Preserve original NSString in kotlin.String if possible

Thus fix localized strings in Kotlin.

backend.native/tests/build.gradle

@@ -3565,6 +3565,11 @@ interopTest("interop_objc_smoke") {
         if (project.target instanceof KonanTarget.IOS_X64) {
             UtilsKt.codesign(project, "$buildDir/libobjcsmoke.dylib")
         }
+
+        copy {
+            from("interop/objc/Localizable.stringsdict")
+            into("$testOutputLocal/$name/$target/en.lproj/")
+        }
     }
 }
 

backend.native/tests/framework/values/values.swift

@@ -1078,16 +1078,41 @@ func testGH3525() throws {
 }
 
 func testStringConversion() throws {
-    let test = TestStringConversion()
+    func test1() throws {
+        let test = TestStringConversion()
 
-    let buffer = NSMutableString()
-    buffer.append("a")
-    test.str = buffer
-    buffer.append("b")
+        let buffer = NSMutableString()
+        buffer.append("a")
+        test.str = buffer
+        buffer.append("b")
 
-    try assertEquals(actual: buffer, expected: "ab")
-    // Ensure test.str isn't affected by buffer mutation:
-    try assertEquals(actual: test.str as! NSString, expected: "a")
+        try assertEquals(actual: buffer, expected: "ab")
+        // Ensure test.str isn't affected by buffer mutation:
+        try assertEquals(actual: test.str as! NSString, expected: "a")
+    }
+
+    func ensureNoCopy(nsStr: NSString) throws {
+        let test = TestStringConversion()
+
+        test.str = nsStr
+        let nsStr2 = test.str as! NSString
+
+        // Ensure no additional NSString created on both conversions:
+        try assertTrue(nsStr === nsStr2)
+    }
+
+    func test2() throws {
+        var str = "a"
+        str += NSObject().description
+        try ensureNoCopy(nsStr: str as NSString)
+
+        try ensureNoCopy(nsStr: NSString("abc"))
+
+        try ensureNoCopy(nsStr: NSString(format: "%d%d%d", 3, 2, 1))
+    }
+
+    try test1()
+    try test2()
 }
 
 // -------- Execution of the test --------

backend.native/tests/interop/objc/Localizable.stringsdict

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- AUTO-GENERATED FILE. DO NOT MODIFY. -->
+<!-- This file was automatically generated by the LocoLaser tool. -->
+<!-- It should not be modified by hand. -->
+
+<plist version="1.0">
+    <dict>
+        <key>screen_main_plural_string</key>
+        <dict>
+            <key>NSStringLocalizedFormatKey</key>
+            <string>%#@value@</string>
+            <key>value</key>
+            <dict>
+                <key>NSStringFormatSpecTypeKey</key>
+                <string>NSStringPluralRuleType</string>
+                <key>NSStringFormatValueTypeKey</key>
+                <string>d</string>
+                <key>other</key>
+                <string>Plural: %d apples</string>
+                <key>one</key>
+                <string>Plural: one apple</string>
+                <key>zero</key>
+                <string>Plural: no apples</string>
+            </dict>
+        </dict>
+    </dict>
+</plist>

backend.native/tests/interop/objc/objcSmoke.def

@@ -1,4 +1,4 @@
 language = Objective-C
-headers = Foundation/NSArray.h Foundation/NSValue.h Foundation/NSString.h Foundation/NSStream.h
+headers = Foundation/NSArray.h Foundation/NSValue.h Foundation/NSString.h Foundation/NSStream.h Foundation/NSBundle.h
 headerFilter = **/smoke.h Foundation/NSArray.h Foundation/NSValue.h Foundation/NSString.h Foundation/NSStream.h \
-    objc/objc.h
+    objc/objc.h Foundation/NSBundle.h

