Fix UnexpectedNullValueInColumn exception in caseClassParser if first…

… parameter in case class is optional (#98)

Co-authored-by: Aleksandr Shabalin <[email protected]>

src/it/scala/com/ringcentral/cassandra4io/cql/CqlSuite.scala

@@ -399,6 +399,13 @@ trait CqlSuite {
     } yield expect(row.isDefined && row.get.data.isEmpty)
   }
 
+  test("decoding from null should return None for optional case class first parameter") { session =>
+    case class OptDataReverse(data: Option[String], id: Long)
+    for {
+      row <- cql"select data, id FROM cassandra4io.test_data WHERE id = 0".as[OptDataReverse].selectFirst(session)
+    } yield expect(row.isDefined && row.get.data.isEmpty)
+  }
+
   test("decoding from null should raise error String field in case class") { session =>
     for {
       result <- cql"select id, data FROM cassandra4io.test_data WHERE id = 0".as[Data].selectFirst(session).attempt

src/main/scala/com/ringcentral/cassandra4io/cql/Reads.scala

@@ -121,8 +121,12 @@ trait ReadsLowestPriority {
   implicit def caseClassParser[A, R <: HList](implicit
     gen: Generic[A] { type Repr = R },
     reprParser: Reads[R]
-  ): Reads[A] = (row: Row, index: Int) => {
-    val rep = reprParser.read(row, index)
-    gen.from(rep)
-  }
+  ): Reads[A] =
+    new Reads[A] {
+      override def readNullable(row: Row, index: Int): A = {
+        val rep = reprParser.read(row, index)
+        gen.from(rep)
+      }
+      override def read(row: Row, index: Int): A = readNullable(row, index)
+    }
 }