How can I add a new type

[marcvk]

Hi,

I'm working on an older code base that uses java.util.Date (I know, I should switch to java.time), and I'm running into the problem that there is no implicit value for "Queryable.Row[Expr[Date], Date]".

As far as I can determine this occurs because java.util.Date is not directly supported by scalasql.

Is there a way to add support for java.util.Date.

Thanks,
Marc.

[lihaoyi]

@marcvk this looks like a job for a custom type mapper

• https://github.com/com-lihaoyi/scalasql/blob/main/docs/tutorial.md#custom-type-mappings

You'll have to experiment a bit to see what exactly your JDBC driver passes to ScalaSQL, but hopefully the implementation should be similar to to that for LocalDate

scalasql/scalasql/src/dialects/Dialect.scala

Lines 110 to 115 in d87f581

	implicit def LocalDateType: TypeMapper[LocalDate] = new LocalDateType
	class LocalDateType extends TypeMapper[LocalDate] {
	def jdbcType = JDBCType.DATE
	def get(r: ResultSet, idx: Int) = r.getObject(idx, classOf[LocalDate])
	def put(r: PreparedStatement, idx: Int, v: LocalDate) = r.setObject(idx, v)
	}

[marcvk]

The weird thing is, I tried recompiling scalasql with the implicits added directly to Dialects.scala, TypeMapper.scala and DialectTypeMappers.scala. See diff below, this is against HEAD as of today, and I got the exact same error:

diff --git a/scalasql/core/src/DialectTypeMappers.scala b/scalasql/core/src/DialectTypeMappers.scala
index f7924b0..3e4783f 100644
--- a/scalasql/core/src/DialectTypeMappers.scala
+++ b/scalasql/core/src/DialectTypeMappers.scala
@@ -28,6 +28,7 @@ trait DialectTypeMappers extends DialectConfig {
   implicit def BooleanType: TypeMapper[Boolean]
   implicit def UuidType: TypeMapper[UUID]
   implicit def BytesType: TypeMapper[geny.Bytes]
+  implicit def UtilDateType: TypeMapper[java.util.Date]
   implicit def LocalDateType: TypeMapper[LocalDate]
   implicit def LocalTimeType: TypeMapper[LocalTime]
 
diff --git a/scalasql/core/src/TypeMapper.scala b/scalasql/core/src/TypeMapper.scala
index e212467..0978d1e 100644
--- a/scalasql/core/src/TypeMapper.scala
+++ b/scalasql/core/src/TypeMapper.scala
@@ -87,6 +87,9 @@ object TypeMapper {
     d.UuidType
   implicit def bytesFromDialectTypeMappers(implicit d: DialectTypeMappers): TypeMapper[geny.Bytes] =
     d.BytesType
+  implicit def utilDateFromDialectTypeMappers(
+      implicit d: DialectTypeMappers
+  ): TypeMapper[java.util.Date] = d.UtilDateType
   implicit def localDateFromDialectTypeMappers(
       implicit d: DialectTypeMappers
   ): TypeMapper[LocalDate] = d.LocalDateType
diff --git a/scalasql/src/dialects/Dialect.scala b/scalasql/src/dialects/Dialect.scala
index c79b016..f5244ab 100644
--- a/scalasql/src/dialects/Dialect.scala
+++ b/scalasql/src/dialects/Dialect.scala
@@ -107,6 +107,13 @@ trait Dialect extends DialectTypeMappers {
     def put(r: PreparedStatement, idx: Int, v: geny.Bytes) = r.setBytes(idx, v.array)
   }
 
+  implicit def UtilDateType: TypeMapper[java.util.Date] = new UtilDateType
+  class UtilDateType extends TypeMapper[java.util.Date] {
+    def jdbcType = JDBCType.TIMESTAMP
+    def get(r: ResultSet, idx: Int) = new java.util.Date(r.getDate(idx).getTime)
+    def put(r: PreparedStatement, idx: Int, v: java.util.Date) = r.setDate(idx, new java.sql.Date(v.getTime))
+  }
+
   implicit def LocalDateType: TypeMapper[LocalDate] = new LocalDateType
   class LocalDateType extends TypeMapper[LocalDate] {
     def jdbcType = JDBCType.DATE

[lihaoyi]

There has to be something weird with implicit resolution in Scala 2.13.x. When I put println(implicitly[scalasql.Queryable.Row[scalasql.core.Expr[java.util.Date],java.util.Date]]) in the object Main extends App, it compiles and prints the resolved implicit successfully. But somehow it can't find the exact same implicit when resolving it as part of the extends Table constructor.

[marcvk]

@lihaoyi I've converted my app to scala 3.4.2, which went reasonably well, but then I struggled a long time getting it to work because of forgetting to import DateUtil._ at the locations where I am using TimeInterval queries.

Is there a more generic way to make this more foolproof, because you get no usable error feedback (not to me in any case) that you forgot to import the implicits. It actually gave me different kinds of errors in different test programs I used.

[lihaoyi]

@marcvk this wont work in the general case, but for something as fundamental as java.util.Date we could add it to scalasql's own codebase so it gets picked up automatically together with the other builtin implicits. If you have some time send a PR and ill review/merge it

[marcvk]

I've just submitted a PR (#24). I've added tests and the tests pass. Let me know if anything else is needed.