fix(model-datastructure): tree serialization wasn't backwards compatible

It caused a MismatchingObjectKeyAndValueException when an existing model was loaded and then pushed.

Author: slisson

model-datastructure/src/commonMain/kotlin/org/modelix/model/persistent/CPTree.kt

@@ -68,7 +68,7 @@ data class CPTree(
             usesRoleIds -> INT64_WITH_ROLE_IDS
             else -> INT64_WITH_ROLE_NAMES
         }
-        return "$id/$pv/${getTreeReference().getHash()}/${if (usesRoleIds) "i" else "n"}"
+        return "$id/$pv/${getTreeReference().getHash()}${if (usesRoleIds) "/i" else ""}"
     }
 
     override fun getDeserializer(): IObjectDeserializer<CPTree> = DESERIALIZER
@@ -133,7 +133,12 @@ data class CPTree(
             val graph = referenceFactory as IObjectGraph
             return when (persistenceVersion) {
                 STRING_IDS -> {
-                    val usesRoleIds = parts.getOrNull(3) != "n"
+                    val usesRoleIds = when (val part = parts.getOrNull(3)) {
+                        null -> false
+                        "n" -> false
+                        "i" -> true
+                        else -> throw IllegalArgumentException("Unknown value `$part` in $input")
+                    }
                     CPTree(
                         id = treeId,
                         int64Hamt = null,

model-datastructure/src/commonTest/kotlin/TreeSerializationTest.kt

@@ -1,3 +1,4 @@
+import org.modelix.datastructures.objects.IObjectGraph
 import org.modelix.model.IKeyValueStore
 import org.modelix.model.api.IBranch
 import org.modelix.model.api.IConcept
@@ -11,6 +12,7 @@ import org.modelix.model.lazy.CLVersion
 import org.modelix.model.lazy.createObjectStoreCache
 import org.modelix.model.operations.LegacyBranchAsMutableModelTree
 import org.modelix.model.operations.OTBranch
+import org.modelix.model.persistent.CPTree
 import org.modelix.model.persistent.MapBaseStore
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -314,6 +316,13 @@ class TreeSerializationTest {
         assertStore(mapStore)
     }
 
+    @Test
+    fun backwards_compatibility_of_persistence_version_2() {
+        val serialized = "4f7aa052-43e0-4f5e-b5c8-f197a80507a0/2/V_4I6*Hbk19Lb1sBNIU1k7aA9kGXTI3zBQqYZ9CZje74"
+        val deserialized = CPTree.deserialize(serialized, IObjectGraph.FREE_FLOATING)
+        assertEquals(serialized, deserialized.serialize())
+    }
+
     fun assertStore(store: IKeyValueStore) {
         val deserializedVersion = CLVersion.loadFromHash(store["branch_master"]!!, createObjectStoreCache(store))
         val deserializedTree = deserializedVersion.tree