fix: use correct imports for classes from default package (PR #2031)

* fix: use fully qualified package names for classes of defpackage

* fix: use correct imports for classes from default package (#2027)
---------

Co-authored-by: Skylot <skylot@gmail.com>

jadx-core/src/main/java/jadx/core/codegen/ClassGen.java

@@ -657,6 +657,10 @@ public class ClassGen {
 		if (useCls.equals(extClsInfo)) {
 			return shortName;
 		}
+		if (extClsInfo.getAliasPkg().isEmpty()) {
+			// omit import for default package
+			return shortName;
+		}
 		if (isClassInnerFor(useCls, extClsInfo)) {
 			return shortName;
 		}
@@ -678,10 +682,6 @@ public class ClassGen {
 		if (extClsInfo.getPackage().equals(useCls.getPackage()) && !extClsInfo.isInner()) {
 			return shortName;
 		}
-		// ignore classes from default package
-		if (extClsInfo.isDefaultPackage()) {
-			return shortName;
-		}
 		if (extClsInfo.getAliasPkg().equals(useCls.getAliasPkg())) {
 			fullName = extClsInfo.getAliasNameWithoutPackage();
 		}

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

@@ -0,0 +1,67 @@
+package jadx.tests.integration.names;
+
+import java.util.Collections;
+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 TestDefPkgRename extends SmaliTest {
+
+	@Test
+	public void test() {
+		List<ClassNode> clsList = loadFromSmaliFiles();
+		// class A moved to 'defpackage'
+		assertThat(searchCls(clsList, "A"))
+				.code()
+				.containsOne("package defpackage;");
+		assertThat(searchCls(clsList, "pkg.B"))
+				.code()
+				.containsOne("import defpackage.A;")
+				.containsOne("public A a;");
+	}
+
+	@Test
+	public void testNoImports() {
+		args.setUseImports(false);
+		List<ClassNode> clsList = loadFromSmaliFiles();
+		// class A moved to 'defpackage', but use full names
+		assertThat(searchCls(clsList, "A"))
+				.code()
+				.containsOne("package defpackage;");
+		assertThat(searchCls(clsList, "pkg.B"))
+				.code()
+				.doesNotContain("import")
+				.containsOne("public defpackage.A a;");
+	}
+
+	@Test
+	public void testDeobf() {
+		enableDeobfuscation();
+		List<ClassNode> clsList = loadFromSmaliFiles();
+		// package for class A deobfuscated
+		assertThat(searchCls(clsList, "pkg.B"))
+				.code()
+				.containsOne("import p000.C0000A;")
+				.containsOne("public C0000A f0a;");
+	}
+
+	@Test
+	public void testRenameDisabled() {
+		disableCompilation();
+		args.setRenameFlags(Collections.emptySet());
+		List<ClassNode> clsList = loadFromSmaliFiles();
+		// no renaming, code will not compile
+		assertThat(searchCls(clsList, "A"))
+				.code()
+				.containsOne("// default package");
+		assertThat(searchCls(clsList, "pkg.B"))
+				.code()
+				.doesNotContain("import") // omit import
+				.containsOne("public A a;");
+	}
+}

jadx-core/src/test/smali/names/TestDefPkgRename/a.smali

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

jadx-core/src/test/smali/names/TestDefPkgRename/b.smali

@@ -0,0 +1,4 @@
+.class public Lpkg/B;
+.super Ljava/lang/Object;
+
+.field public a:LA;