Support checkpoints without bucket priorities

Author: simolus3

core/src/commonMain/kotlin/com/powersync/bucket/BucketChecksum.kt

@@ -6,7 +6,7 @@ import kotlinx.serialization.Serializable
 @Serializable
 internal data class BucketChecksum(
     val bucket: String,
-    val priority: BucketPriority,
+    val priority: BucketPriority = BucketPriority.DEFAULT_PRIORITY,
     val checksum: Int,
     val count: Int? = null,
     @SerialName("last_op_id") val lastOpId: String? = null,

core/src/commonMain/kotlin/com/powersync/bucket/BucketPriority.kt

@@ -16,5 +16,11 @@ public value class BucketPriority(private val priorityCode: Int): Comparable<Buc
 
     public companion object {
         internal val FULL_SYNC_PRIORITY: BucketPriority = BucketPriority(Int.MAX_VALUE)
+
+        /**
+         * The assumed priority for buckets when talking to older sync service instances that don't
+         * support bucket priorities.
+         */
+        internal val DEFAULT_PRIORITY: BucketPriority = BucketPriority(3)
     }
 }

core/src/commonTest/kotlin/com/powersync/sync/SyncLineTest.kt

@@ -1,5 +1,6 @@
 package com.powersync.sync
 
+import com.powersync.bucket.BucketChecksum
 import com.powersync.bucket.BucketPriority
 import com.powersync.bucket.Checkpoint
 import com.powersync.utils.JsonUtil
@@ -19,6 +20,22 @@ class SyncLineTest {
         )), """{"checkpoint": {"last_op_id": "10", "buckets": []}}""")
     }
 
+    @Test
+    fun testDeserializeCheckpointNoPriority() {
+        checkDeserializing(SyncLine.FullCheckpoint(Checkpoint(
+            lastOpId = "10",
+            checksums = listOf(BucketChecksum(bucket = "a", priority = BucketPriority(3), checksum = 10)),
+        )), """{"checkpoint": {"last_op_id": "10", "buckets": [{"bucket": "a", "checksum": 10}]}}""")
+    }
+
+    @Test
+    fun testDeserializeCheckpointWithPriority() {
+        checkDeserializing(SyncLine.FullCheckpoint(Checkpoint(
+            lastOpId = "10",
+            checksums = listOf(BucketChecksum(bucket = "a", priority = BucketPriority(1), checksum = 10)),
+        )), """{"checkpoint": {"last_op_id": "10", "buckets": [{"bucket": "a", "priority": 1, "checksum": 10}]}}""")
+    }
+
     @Test
     fun testDeserializeCheckpointDiff() {
         checkDeserializing(SyncLine.CheckpointDiff(