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reflection still very non-deterministic #6573

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scabug opened this issue Oct 27, 2012 · 5 comments
Open

reflection still very non-deterministic #6573

scabug opened this issue Oct 27, 2012 · 5 comments
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@scabug
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@scabug scabug commented Oct 27, 2012

scala> import scala.reflect.runtime.universe._
import scala.reflect.runtime.universe._

scala> rootMirror.staticPackage("java.lang").typeSignature.members.size
res0: Int = 16

scala> rootMirror.staticPackage("java.lang").typeSignature.members.flatMap(_.typeSignature.members)
res1: Iterable[reflect.runtime.universe.Symbol] = List(value serialVersionUID, constructor StringBuilder, ....)

scala> rootMirror.staticPackage("java.lang").typeSignature.members.size
res2: Int = 31
@scabug
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@scabug scabug commented Oct 27, 2012

Imported From: https://issues.scala-lang.org/browse/SI-6573?orig=1
Reporter: @paulp
Affected Versions: 2.10.0-RC1, 2.11.0-M1

@scabug
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@scabug scabug commented Oct 28, 2012

@xeno-by said (edited on Oct 28, 2012 5:36:51 AM UTC):
Reflection uses classloaders, therefore it cannot exhaustively enumerate members of packages. Any ideas how to defeat that?

@scabug
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@scabug scabug commented Oct 28, 2012

@retronym said:
While it can't enumerate members of packages in general, it can be done if you make some assumptions about the classloader (See, for example, Spring's PathMatchingResourcePatternResolver.)

I don't suggest to offer that functionality out of the box (maintaining and supporting that sort of code is expensive), but you might offer a hook at the point of mirror creation where the caller could provide a package enumerator.

@scabug
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@scabug scabug commented Apr 29, 2013

@clhodapp said:
Also see Reflections, which is more focused on finding classes.

@scabug
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@scabug scabug commented Apr 29, 2013

@clhodapp said (edited on Apr 29, 2013 3:42:50 AM UTC):
It's worse than you claim: simply being loaded is not enough to make a class show up:

package foo

import reflect.runtime.universe._
import reflect.runtime.{currentMirror=>cm}

class C

object Main extends App {

	val pkg = cm.staticPackage("foo")
	println(pkg.moduleClass.typeSignature.members)

	pkg.moduleClass.typeSignature.member(newTypeName("Main"))
	println(pkg.moduleClass.typeSignature.members)

	cm.classLoader.loadClass("foo.C")
	println(pkg.moduleClass.typeSignature.members)

	pkg.moduleClass.typeSignature.member(newTypeName("C"))
	println(pkg.moduleClass.typeSignature.members)

}
[info] Running foo.Main
Scope{

}
Scope{
  object Main;
  class Main extends
}
Scope{
  object Main;
  class Main extends
}
Scope{
  object C;
  class C extends ;
  object Main;
  class Main extends
}
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