SHIMRR
A type-safe read-repair library (for scala)
At a glance...
sealed trait Version
case class NoFields() extends Version
case class Str1(stringField1: String) extends Version
case class Str1Str2(stringField1: String, stringField2: String) extends Version
case class Str1Str2Int1(stringField1: String, stringField2: String, intField1: Int) extends Version
"Given a valid pipeline" - {
@pipeline
val pipeline = new PipelineDsl4[NoFields, Str1, Str1Str2, Str1Str2Int1] {
from[NoFields] {
'stringField1 -> "str1"
}
from[Str1] {
'stringField2 -> (() => "str2")
}
from[Str1Str2] {
'intField1 -> ((_: Str1Str2) => 25)
}
from[Str1Str2Int1] {}
}
import pipeline.exports._
import syntax._
"all migrations should default correctly" in {
GeneratorDrivenPropertyChecks.forAll((in: Version) => {
val out = in.migrateTo[Str1Str2Int1]
in match {
case _: NoFields => out shouldBe Str1Str2Int1("str1", "str2", 25)
case x: Str1 => out shouldBe Str1Str2Int1(x.stringField1, "str2", 25)
case x: Str1Str2 => out shouldBe Str1Str2Int1(x.stringField1, x.stringField2, 25)
case x: Str1Str2Int1 => out shouldBe Str1Str2Int1(x.stringField1, x.stringField2, x.intField1)
}
})
}
}
Overview
- Migrate/ Upgrade Coproducts/ Products
- Compile time failure for any incomplete migrations
- Automatically drop remove fields
- Automatically re-order fields
- Default new fields using a simple, type-safe rules dsl
- Migrate collections of CoProducts/ Products (or anything for which a cats.Functor can be summoned)
Why was this library created
- Maintaining a stack of read-repair shims is hard work and becomes increasingly complex over time
- The version mapping code is largely boiler-plate and is dull to work with
Disclaimer
The inspiration for this project (along with a reasonable amount of the initial code) was taken from the excellent book
The type astronaut's guide to shapeless
Getting started
- Add the shimrr core and shimrr macros projects as dependencies
- Include the macro paradise compiler plugin
val shimrrDependencies: Seq[ModuleID] =Seq(
"uk.camsw" %% "shimrr-core" % "1.0.0",
"uk.camsw" %% "shimrr-macros" % "1.0.0"
)
lazy val metaMacroSettings: Seq[Def.Setting[_]] = Seq(
addCompilerPlugin("org.scalameta" % "paradise" % "3.0.0-M10" cross CrossVersion.full),
scalacOptions += "-Xplugin-require:macroparadise",
scalacOptions in(Compile, console) := Seq()
)
lazy val myProject = project
.settings(metaMacroSettings)
.settings(libraryDependencies ++= shimrrDependencies)
The tutorial
The tutorial is a WIP and is being used to drive future development of the library. Visit it regularly to find the latest enhancements
How to build and test
sbt clean update testThe backlog
Is currently held in trello, but feel free to create issues on github as I'll migrate soon
