Kotlin: explicit accessors for static properties (#1782)

---------- Motivation ----------
Java generator in Gluecodium generates getter/setter methods for static properties.
When such Java code is accessed from Kotlin the methods should be represented as
Kotlin synthetic properties (according to the documentation of Kotlin language).

However, it turns out that such static properties can be also accessed via getter and setter
static functions. Such usage was identified to be working.

Therefore, in order to allow seamless replacement of Java generated code with Kotlin generated
code for Kotlin apps the Kotlin generated code must also allow getting/setting static properties
via getter/setter functions.

---------- Implemented solution ----------
Kotlin generator produces additional extension methods for companion object to allow getting and
setting static properties. The generated methods are annotated as JvmSynthetic to ensure that
they are not visible in Java (because such feature is Kotlin-specific).

Moreover, the value passed to file:JvmName() is adjusted to avoid compilation problems. That name
is used only when we have global functions or properties. Such entities are compiled to the class with
specified name. Because we used the same name as the element defined for given file, when extensions
are defined we would end up with two classes with the same name -- this was adjusted.

Signed-off-by: Patryk Wrobel <[email protected]>

Author: pwrobeldev

.github/workflows/functional-tests.yml

@@ -283,6 +283,8 @@ jobs:
           version: 1.11.0
       - name: Build and run functional tests
         run: |
+          export MACOSX_DEPLOYMENT_TARGET=$(sw_vers -productVersion)
+          export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"
           ./scripts/build-swift-functional --buildGluecodium
         working-directory: functional-tests
       - name: Removing build folder
@@ -291,6 +293,8 @@ jobs:
         working-directory: functional-tests
       - name: Build and run namerules tests
         run: |
+          export MACOSX_DEPLOYMENT_TARGET=$(sw_vers -productVersion)
+          export SDKROOT="$(xcrun --sdk macosx --show-sdk-path)"
           ./scripts/build-swift-namerules --publish
         working-directory: functional-tests
       - name: Build examples

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Unreleased
 ### Features:
  * Kotlin: interfaces are now generated as functional interfaces whenever it is possible.
+ * Kotlin: static properties of classes can be now accessed also via static getter and setter generated as extension function.
 
 ## 13.19.0
 Release date 2025-08-11

functional-tests/functional/android-kotlin/src/test/kotlin/com/here/android/test/AttributesTest.kt

@@ -59,6 +59,12 @@ class AttributesTest {
         assertEquals("fooBar", Attributes.staticAttribute)
     }
 
+    @org.junit.Test
+    fun setGetStaticAttributeViaExplicitFunction() {
+        Attributes.setStaticAttribute("fooBar")
+        assertEquals("fooBar", Attributes.getStaticAttribute())
+    }
+
     @org.junit.Test
     fun getCachedProperty() {
         val instance: CachedProperties = CachedProperties()
@@ -83,6 +89,7 @@ class AttributesTest {
 
         val result1: ByteArray = CachedProperties.staticCachedProperty
         val result2: ByteArray = CachedProperties.staticCachedProperty
+        val result3: ByteArray = CachedProperties.getStaticCachedProperty()
 
         assertEquals(1, CachedProperties.staticCallCount)
 
@@ -93,5 +100,8 @@ class AttributesTest {
 
         assertEquals(result1, result2)
         assertTrue(result1 === result2)
+
+        assertEquals(result1, result3)
+        assertTrue(result1 === result3)
     }
 }

gluecodium/src/main/java/com/here/gluecodium/generator/kotlin/KotlinVisibilityResolver.kt

@@ -28,6 +28,8 @@ import com.here.gluecodium.model.lime.LimeField
 import com.here.gluecodium.model.lime.LimeInterface
 import com.here.gluecodium.model.lime.LimeLambda
 import com.here.gluecodium.model.lime.LimeNamedElement
+import com.here.gluecodium.model.lime.LimeProperty
+import com.here.gluecodium.model.lime.LimeType
 
