[KT-48068] Add opt-in support for NSEnum for Kotlin Native iOS via an annotation #5539

stefanhaustein · 2025-10-29T18:22:49Z

Basically implementing the feature suggested here: https://youtrack.jetbrains.com/issue/KT-48068

…ator

SvyatoslavScherbina · 2025-10-30T17:09:21Z

/test-private

kotlin-safe-merge · 2025-10-30T17:09:26Z

Failed to process command due to an unexpected exception.

native/objcexport-header-generator/src/org/jetbrains/kotlin/backend/konan/objcexport/stubs.kt

native/native.tests/testData/framework/objcexport/nativeEnum.kt

kotlin-native/runtime/src/main/kotlin/kotlin/native/Annotations.kt

...-generator/impl/k1/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslator.kt

...er/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportCodeSpec.kt

...bjcexport-header-generator/src/org/jetbrains/kotlin/backend/konan/objcexport/StubRenderer.kt

SvyatoslavScherbina · 2025-10-31T12:41:03Z

The K2 (Analysis API, aka AA) implementation is missing, which makes the new test fail in this mode.
Run

./gradlew :native:objcexport-header-generator:testAnalysisApi --tests "org.jetbrains.kotlin.backend.konan.tests.ObjCExportHeaderGeneratorTest"

to reproduce.

Related code:

kotlin/native/objcexport-header-generator/impl/analysis-api/src/org/jetbrains/kotlin/objcexport/translateToObjCClass.kt

Line 54 in f90cbf3

this += translateEnumMembers(symbol)

SvyatoslavScherbina · 2025-10-31T12:45:21Z

Another thing to fix: adding a declaration to stdlib requires updating the ABI dump.
Run the following command to do that:

./gradlew :tools:binary-compatibility-validator:cleanTest :tools:binary-compatibility-validator:test --tests "*" -Poverwrite.output=true

stefanhaustein · 2025-11-04T13:27:01Z

The K2 (Analysis API, aka AA) implementation is missing, which makes the new test fail in this mode. Run

I have added this, but AA emits the a comment about the annotation whereas K1 does not... Any suggestions how to resolve this? Current state is the AA output

…mment

…g K1

SvyatoslavScherbina · 2025-11-04T12:51:17Z

...end.native/src/org/jetbrains/kotlin/backend/konan/llvm/objcexport/ObjCExportCodeGenerator.kt

+        methodBridge: MethodBridge,
+        selectorName: String
+): ObjCToKotlinMethodAdapter {
+    val imp = generateObjCImp(symbol.owner, symbol.owner.getLowered<IrSimpleFunction>(), methodBridge)


I think both symbol.owner usages here should be getLowered. The first two arguments of generateObjCImp are supposed to be consistent – either the same function or two functions, one overriding another.

SvyatoslavScherbina · 2025-11-17T12:53:10Z

...end.native/src/org/jetbrains/kotlin/backend/konan/llvm/objcexport/ObjCExportCodeGenerator.kt

 import org.jetbrains.kotlin.backend.konan.lower.getLoweredConstructorFunction
 import org.jetbrains.kotlin.backend.konan.lower.getObjectClassInstanceFunction
 import org.jetbrains.kotlin.backend.konan.objcexport.*
+import org.jetbrains.kotlin.backend.konan.objcexport.ObjCMethodSpec.BaseMethod


Unused import?

SvyatoslavScherbina · 2025-11-17T12:55:29Z

...end.native/src/org/jetbrains/kotlin/backend/konan/llvm/objcexport/ObjCExportCodeGenerator.kt

                adapters += createConstructorAdapter(it.baseMethod)
            }
+            is ObjCGetterForNSEnumType -> {
+                adapters += createNSEnumAdapter(it.symbol, it.bridge, it. selector)


Redundant space in it. selector.

SvyatoslavScherbina · 2025-11-17T13:10:46Z

...er/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportCodeSpec.kt

            if (descriptor.kind == ClassKind.ENUM_CLASS) {
+                if (namer.getNSEnumFunctionTypeName(descriptor) != null) {
+                    val superClass = descriptor.getSuperClassNotAny()!!  // ordinal is declared in KotlinEnum
+                    val ordinalDescriptor = superClass.contributedMethods.first { it.name.asString() == "<get-ordinal>" }


A little bit less magical way to do that would be:

superClass.contributedMethods.first { it.propertyIfAccessor.name.asString() == "ordinal" }

or

superClass.unsubstitutedMemberScope.getContributedVariables(Name.identifier("ordinal"), NoLookupLocation.FROM_BACKEND).single().getter

SvyatoslavScherbina · 2025-11-17T13:19:01Z

...er/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportCodeSpec.kt

            is ObjCInitMethodForKotlinConstructor -> "$objcClass.${baseMethod.selector},${baseMethod.symbol.signature}"
            is ObjCKotlinThrowableAsErrorMethod -> null
            is ObjCMethodForKotlinMethod -> "$objcClass.${baseMethod.selector},${baseMethod.symbol.signature}"
+            is ObjCGetterForNSEnumType -> "$objcClass.$selector,${symbol.signature}"


Now, that's a bit tricky.
IIRC, the dump generated here is used for some additional DCE: if the Objective-C/Swift code doesn't use certain generated method, using this dump we can find the original Kotlin declaration that doesn't need to be exposed then.

The problem with this implementation is therefore the following: if the generated nsEnum property of a class is not used, the compiler will be instructed to hide Enum.ordinal, which is not exactly intended.

