fix!: EXPOSED-546 [H2] Column with Json default value can not be used as databaseGenerated

documentation-website/Writerside/topics/Breaking-Changes.md

@@ -24,6 +24,7 @@
   values are inserted.
 * The transformation of a nullable column (`Column<Unwrapped?>.transform()`) requires handling null values.
   This enables conversions from `null` to a non-nullable value, and vice versa.
+* In H2 the definition of json column with default value changed from `myColumn JSON DEFAULT '{"key": "value"}'` to `myColumn JSON DEFAULT JSON '{"key": "value"}'`
 
 ## 0.54.0
 

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

@@ -214,7 +214,10 @@ object SchemaUtils {
 
                                     is MariaDBDialect -> processed.trim('\'')
                                     is MysqlDialect -> "_utf8mb4\\'${processed.trim('(', ')', '\'')}\\'"
-                                    else -> processed.trim('\'')
+                                    else -> when {
+                                        processed.startsWith('\'') && processed.endsWith('\'') -> processed.trim('\'')
+                                        else -> processed
+                                    }
                                 }
                             }
 

exposed-core/src/main/kotlin/org/jetbrains/exposed/sql/vendors/DataTypeProvider.kt

@@ -141,12 +141,6 @@ abstract class DataTypeProvider {
 
     /** Returns the SQL representation of the specified expression, for it to be used as a column default value. */
     open fun processForDefaultValue(e: Expression<*>): String = when {
-        e is LiteralOp<*> && e.columnType is JsonColumnMarker -> if (currentDialect is H2Dialect) {
-            "$e".substringAfter("JSON ")
-        } else {
-            "'$e'"
-        }
-
         e is LiteralOp<*> -> (e.columnType as IColumnType<Any?>).valueAsDefaultString(e.value)
         e is Function<*> -> "$e"
         currentDialect is MysqlDialect -> "$e"

exposed-json/api/exposed-json.api

@@ -40,6 +40,7 @@ public class org/jetbrains/exposed/sql/json/JsonColumnType : org/jetbrains/expos
 	public final fun getDeserialize ()Lkotlin/jvm/functions/Function1;
 	public final fun getSerialize ()Lkotlin/jvm/functions/Function1;
 	public fun getUsesBinaryFormat ()Z
+	public fun nonNullValueAsDefaultString (Ljava/lang/Object;)Ljava/lang/String;
 	public fun nonNullValueToString (Ljava/lang/Object;)Ljava/lang/String;
 	public fun notNullValueToDB (Ljava/lang/Object;)Ljava/lang/Object;
 	public fun parameterMarker (Ljava/lang/Object;)Ljava/lang/String;

exposed-json/src/main/kotlin/org/jetbrains/exposed/sql/json/JsonColumnType.kt

@@ -71,6 +71,13 @@ open class JsonColumnType<T : Any>(
         }
         super.setParameter(stmt, index, parameterValue)
     }
+
+    override fun nonNullValueAsDefaultString(value: T): String {
+        return when {
+            currentDialect is H2Dialect -> "JSON '${notNullValueToDB(value)}'"
+            else -> "'${notNullValueToDB(value)}'"
+        }
+    }
 }
 
 /**

exposed-json/src/test/kotlin/org/jetbrains/exposed/sql/json/JsonColumnTests.kt

@@ -425,4 +425,26 @@ class JsonColumnTests : DatabaseTestsBase() {
             assertContentEquals(data, tester.selectAll().single()[tester.numbers])
         }
     }
+
+    @Test
+    fun testJsonAsDefault() {
+        val defaultUser = User("name", "team")
+        val tester = object : IntIdTable("testJsonAsDefault") {
+            val value = json<User>("value", Json.Default)
+                .default(defaultUser)
+        }
+
+        val testerDatabaseGenerated = object : IntIdTable("testJsonAsDefault") {
+            val value = json<User>("value", Json.Default)
+                .databaseGenerated()
+        }
+
+        // MySQL versions prior to 8.0.13 do not accept default values on JSON columns
+        withTables(excludeSettings = listOf(TestDB.MYSQL_V5), tester) {
+            testerDatabaseGenerated.insert { }
+
+            val value = testerDatabaseGenerated.selectAll().single()[tester.value]
+            assertEquals(defaultUser, value)
+        }
+    }
 }