Enhancement/2024 12 make encoder and decoder compatible with twiddles

[takapi327]

Implementation Details

Modification of Encoder and Decoder into a composable form using twiddles.

The method of building custom-type Decoders has changed. With this modification, Decoder can be converted to any type using the map function.

- given Decoder.Elem[Continent] = Decoder.Elem.mapping[String, Continent](str => Continent.valueOf(str.replace(" ", "_")))
+ given Decoder[Continent] = Decoder[String].map(str => Continent.valueOf(str.replace(" ", "_")))

Decoder is still constructed implicitly.

case class City(id: Int, name: String, age: Int)


sql"SELECT id, name, age FROM city LIMIT 1"
  .query[City]
  .to[Option]
  .readOnly(conn)

However, implicit searches may fail if there are many properties in the model.

[error]    |Implicit search problem too large.
[error]    |an implicit search was terminated with failure after trying 100000 expressions.
[error]    |The root candidate for the search was:
[error]    |
[error]    |  given instance given_Decoder_P in object Decoder  for  ldbc.dsl.codec.Decoder[City]}

In such cases, raising the search limit in the compilation options may resolve the problem.

scalacOptions += "-Ximplicit-search-limit:100000"

However, it may lead to amplification of compilation time. In that case, it can also be resolved by manually building the Decoder as follows.

given Decoder[City] = (Decoder[Int] *: Decoder[String] *: Decoder[Int]).to[City]

This is true not only for Decoder but also for Encoder.

Pull Request Checklist

• Wrote unit and integration tests
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code formatting by scalafmt (sbt scalafmtAll command execution)
• Add copyright headers to new files

References