fix: resolve class/package name conflicts on case-insensitive filesystems (PR #2828)

* Fix: resolve class/package name conflicts on case-insensitive filesystems

**RenameVisitor**
- Added package-level conflict detection for case-insensitive filesystems:
  when two packages differ only by case (e.g. com.Example vs com.example),
  rename the conflicting one and loop until the new name is also unique
- Added class-level conflict detection (same pattern): when two classes in
  the same package differ only by case (e.g. Sink vs sink), rename the
  conflicting one to prevent file overwrite on Windows export

**Tests**
- Added TestCaseSensitivePkgChecks: verifies package rename when packages
  differ only by case; fixed smali data (2.smali changed Bar→Foo to create
  a genuine path conflict under case-insensitive FS)
- Added TestCaseSensitiveClassInPkgChecks + smali fixtures: verifies class
  rename when two classes in a named package differ only by case
  (com.example.User vs com.example.user)

* Apply suggestions from code review

Co-authored-by: skylot <118523+skylot@users.noreply.github.com>

* Apply suggestions from code review

Co-authored-by: skylot <118523+skylot@users.noreply.github.com>

---------

Co-authored-by: john <johnwsa@qq.com>
Co-authored-by: skylot <118523+skylot@users.noreply.github.com>

jadx-core/src/main/java/jadx/core/dex/visitors/rename/RenameVisitor.java

@@ -59,24 +59,43 @@ public class RenameVisitor extends AbstractVisitor {
 			checkFields(aliasProvider, cls, args);
 			checkMethods(aliasProvider, cls, args);
 		}
+		boolean pkgUpdated = false;
+		for (PackageNode pkg : root.getPackages()) {
+			pkgUpdated |= checkPackage(args, aliasProvider, pkg);
+		}
 		if (!args.isFsCaseSensitive() && args.isRenameCaseSensitive()) {
+			// check for package directory conflicts on case insensitive filesystems
+			Set<String> pkgPaths = new HashSet<>();
+			for (PackageNode pkg : root.getPackages()) {
+				String pkgPath = pkg.getAliasPkgInfo().getFullName().toLowerCase();
+				if (!pkgPaths.add(pkgPath)) {
+					pkg.setLeafAlias(aliasProvider.forPackage(pkg), false);
+					pkgUpdated = true;
+					// verify the new name also doesn't conflict
+					if (!pkgPaths.add(pkg.getAliasPkgInfo().getFullName().toLowerCase())) {
+						pkg.setLeafAlias(aliasProvider.forPackage(pkg), false);
+					}
+				}
+			}
+		}
+		if (pkgUpdated) {
+			root.runPackagesUpdate();
+		}
+		if (!args.isFsCaseSensitive() && args.isRenameCaseSensitive()) {
+			// check for class file conflicts on case insensitive filesystems (run after package rename)
 			Set<String> clsFullPaths = new HashSet<>(classes.size());
 			for (ClassNode cls : classes) {
 				ClassInfo clsInfo = cls.getClassInfo();
 				if (!clsFullPaths.add(clsInfo.getAliasFullPath().toLowerCase())) {
 					clsInfo.changeShortName(aliasProvider.forClass(cls));
 					cls.addAttr(new RenameReasonAttr(cls).append("case insensitive filesystem"));
-					clsFullPaths.add(clsInfo.getAliasFullPath().toLowerCase());
+					// verify the new name also doesn't conflict
+					if (!clsFullPaths.add(clsInfo.getAliasFullPath().toLowerCase())) {
+						clsInfo.changeShortName(aliasProvider.forClass(cls));
+					}
 				}
 			}
 		}
-		boolean pkgUpdated = false;
-		for (PackageNode pkg : root.getPackages()) {
-			pkgUpdated |= checkPackage(args, aliasProvider, pkg);
-		}
-		if (pkgUpdated) {
-			root.runPackagesUpdate();
-		}
 		processRootPackages(aliasProvider, root, classes);
 	}
 

jadx-core/src/test/java/jadx/tests/integration/names/TestCaseSensitiveClassInPkgChecks.java

