1

Update: see answers below for solution to this problem. There's a second problem (macro now can't find Pojo), question about second problem here: Scala macro can't find my java class

I'm creating a scala macro to automatically generate case classes from POJOs (in order to make working with avro a little bit nicer).

Everything "works" except that the compiler chokes on built-in java classes like java.util.List, and java.lang.Object.

My question is: how do I generate code in the macro such that the compiler resolves java classes?

Example error message:

(without // coments in Pojo.java)

[info] Compiling 1 Scala source to /Users/marcin/development/repo/problemdemo/target/scala-2.11/classes...
fieldType:java.util.List
fieldType:Int
fieldType:java.util.List
Expr[Any](case class Demo extends scala.Product with scala.Serializable {
  <caseaccessor> <paramaccessor> val baz: java.util.List[com.squarefoot.Pojo] = _;
  <caseaccessor> <paramaccessor> val bar: Int = _;
  <caseaccessor> <paramaccessor> val foo: java.util.List[java.lang.Integer] = _;
  def <init>(baz: java.util.List[com.squarefoot.Pojo], bar: Int, foo: java.util.List[java.lang.Integer]) = {
    super.<init>();
    ()
  }
})
[error] /Users/marcin/development/repos/problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:5: not found: type java.util.List
[error] @Caseify(classOf[com.squarefoot.Pojo])
[error]  ^
[error] one error found
[error] (root/compile:compileIncremental) Compilation failed
[error] Total time: 17 s, completed Dec 11, 2016 12:00:57 PM

(Pojo.java as shown)

[info] Compiling 1 Scala source to /Users/marcin/development/repos/problemdemo/target/scala-2.11/classes...
fieldType:java.lang.Object
fieldType:Int
Expr[Any](case class Demo extends scala.Product with scala.Serializable {
  <caseaccessor> <paramaccessor> val qux: java.lang.Object = _;
  <caseaccessor> <paramaccessor> val bar: Int = _;
  def <init>(qux: java.lang.Object, bar: Int) = {
    super.<init>();
    ()
  }
})
[error] /Users/marcin/development/repos/problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:5: not found: type java.lang.Object
[error] @Caseify(classOf[com.squarefoot.Pojo])
[error]  ^
[error] one error found
[error] (root/compile:compileIncremental) Compilation failed
[error] Total time: 6 s, completed Dec 11, 2016 12:04:29 PM

Edit: Results of showRaw

showRaw gives output like this, which looks fine to me:

ValDef(Modifiers(DEFERRED), TermName("availablebuildouts"), AppliedTypeTree(Ident(TypeName("java.util.List")), List(Ident(TypeName("com.squarefoot.buildouttype")))), EmptyTree)

problemdemo/avroschemas/src/main/java/com/squarefoot/Pojo.java:

package com.squarefoot;

public class Pojo {
    //public java.util.List<Integer> foo;
    public int bar;
    //public java.util.List<Pojo> baz;
    public java.lang.Object qux;
}

problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:

package com.squarefoot.converters

import com.squarefoot.Pojo

class Foomin {
  val foobar: java.util.List[Int]
}
    
@Caseify(classOf[com.squarefoot.Pojo])
case class Demo()

problemdemo/macros/src/main/scala/com/squarefoot/converters/Caseify.scala:

package com.squarefoot.converters

import scala.language.experimental.macros
import scala.annotation.StaticAnnotation
import scala.reflect.macros.Context

/** 
  *  Generate case class from POJO
  *  ex:
  *  @Caseify(classOf[com.squarefoot.incominglisting])
  *  case class Incominglisting()

  * NOTE that the type parameter to classOf must be provided as a fully
  * qualified name, otherwise the macro code here won't be able to find it.
  * 
  * Generates a case class with the same members as the public, non-static
  * members of the pojo
  * 
  * Note that you must have all types used in the POJO in scope where the macro
  * is invoked
  */

class Caseify[T](source: Class[T]) extends StaticAnnotation {
  def macroTransform(annottees: Any*) = macro CaseifyMacro.expand_impl[T]
}

object CaseifyMacro {
  /** generate case class from POJO */
  def expand_impl[T](c: Context)(annottees: c.Expr[Any]*) = {
    import c.universe._

    // macro expand the macro expression itself to extract param
    val source: Class[T] = c.prefix.tree match {
      case q"new Caseify($param)" => c.eval[Class[T]](c.Expr(param))
    }

    val rm = scala.reflect.runtime.currentMirror
    val vars =
      rm.classSymbol(source).toType.members.map(_.asTerm).
        filter(_.isVar).filter(_.isPublic)

    lazy val fields = vars.map({f=>
      val fieldName = TermName(f.name.toString)
      val fieldType = TypeName(f.typeSignature.typeConstructor.toString)
      val typeArgs = f.typeSignature.typeArgs.map(a=>TypeName(a.toString))
      println("fieldType:"+fieldType.toString)
      q"val $fieldName: $fieldType"
      if(typeArgs.size > 0)
        q"val $fieldName: $fieldType[..$typeArgs]"
      else
         q"val $fieldName: $fieldType"
    })

    annottees.map(_.tree) match {
      case List(q"case class $newname()") => {
        val q = c.Expr[Any](
        // Add your own logic here, possibly using arguments on the annotation.
          q"""
          case class $newname(..$fields)
        """)
        println(q.toString)
        q
      }
      // Add validation and error handling here.
    }
  }
}

