) == 1);
+		assertEquals(escape("a.b/c]d?e"), "a_b_cAde");
 		return true;
 	}
 
+	public static void main(String[] args) {
+		new TestSwitch().testRun();
+	}
 }