backend.native/tests/interop/objc/smoke.h

@@ -224,3 +224,18 @@ Protocol* getPrinterProtocol() {
 @interface TestAllocNoRetain : NSObject
 @property BOOL ok;
 @end;
+
+@interface CustomString : NSString
+- (instancetype)initWithValue:(int)value;
+@property int value;
+@end;
+
+CustomString* _Nonnull createCustomString(int value) {
+    return [[CustomString alloc] initWithValue:value];
+}
+
+int getCustomStringValue(CustomString* str) {
+    return str.value;
+}
+
+extern BOOL customStringDeallocated;

backend.native/tests/interop/objc/smoke.kt

@@ -29,6 +29,8 @@ fun run() {
     testAllocNoRetain()
     testNSOutputStreamToMemoryConstructor()
     testExportObjCClass()
+    testCustomString()
+    testLocalizedStrings()
 
     assertEquals(2, ForwardDeclaredEnum.TWO.value)
 
@@ -457,6 +459,28 @@ fun testExportObjCClass() {
             xor (TestExportObjCClass4().objCClassName == TestExportObjCClass34Name))
 }
 
+fun testCustomString() {
+    assertFalse(customStringDeallocated)
+
+    fun test() = autoreleasepool {
+        val str: String = createCustomString(321)
+        assertEquals("321", str)
+        assertEquals("CustomString", str.objCClassName)
+        assertEquals(321, getCustomStringValue(str))
+    }
+
+    test()
+    kotlin.native.internal.GC.collect()
+    assertTrue(customStringDeallocated)
+}
+
+fun testLocalizedStrings() {
+    val key = "screen_main_plural_string"
+    val localizedString = NSBundle.mainBundle.localizedStringForKey(key, value = "", table = "Localizable")
+    val string = NSString.localizedStringWithFormat(localizedString, 5)
+    assertEquals("Plural: 5 apples", string)
+}
+
 private val Any.objCClassName: String
     get() = object_getClassName(this)!!.toKString()
 

backend.native/tests/interop/objc/smoke.m

@@ -289,3 +289,34 @@ static CustomRetainMethodsImpl* retainedCustomRetainMethodsImpl;
     return self;
 }
 @end;
+
+BOOL customStringDeallocated = NO;
+
+@implementation CustomString {
+    NSString* delegate;
+}
+
+- (instancetype)initWithValue:(int)value {
+    if (self = [super init]) {
+        self->delegate = @(value).description;
+        self.value = value;
+    }
+    return self;
+}
+
+- (unichar)characterAtIndex:(NSUInteger)index {
+    return [self->delegate characterAtIndex:index];
+}
+
+- (NSUInteger)length {
+    return self->delegate.length;
+}
+
+- (id)copyWithZone:(NSZone *)zone {
+    return self;
+}
+
+- (void)dealloc {
+    customStringDeallocated = YES;
+}
+@end;

runtime/src/main/cpp/ObjCInteropUtils.mm

@@ -19,6 +19,7 @@
 #if KONAN_OBJC_INTEROP
 
 #import <objc/runtime.h>
+#import <CoreFoundation/CFString.h>
 #import <Foundation/NSException.h>
 #import <Foundation/NSString.h>
 #import "Memory.h"
@@ -69,12 +70,16 @@ OBJ_GETTER(Kotlin_Interop_CreateKStringFromNSString, NSString* str) {
     RETURN_OBJ(nullptr);
   }
 
-  size_t length = [str length];
-  NSRange range = {0, length};
+  CFStringRef immutableCopyOrSameStr = CFStringCreateCopy(nullptr, (CFStringRef)str);
+
+  auto length = CFStringGetLength(immutableCopyOrSameStr);
+  CFRange range = {0, length};
   ArrayHeader* result = AllocArrayInstance(theStringTypeInfo, length, OBJ_RESULT)->array();
   KChar* rawResult = CharArrayAddressOfElementAt(result, 0);
 
-  [str getCharacters:rawResult range:range];
+  CFStringGetCharacters(immutableCopyOrSameStr, range, rawResult);
+
+  result->obj()->meta_object()->associatedObject_ = (void*)immutableCopyOrSameStr;
 
   RETURN_OBJ(result->obj());
 }