Undesirable runtime errors when creating custom types for Array

[mdedetrich]

When creating custom types for pg-array's type, its possible to get runtime cast errors (i.e. the code compiles fine)

As an example (and we had this happen to us), you can define a List[BigDecimal] mapping like this

implicit val bigDecimalTypeWrapper = new SimpleArrayJdbcType[BigDecimal]("numeric").to(_.toList)

You get a class cast exception at runtime (unable to cast a java.math.BigDecimal to a scala.mathBigDecimal). The following version is what you need to do

implicit val bigDecimalTypeWrapper = new SimpleArrayJdbcType[scala.math.BigDecimal]("numeric")
  .basedOn[java.math.BigDecimal]({ scalaBigDecimal: scala.math.BigDecimal => scalaBigDecimal.bigDecimal }, 
   javaBigDecimal => scala.math.BigDecimal(javaBigDecimal)).to(_.toList)

Both versions compile fine. The former should throw a compile time error (or work as desired)

[tminglei]

Yes, we should enhance it.

[tminglei]

Hi @mdedetrich, I added type checking logic, but it only takes effect when running instead of compiling.

If you have a better idea, pls don't hesitate to tell me.

[mdedetrich]

@tminglei I will have a better look as to why this is happening, is there a reason why this happens in slick-pg and not slick.

Maybe the only thing we need to do is to add implicit conversions from all of the Java JDBC types, which is another solution to the problem

[tminglei]

@mdedetrich, you mean, define another conversion interface, and make implementations for every supported Java JDBC types?

[mdedetrich]

@tminglei Yes. So we would create default conversions for all of the JDBC types (i.e. java.math.BigDecimal to scala.math.BigDecimal, java.lang.Long to scala.Long). Any custom types should fall outside of that

[tminglei]

Ok, I'll try on it.

[tminglei]

@mdedetrich enhanced. Can you help check it again?

Thanks!

[mdedetrich]

@tminglei Looking at it now

[mdedetrich]

@tminglei All good, seems to be working fine now with zero problems!