New J2K: remove initializer from property without backing field

#KT-33637 fixed

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/JKInMemoryFilesSearcher.kt

@@ -12,7 +12,7 @@ import com.intellij.psi.search.searches.ReferencesSearch
 import org.jetbrains.kotlin.psi.KtElement
 
 internal abstract class JKInMemoryFilesSearcher {
-    abstract fun search(element: KtElement): Iterable<PsiReference>
+    abstract fun search(element: KtElement, scope: PsiElement? = null): Iterable<PsiReference>
 
     companion object {
         fun create(files: List<PsiElement>) = when {
@@ -23,8 +23,8 @@ internal abstract class JKInMemoryFilesSearcher {
 }
 
 internal class JKSingleFileInMemoryFilesSearcher(private val scopeElement: PsiElement) : JKInMemoryFilesSearcher() {
-    override fun search(element: KtElement): Iterable<PsiReference> =
-        ReferencesSearch.search(element, LocalSearchScope(scopeElement))
+    override fun search(element: KtElement, scope: PsiElement?): Iterable<PsiReference> =
+        ReferencesSearch.search(element, LocalSearchScope(scope ?: scopeElement))
 }
 
 
@@ -32,7 +32,10 @@ internal class JKSingleFileInMemoryFilesSearcher(private val scopeElement: PsiEl
 // maybe the solution is to do searching manually
 // firstly by-text and then resolving
 internal class JKMultipleFilesInMemoryFilesSearcher(private val scopeElements: List<PsiElement>) : JKInMemoryFilesSearcher() {
-    override fun search(element: KtElement): Iterable<PsiReference> {
+    override fun search(element: KtElement, scope: PsiElement?): Iterable<PsiReference> {
+        if (scope != null) {
+            return ReferencesSearch.search(element, LocalSearchScope(scope))
+        }
         val result = mutableListOf<PsiReference>()
         for (scopeElement in scopeElements) {
             result += ReferencesSearch.search(element, LocalSearchScope(scopeElement))

nj2k/nj2k-services/src/org/jetbrains/kotlin/nj2k/postProcessing/processings/ConvertGettersAndSettersToPropertyProcessing.kt

@@ -120,7 +120,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
         val name = name?.asGetterName() ?: return null
         if (valueParameters.isNotEmpty()) return null
         if (typeParameters.isNotEmpty()) return null
-        val target = bodyExpression
+        val singleTimeUsedTarget = bodyExpression
             ?.statements()
             ?.singleOrNull()
             ?.safeAs<KtReturnExpression>()
@@ -129,7 +129,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
             ?.takeIf {
                 it.type() == type() ?: return@takeIf false
             }
-        return RealGetter(this, target, name)
+        return RealGetter(this, singleTimeUsedTarget, name, singleTimeUsedTarget != null)
     }
 
     private fun KtNamedFunction.asSetter(): Setter? {
@@ -138,7 +138,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
         if (valueParameters.size != 1) return null
         val descriptor = resolveToDescriptorIfAny() ?: return null
         if (descriptor.returnType?.isUnit() != true) return null
-        val target = bodyExpression
+        val singleTimeUsedTarget = bodyExpression
             ?.statements()
             ?.singleOrNull()
             ?.let { expression ->
@@ -151,7 +151,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
             }?.takeIf {
                 it.type() == valueParameters.single().type()
             }
-        return RealSetter(this, target, name)
+        return RealSetter(this, singleTimeUsedTarget, name, singleTimeUsedTarget != null)
     }
 
     private fun KtDeclaration.asPropertyAccessor(): PropertyInfo? {
@@ -262,18 +262,17 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
             else -> false
         }
 
-    private fun KtElement.usages() =
-        searcher.search(this)
+    private fun KtElement.usages(scope: PsiElement? = null) =
+        searcher.search(this, scope)
 
     private fun <T : KtExpression> T.withReplacedExpressionInBody(
         from: KtElement,
         to: KtExpression,
         replaceOnlyWriteUsages: Boolean
     ): T = also {
-        from.usages()
+        from.usages(this)
             .asSequence()
             .map { it.element }
-            .filter { it.isInsideOf(listOf(this)) }
             .forEach { reference ->
                 val parent = reference.parent
                 val referenceExpression = when {
@@ -343,6 +342,14 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
         return calculatePropertyType(getterType, setterType)
     }
 