See these changes for more details:

6473bc5

9ef93a1

SvyatoslavScherbina · 2025-11-17T14:10:34Z

...-generator/impl/k1/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslator.kt

+    val objCInterface: ObjCInterface,
+)
+
+fun TranslatedClass(objCInterface: ObjCInterface) = TranslatedClass(emptyList(), objCInterface)


A separate function is not really necessary – we can simply add a default argument to the TranslatedClass constructor:

class TranslatedClass( val auxiliaryDeclarations: List<ObjCExportStub> = emptyList(), val objCInterface: ObjCInterface, )

SvyatoslavScherbina · 2025-11-17T14:12:33Z

...-generator/impl/k1/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslator.kt

                    val type = mapType(descriptor.defaultType, ReferenceBridge, ObjCRootExportScope)

+                    namer.getNSEnumFunctionTypeName(descriptor)?.let { nsEnumTypeName ->
+                        // Map the enum entries in declaration order, preserving the ordinal


Ordering here is tricky.

I mean, I couldn't find anything in the KDocs that would mention that it preserves the declaration order. Neither for K1, nor for AA.
Moreover, not many things rely on the declaration order here, and certain parts of the compiler perform alphabetical sorting.

In other words, relying on a specific order here might be fragile. Let's address it the following way: in tests (native/objcexport-header-generator/testData/headers as well as native/native.tests/testData/framework/objcexport), make enum entries have a non-alphabetical order.
So that, if someone starts sorting them alphabetically elsewhere in the compiler, the test will catch that.

SvyatoslavScherbina · 2025-11-17T14:15:40Z

...-generator/impl/k1/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslator.kt

+                superProtocols = superProtocols,
+                members = members,
+                attributes = attributes,
+                comment = objCCommentOrNull(mustBeDocumentedAttributeList(descriptor.annotations))))


The general convention in Kotlin is to put the closing ) on a new line whenever the opening ( is on a different line.

SvyatoslavScherbina · 2025-11-17T15:04:38Z

native/objcexport-header-generator/src/org/jetbrains/kotlin/backend/konan/objcexport/stubs.kt


 abstract class ObjCTopLevel : ObjCExportStub

+class ObjCNSEnum(


It would be reasonable to make it also have an explicit Swift name using the swift_name attribute, just like it is done for the rest of the declaration classes.

SvyatoslavScherbina · 2025-11-17T15:14:21Z

...-generator/impl/k1/src/org/jetbrains/kotlin/backend/konan/objcexport/ObjCExportTranslator.kt

+                                listOf("readonly"),
+                                declarationAttributes = emptyList(),
+                                comment = null)
+                        }


If the enum already has a property named nsEnum, we'll get a name conflict here.
I don't propose fixing this (as it would be unreasonably complicated), so let's meaningfully postpone it:
please create a new issue (https://youtrack.jetbrains.com/newIssue?project=KT) for this problem.
And also add a // TODO here mentioning that issue, so that the next person reading this code won't need to think about that.

stefanhaustein added 14 commits September 29, 2025 13:48

make 'something' visible end-to-end

2ab6493

End-to-end wireup with test; method body missing

b824f55

current state (incomplete)

e180ad4

cleanup

6ab07ae

cleanup

b925ff2

cleanup

e7ec42e

ordinal should be in KotlinEnum

7e4fb66

refactored to avoid ObjCMethodForKotlinMethod

b713914

move symbol resolution from ObjCExportCodeSpec to ObjCExportCodeGener…

b126cd4

…ator

swift test compiles

f51d934

remove footgun

854371f

objc/switft name distinction / adjustment

4013372

Merge branch 'JetBrains:master' into master

c9de8d8

Merge branch 'JetBrains:master' into master

200acce

stefanhaustein requested review from a team, DmitryNekrasov, fzhinkin, ilya-g and qwwdfsad as code owners October 29, 2025 18:22

stefanhaustein requested review from SvyatoslavScherbina and vsukharev October 29, 2025 18:22

SvyatoslavScherbina reviewed Oct 30, 2025

View reviewed changes

first round of review comments / snapshot before changing to property

29e8031

stefanhaustein changed the title ~~Add opt-in support for NSEnum for Kotlin Native iOS via an annotation~~ [KT-48068] Add opt-in support for NSEnum for Kotlin Native iOS via an annotation Nov 4, 2025

Merge branch 'JetBrains:master' into master

de01982

Review comments addressed; mostly adding the missing AA impl

0ccc118

stefanhaustein requested a review from a team as a code owner November 4, 2025 13:21

stefanhaustein added 3 commits November 5, 2025 16:27

Make the enum entry value / order more explicit / add a clarifying co…

60cca82

…mment

Naming consistency / fixes and test extensions / improvements

8da8bb4

Move ObjCEnum to the auto documentartion exclude list for AA, matchin…

6a52203

…g K1

stefanhaustein requested a review from SvyatoslavScherbina November 13, 2025 18:10

SvyatoslavScherbina reviewed Nov 17, 2025

View reviewed changes

first part of addressing 2nd round of review comments

bfb6921


		abstract class ObjCTopLevel : ObjCExportStub

		class ObjCNSEnum(

[KT-48068] Add opt-in support for NSEnum for Kotlin Native iOS via an annotation #5539

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[KT-48068] Add opt-in support for NSEnum for Kotlin Native iOS via an annotation #5539

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stefanhaustein commented Oct 29, 2025

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SvyatoslavScherbina commented Oct 30, 2025

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