 internal class KotlinVisibilityResolver(private val referenceMap: Map<String, LimeElement>) : NameResolver {
     override fun resolveName(element: Any): String {
@@ -60,4 +62,33 @@ internal class KotlinVisibilityResolver(private val referenceMap: Map<String, Li
         val parent: LimeElement? = referenceMap[element.path.parent.toString()]
         return parent != null && (parent is LimeInterface || parent is LimeLambda)
     }
+
+    override fun resolveGetterName(element: Any) = resolveVisibilityForPropertyExtension(element)
+
+    override fun resolveSetterName(element: Any) = resolveVisibilityForPropertyExtension(element)
+
+    // Extension method for static properties require explicit 'internal' keyword even when property is nested
+    // inside hierarchy of internal nested types. Therefore, we need to iterate over parent types and check if
+    // any of them is internal.
+    private fun resolveVisibilityForPropertyExtension(property: Any): String {
+        if (property !is LimeProperty) {
+            return ""
+        }
+
+        if (isInternal(property)) {
+            return "internal "
+        }
+
+        val parentElement = referenceMap[property.path.parent.toString()] as LimeNamedElement? ?: return ""
+        if (isInternal(parentElement)) {
+            return "internal "
+        }
+
+        val isEachParentPublic =
+            generateSequence(parentElement) {
+                referenceMap[it.path.parent.toString()] as? LimeType
+            }.none { isInternal(it) }
+
+        return if (isEachParentPublic) "" else "internal "
+    }
 }

gluecodium/src/main/resources/templates/kotlin/KotlinClass.mustache

@@ -155,4 +155,16 @@
 }}{{/thisConstructor}}{{!!
 }}{{/kotlinConstructorExceptions}}{{!!
 
-}}
+}}
+
+{{#ifPredicate "hasStaticProperties"}}
+{{#set classElement=this}}
+{{#properties}}
+{{#if isStatic}}
+{{#set property=this isCached=attributes.cached}}{{#property}}
+{{>kotlin/KotlinStaticPropertyExtension}}
+{{/property}}{{/set}}
+{{/if}}
+{{/properties}}
+{{/set}}
+{{/ifPredicate}}

gluecodium/src/main/resources/templates/kotlin/KotlinFile.mustache

@@ -23,7 +23,7 @@
  *
  */
 
-{{#modelName}}@file:JvmName("{{modelName}}"){{/modelName}}
+{{#modelName}}@file:JvmName("{{modelName}}Extensions"){{/modelName}}
 
 package {{#package}}{{this}}{{#if iter.hasNext}}.{{/if}}{{/package}}
 

gluecodium/src/main/resources/templates/kotlin/KotlinStaticPropertyExtension.mustache

@@ -0,0 +1,32 @@
+{{!!
+  !
+  ! Copyright (C) 2016-2025 HERE Europe B.V.
+  !
+  ! Licensed under the Apache License, Version 2.0 (the "License");
+  ! you may not use this file except in compliance with the License.
+  ! You may obtain a copy of the License at
+  !
+  !     http://www.apache.org/licenses/LICENSE-2.0
+  !
+  ! Unless required by applicable law or agreed to in writing, software
+  ! distributed under the License is distributed on an "AS IS" BASIS,
+  ! WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ! See the License for the specific language governing permissions and
+  ! limitations under the License.
+  !
+  ! SPDX-License-Identifier: Apache-2.0
+  ! License-Filename: LICENSE
+  !
+  !}}
+{{>kotlin/KotlinDocComment}}{{>kotlin/KotlinAttributes}}
+@JvmSynthetic
+{{resolveName this "visibility" "getter"}}fun {{resolveName classElement}}.Companion.{{resolveName this "" "getter"}}(): {{resolveName typeRef}} = {{resolveName classElement}}.{{resolveName this}}{{!!
+}}{{#if setter}}
+
+{{>kotlin/KotlinDocComment}}{{>kotlin/KotlinAttributes}}
+@JvmSynthetic
+{{resolveName this "visibility" "setter"}}fun {{resolveName classElement}}.Companion.{{resolveName this "" "setter"}}(value: {{resolveName typeRef}}) {
+    {{resolveName classElement}}.{{resolveName this}} = value
+}
+
+{{/if}}

gluecodium/src/test/resources/smoke/attributes/output/android-kotlin/com/example/smoke/AttributesClass.kt

@@ -3,7 +3,7 @@
  *
  */
 
-@file:JvmName("AttributesClass")
+@file:JvmName("AttributesClassExtensions")
 
 package com.example.smoke
 

gluecodium/src/test/resources/smoke/attributes/output/android-kotlin/com/example/smoke/AttributesCrashException.kt

@@ -3,7 +3,7 @@
  *
  */
 
-@file:JvmName("AttributesCrash")
+@file:JvmName("AttributesCrashExtensions")
 
 package com.example.smoke
 

gluecodium/src/test/resources/smoke/attributes/output/android-kotlin/com/example/smoke/AttributesEnum.kt

@@ -3,7 +3,7 @@
  *
  */
 
-@file:JvmName("AttributesEnum")
+@file:JvmName("AttributesEnumExtensions")
 
 package com.example.smoke