Sbt files:

problemdemo/build.sbt

name := "data-importer"


addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)

scalaVersion := "2.11.8"
val avroVersion = "1.8.1"

lazy val root =
        project.in( file(".") )
          .aggregate(avroschemas, macros).dependsOn(macros, avroschemas)

lazy val macros = project.dependsOn(avroschemas)

lazy val avroschemas = project



libraryDependencies ++= Seq(
  "org.scala-lang" % "scala-reflect" % scalaVersion.value
)


// better error reporting
scalacOptions in Test ++= Seq("-Yrangepos")

run in Compile := Defaults.runTask(fullClasspath in Compile, mainClass in (Compile, run), runner in (Compile, run))

problemdemo/macros/build.sbt

name := "data-importer-macros"


addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)

organization := "com.squarefoot"
scalaVersion := "2.11.3"



libraryDependencies ++= Seq(
  "org.scala-lang" % "scala-reflect" % scalaVersion.value
)

scalacOptions in Test ++= Seq("-Yrangepos")

problemdemo/avroschemas/build.sbt

name := "data-importer-avroschemas"

addCompilerPlugin("org.scalamacros" % "paradise" % "2.1.0" cross CrossVersion.full)

organization := "com.squarefoot"
scalaVersion := "2.11.8"


// better error reporting
scalacOptions in Test ++= Seq("-Yrangepos")

run in Compile := Defaults.runTask(fullClasspath in Compile, mainClass in (Compile, run), runner in (Compile, run))
Community
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Marcin
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2 Answers2

1

Basically, instead of TypeName("java.util.List"), you want something like (based on the example in http://docs.scala-lang.org/overviews/reflection/symbols-trees-types.html#tree-creation-via-reify, can't test at the moment) Select(Select(This(TypeName("java")), TypeName("util")), TypeName("List")). If you do showRaw on your input tree, you should see more precisely. So instead of TypeName(...toString), split on .. Maybe just removing TypeName:

val fieldType = f.typeSignature.typeConstructor
val typeArgs = f.typeSignature.typeArgs

will be enough?

Alexey Romanov
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  • Thank you very much for this. I've now been able to test this out. The snippet you give *should* work, because the types look identical to those produced by `TypeName`, but for some reason the compiler complains about lifting them. Using `tq""` has - I believe - generated the structure you suggest. I'm going to post what I have as another answer. Unfortunately, the macro isn't working because of another related problem (details will follow in the answer and I'll edit the question to refer to the additional question). – Marcin Dec 23 '16 at 15:23
1

So, I don't yet have a working macro, but I have solved this problem with the help of Alexey Romanov's answer. This code results in the error:

[error] /Users/marcin/development/repos/problemdemo/src/main/scala/com/squarefoot/converters/problemdemo.scala:10: not found: type com.squarefoot.Pojo
[error] @Caseify(classOf[com.squarefoot.Pojo])

I'm about to open a separate question about that issue. 

package com.squarefoot.converters

import scala.language.experimental.macros
import scala.annotation.StaticAnnotation
import scala.reflect.macros.Context

/** 
  *  Generate case class from POJO
  *  ex:
  *  @Caseify(classOf[com.squarefoot.incominglisting])
  *  case class Incominglisting()

  * NOTE that the type parameter to classOf must be provided as a fully
  * qualified name, otherwise the macro code here won't be able to find it.
  * 
  * Generates a case class with the same members as the public, non-static
  * members of the pojo
  * 
  * Note that you must have all types used in the POJO in scope where the macro
  * is invoked
  */

class Caseify[T](source: Class[T]) extends StaticAnnotation {
  def macroTransform(annottees: Any*) = macro CaseifyMacro.expand_impl[T]
}

object CaseifyMacro {
  /** generate case class from POJO */
  def expand_impl[T](c: Context)(annottees: c.Expr[Any]*) = {
    import c.universe._

    // macro expand the macro expression itself to extract param
    val source: Class[T] = c.prefix.tree match {
      case q"new Caseify($param)" => c.eval[Class[T]](c.Expr(param))
    }

    val rm = scala.reflect.runtime.currentMirror


    val vars =
      rm.classSymbol(source).toType.members.map(_.asTerm).
        filter(_.isVar).filter(_.isPublic)

    val fields = vars.map({f=>
      val fieldName = TermName(f.name.toString)

      val fieldType = tq"${f.typeSignature.typeConstructor.typeSymbol.fullName}"
      val rawTypeArgs = f.typeSignature.typeArgs.map(a=>TypeName(a.toString))
      val typeArgs = tq"${rawTypeArgs}"
      println("typeArgs: "+typeArgs.toString)
      println("fieldType:"+fieldType.getClass.toString+"|"+fieldType.toString)
      println(f.typeSignature.typeSymbol.asType.name.getClass.toString)
      val arraylistname = tq"java.util.ArrayList"
      println("DEBUG:"+tq"${arraylistname}".toString+"|"+f.typeSignature.typeConstructor.typeSymbol.fullName)
      q"val $fieldName: $fieldType"
      if(rawTypeArgs.nonEmpty) {
        val appliedFieldType = tq"${arraylistname}[..$rawTypeArgs]"
        q"val $fieldName: $appliedFieldType"
      }
      else
         q"val $fieldName: $fieldType"
    })

    annottees.map(_.tree) match {
      case List(q"case class $newname()") => {
        val q = c.Expr[Any](
        // Add your own logic here, possibly using arguments on the annotation.
          q"""
          case class $newname(..$fields)
        """)
        println(q.toString)
        q
      }
      // Add validation and error handling here.
    }
  }
}
Marcin
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