@@ -0,0 +1,45 @@
+package jadx.tests.integration.names;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestCaseSensitiveClassInPkgChecks extends SmaliTest {
+	/*
+	 * com.example.User and com.example.user - class names differ only by case in the same package.
+	 * On case-insensitive FS both would map to the same file path, requiring class rename.
+	 */
+
+	@Test
+	public void testClassConflictOnCaseInsensitiveFS() {
+		args.setFsCaseSensitive(false);
+
+		List<ClassNode> classes = loadFromSmaliFiles();
+		assertThat(classes).hasSize(2);
+
+		long distinct = classes.stream()
+				.map(cls -> cls.getClassInfo().getAliasFullPath().toLowerCase())
+				.distinct()
+				.count();
+		assertThat(distinct).isEqualTo(2L);
+	}
+
+	@Test
+	public void testClassConflictOnCaseSensitiveFS() {
+		args.setFsCaseSensitive(true);
+
+		List<ClassNode> classes = loadFromSmaliFiles();
+		assertThat(classes).hasSize(2);
+
+		long distinct = classes.stream()
+				.map(cls -> cls.getClassInfo().getAliasFullPath())
+				.distinct()
+				.count();
+		assertThat(distinct).isEqualTo(2L);
+	}
+}

jadx-core/src/test/java/jadx/tests/integration/names/TestCaseSensitivePkgChecks.java

@@ -0,0 +1,48 @@
+package jadx.tests.integration.names;
+
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestCaseSensitivePkgChecks extends SmaliTest {
+	/*
+	 * com.Example.Foo and com.example.Foo - same class name in packages that differ only by case.
+	 * On case-insensitive FS both would map to the same path (com/example/foo), requiring package
+	 * rename.
+	 */
+
+	@Test
+	public void testPkgConflictOnCaseInsensitiveFS() {
+		args.setFsCaseSensitive(false);
+
+		List<ClassNode> classes = loadFromSmaliFiles();
+		assertThat(classes).hasSize(2);
+
+		// all package paths must be distinct when lowercased (no two classes share same dir)
+		long distinctPkgPaths = classes.stream()
+				.map(cls -> cls.getClassInfo().getAliasFullPath().toLowerCase())
+				.distinct()
+				.count();
+		assertThat(distinctPkgPaths).isEqualTo(2L);
+	}
+
+	@Test
+	public void testPkgConflictOnCaseSensitiveFS() {
+		args.setFsCaseSensitive(true);
+
+		List<ClassNode> classes = loadFromSmaliFiles();
+		assertThat(classes).hasSize(2);
+
+		// on case-sensitive FS, original package names should be preserved
+		long distinctPkgPaths = classes.stream()
+				.map(cls -> cls.getClassInfo().getAliasFullPath())
+				.distinct()
+				.count();
+		assertThat(distinctPkgPaths).isEqualTo(2L);
+	}
+}

jadx-core/src/test/smali/names/TestCaseSensitiveClassInPkgChecks/1.smali

@@ -0,0 +1,2 @@
+.class public Lcom/example/User;
+.super Ljava/lang/Object;

jadx-core/src/test/smali/names/TestCaseSensitiveClassInPkgChecks/2.smali

@@ -0,0 +1,2 @@
+.class public Lcom/example/user;
+.super Ljava/lang/Object;

jadx-core/src/test/smali/names/TestCaseSensitivePkgChecks/1.smali

@@ -0,0 +1,2 @@
+.class public Lcom/Example/Foo;
+.super Ljava/lang/Object;

jadx-core/src/test/smali/names/TestCaseSensitivePkgChecks/2.smali

@@ -0,0 +1,2 @@
+.class public Lcom/example/Foo;
+.super Ljava/lang/Object;