fix null enum bug

Author: vincentlauvlwj

ktorm-core/src/main/kotlin/org/ktorm/schema/SqlTypes.kt

@@ -501,12 +501,24 @@ public inline fun <reified C : Enum<C>> BaseTable<*>.enum(name: String): Column<
  *
  * @property enumClass the enum class.
  */
-public class EnumSqlType<C : Enum<C>>(public val enumClass: Class<C>) : SqlType<C>(Types.VARCHAR, "enum") {
+public class EnumSqlType<C : Enum<C>>(public val enumClass: Class<C>) : SqlType<C>(Types.OTHER, "enum") {
 
     private val hasPostgresqlDriver by lazy {
         runCatching { Class.forName("org.postgresql.Driver") }.isSuccess
     }
 
+    override fun setParameter(ps: PreparedStatement, index: Int, parameter: C?) {
+        if (parameter != null) {
+            doSetParameter(ps, index, parameter)
+        } else {
+            if (hasPostgresqlDriver && ps is PGStatement) {
+                ps.setNull(index, Types.OTHER)
+            } else {
+                ps.setNull(index, Types.VARCHAR)
+            }
+        }
+    }
+
     override fun doSetParameter(ps: PreparedStatement, index: Int, parameter: C) {
         if (hasPostgresqlDriver && ps is PGStatement) {
             ps.setObject(index, parameter.name, Types.OTHER)

ktorm-support-mysql/src/test/kotlin/org/ktorm/support/mysql/MySqlTest.kt

@@ -1,7 +1,7 @@
 package org.ktorm.support.mysql
 
-import org.hamcrest.CoreMatchers
-import org.hamcrest.MatcherAssert
+import org.hamcrest.CoreMatchers.equalTo
+import org.hamcrest.MatcherAssert.assertThat
 import org.junit.ClassRule
 import org.junit.Test
 import org.ktorm.BaseTest
@@ -524,12 +524,16 @@ class MySqlTest : BaseTest() {
         }
 
         val count = database.sequenceOf(TableWithEnum).count { it.current_mood eq Mood.SAD }
+        assertThat(count, equalTo(1))
 
-        MatcherAssert.assertThat(count, CoreMatchers.equalTo(1))
+        val mood = database.sequenceOf(TableWithEnum).filter { it.id eq 1 }.mapColumns { it.current_mood }.first()
+        assertThat(mood, equalTo(Mood.SAD))
 
-        val currentMood =
-            database.sequenceOf(TableWithEnum).filter { it.id eq 1 }.mapColumns { it.current_mood }.first()
+        database.insert(TableWithEnum) {
+            set(it.current_mood, null)
+        }
 
-        MatcherAssert.assertThat(currentMood, CoreMatchers.equalTo(Mood.SAD))
+        val mood1 = database.sequenceOf(TableWithEnum).filter { it.id eq 2 }.mapColumns { it.current_mood }.first()
+        assertThat(mood1, equalTo(null))
     }
 }

ktorm-support-postgresql/src/test/kotlin/org/ktorm/support/postgresql/PostgreSqlTest.kt

@@ -783,13 +783,17 @@ class PostgreSqlTest : BaseTest() {
         }
 
         val count = database.sequenceOf(TableWithEnum).count { it.current_mood eq Mood.SAD }
-
         assertThat(count, equalTo(1))
 
-        val currentMood =
-            database.sequenceOf(TableWithEnum).filter { it.id eq 1 }.mapColumns { it.current_mood }.first()
+        val mood = database.sequenceOf(TableWithEnum).filter { it.id eq 1 }.mapColumns { it.current_mood }.first()
+        assertThat(mood, equalTo(Mood.HAPPY))
+
+        database.insert(TableWithEnum) {
+            set(it.current_mood, null)
+        }
 
-        assertThat(currentMood, equalTo(Mood.HAPPY))
+        val mood1 = database.sequenceOf(TableWithEnum).filter { it.id eq 3 }.mapColumns { it.current_mood }.first()
+        assertThat(mood1, equalTo(null))
     }
 
     @Test