Add UpdateBuilder#setNull(T) to simplify usages like "it[column] = nu…

…ll as Int?"

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/statements/UpdateBuilder.kt

@@ -37,6 +37,13 @@ abstract class UpdateBuilder<out T>(type: StatementType, targets: List<Table>) :
         values[column] = value
     }
 
+    /**
+     * Sets column value to null.
+     * This method is helpful for "optional references" since compiler can't decide between
+     * "null as T?" and "null as EntityID<T>?".
+     */
+    fun <T> setNull(column: Column<T?>) = set(column, null as T?)
+
     open operator fun <S> set(column: Column<S>, value: Expression<out S>) = update(column, value)
 
     open operator fun <S> set(column: CompositeColumn<S>, value: S) {

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/dml/InsertTests.kt

@@ -265,6 +265,10 @@ class InsertTests : DatabaseTestsBase() {
             tbl.verifyInsert(null) {
                 it[nullableInt] = LiteralOp(nullableInt.columnType, null)
             }
+
+            tbl.verifyInsert(null) {
+                it.setNull(nullableInt)
+            }
         }
     }
 

exposed-tests/src/test/kotlin/org/jetbrains/exposed/sql/tests/shared/entities/EntityTests.kt

@@ -225,6 +225,9 @@ class EntityTests : DatabaseTestsBase() {
                 // it[EntityTestsData.XTable.y1] = null
                 it[y1] = null as EntityID<String>?
             }
+            EntityTestsData.XTable.insert {
+                it.setNull(y1)
+            }
         }
     }