fix: EXPOSED-704 ClassCastException when referencing an eager-loaded …

…backReferencedOn with keepLoadedReferencesOutOfTransaction = true Both BackReference and OptionalBackReference classes use Referrers as their delegate class when getValue() is invoked. This means that, when there is no transaction context, the delegate correctly attempts to get a child value from the cache, but incorrectly assumes it will be a SizedIterable (normal for Referrers). This ensures that an attempt is made to store the child value as a LazySizedCollection if it is not found to be a collection itself already.
JetBrains · Jan 31, 2025 · 256a381 · 256a381
1 parent 7e3a92e
commit 256a381
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Showing 3 changed files with 9 additions and 3 deletions.
diff --git a/exposed-dao/src/main/kotlin/org/jetbrains/exposed/dao/References.kt b/exposed-dao/src/main/kotlin/org/jetbrains/exposed/dao/References.kt
@@ -154,7 +154,10 @@ open class Referrers<ParentID : Any, in Parent : Entity<ParentID>, ChildID : Any
         }
         val transaction = TransactionManager.currentOrNull()
         return when {
-            transaction == null -> thisRef.getReferenceFromCache(reference)
+            transaction == null -> {
+                val cachedValue = thisRef.getReferenceFromCache<Any?>(reference)
+                cachedValue as? SizedIterable<Child> ?: LazySizedCollection(SizedCollection(cachedValue as Child))
+            }
             cache -> {
                 transaction.entityCache.getOrPutReferrers(thisRef.id, reference, query).also {
                     thisRef.storeReferenceInCache(reference, it)

diff --git a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/h2/EntityReferenceCacheTest.kt b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/h2/EntityReferenceCacheTest.kt
@@ -95,7 +95,7 @@ class EntityReferenceCacheTest : DatabaseTestsBase() {
     }
 
     @Test
-    fun `test backReferencedOn works out of transaction via warmup`() {
+    fun `test backReferencedOn & optionalBackReferencedOn work out of transaction via load`() {
         var y1: EntityTestsData.YEntity by Delegates.notNull()
         var b1: EntityTestsData.BEntity by Delegates.notNull()
         executeOnH2(EntityTestsData.XTable, EntityTestsData.YTable) {
@@ -106,14 +106,16 @@ class EntityReferenceCacheTest : DatabaseTestsBase() {
                 }
             }
             assertFails { y1.b }
+            assertFails { y1.bOpt }
 
             transaction(dbWithCache) {
                 y1.refresh()
                 b1.refresh()
-                y1.load(EntityTestsData.YEntity::b)
+                y1.load(EntityTestsData.YEntity::b, EntityTestsData.YEntity::bOpt)
             }
 
             assertEquals(b1.id, y1.b?.id)
+            assertEquals(b1.id, y1.bOpt?.id)
         }
     }
 

diff --git a/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/entities/EntityTests.kt b/exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/entities/EntityTests.kt
@@ -88,6 +88,7 @@ object EntityTestsData {
     class YEntity(id: EntityID<String>) : Entity<String>(id) {
         var x by YTable.x
         val b: BEntity? by BEntity.backReferencedOn(XTable.y1)
+        val bOpt by BEntity optionalBackReferencedOn XTable.y1
 
         companion object : EntityClass<String, YEntity>(YTable)
     }