+    private inline fun <reified A : RealAccessor> A.withTargetSet(property: RealProperty?): A {
+        if (property == null) return this
+        if (target != null) return this
+        return if(property.property.usages(function).any())
+            updateTarget(property.property) as A
+        else this
+    }
+
     private fun KtClassOrObject.collectPropertiesData(collectingState: CollectingState): List<PropertyData> {
         return declarations
             .asSequence()
@@ -382,7 +389,13 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
                         realSetter?.function
                     ) ?: return@mapNotNull null
                 collectingState.propertyNameToSuperType[this to name] = type
-                PropertyData(realProperty, realGetter, realSetter, type)
+
+                PropertyData(
+                    realProperty,
+                    realGetter?.withTargetSet(realProperty),
+                    realSetter?.withTargetSet(realProperty),
+                    type
+                )
             }
     }
 
@@ -441,7 +454,7 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
                 ) return@mapNotNull null
             }
 
-            if (realProperty != null && (realGetter != null && realGetter.target == null || realSetter != null && realSetter.target == null)) {
+            if (realProperty != null && (realGetter != null && !realGetter.isPure || realSetter != null && !realSetter.isPure)) {
                 if (!realProperty.property.isPrivate()) return@mapNotNull null
                 val hasUsages =
                     realProperty.property.hasUsagesOutsideOf(
@@ -627,6 +640,12 @@ private class ConvertGettersAndSettersToPropertyStatefulProcessing(
                 commentSaver.restore(ktProperty)
             }
 
+            // If getter & setter do not have backing fields we should remove initializer
+            // As we already know that property is not directly used in the code
+            if (getter.target == null && setter?.target == null) {
+                ktProperty.initializer = null
+            }
+
             val propertyVisibility = ktProperty.visibilityModifierTypeOrDefault()
             getterVisibility?.let { ktProperty.setVisibility(it) }
             if (ktSetter != null) {
@@ -707,15 +726,19 @@ private interface RealAccessor : Accessor {
         get() = function.bodyExpression
     override val modifiersText: String
         get() = function.modifierList?.text.orEmpty()
-    override val isPure: Boolean
-        get() = target != null
+
+    fun updateTarget(newTarget: KtProperty): RealAccessor
 }
 
 private data class RealGetter(
     override val function: KtNamedFunction,
     override val target: KtProperty?,
-    override val name: String
-) : Getter(), RealAccessor
+    override val name: String,
+    override val isPure: Boolean
+) : Getter(), RealAccessor {
+    override fun updateTarget(newTarget: KtProperty): RealGetter =
+        copy(target = newTarget)
+}
 
 private data class FakeGetter(
     override val name: String,
@@ -726,10 +749,14 @@ private data class FakeGetter(
 private data class RealSetter(
     override val function: KtNamedFunction,
     override val target: KtProperty?,
-    override val name: String
+    override val name: String,
+    override val isPure: Boolean
 ) : Setter(), RealAccessor {
     override val parameterName: String
         get() = (function.valueParameters.first().name ?: name).fixSetterParameterName()
+
+    override fun updateTarget(newTarget: KtProperty): RealSetter =
+        copy(target = newTarget)
 }
 
 private data class FakeSetter(

nj2k/testData/newJ2k/detectProperties/NoBackingField.java

@@ -0,0 +1,7 @@
+public class Host {
+    private String name;
+
+    public String getName() {
+        return "Name";
+    }
+}

nj2k/testData/newJ2k/detectProperties/NoBackingField.kt

@@ -0,0 +1,4 @@
+class Host {
+    val name: String?
+        get() = "Name"
+}

nj2k/tests/org/jetbrains/kotlin/nj2k/NewJavaToKotlinConverterSingleFileTestGenerated.java

@@ -1585,6 +1585,11 @@ public class NewJavaToKotlinConverterSingleFileTestGenerated extends AbstractNew
             runTest("nj2k/testData/newJ2k/detectProperties/kt-32253.java");
         }
 
+        @TestMetadata("NoBackingField.java")
+        public void testNoBackingField() throws Exception {
+            runTest("nj2k/testData/newJ2k/detectProperties/NoBackingField.java");
+        }
+
         @TestMetadata("Overrides.java")
         public void testOverrides() throws Exception {
             runTest("nj2k/testData/newJ2k/detectProperties/Overrides.java");