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// Copyright: 2017 - 2018 Sam Halliday
// License: http://www.gnu.org/licenses/lgpl-3.0.en.html
// To install: copy this file, changing the package. Canonical latest is
// https://gitlab.com/fommil/scalaz-deriving/tree/master/deriving-plugin
package scalaz.plugins.deriving
import scala.Predef.ArrowAssoc
import scala.deprecated
import scala.collection.immutable.Map
import scala.collection.breakOut
import scala.reflect.internal.util._
import scala.tools.nsc._
import scala.tools.nsc.plugins._
import scala.tools.nsc.transform._
/**
* A compiler plugin for code generation when an annotation is on a class, trait
* or object. For classes and traits, ensures that a companion is created and
* passes both to the implementation.
*
* TL;DR a drop-in replacement for syntactic annotation macros.
*
* The main advantage over annotation macros is that it works in all tooling
* (except IntelliJ) and this approach will work in the long term
* (macro-paradise is abandoned).
*
* The caveats are that typechecking and naming will not occur, so the code
* generation / rewrites must be purely syntactic. If you require any type
* inference, point your generated code at a blackbox macro that you implement
* downstream.
*
* Unlike macro annotations, the annotation is not removed. This avoids false
* negatives regarding unused imports. It should be possible to add a -cleanup
* phase to remove the trigger annotations if needed.
*/
abstract class AnnotationPlugin(override val global: Global) extends Plugin {
import global._
override lazy val description: String =
s"Generates code for annotations $triggers"
/** Annotations that trigger the plugin */
def triggers: List[String]
def updateClass(triggered: List[Tree], clazz: ClassDef): ClassDef
def updateCompanion(
triggered: List[Tree],
clazz: ClassDef,
companion: ModuleDef
): ModuleDef
def updateModule(triggered: List[Tree], module: ModuleDef): ModuleDef
/** Use to create code that shortcuts in ENSIME and ScalaIDE */
def isIde: Boolean = global.isInstanceOf[tools.nsc.interactive.Global]
def isScaladoc: Boolean = global.isInstanceOf[tools.nsc.doc.ScaladocGlobal]
// best way to inspect a tree, just call this
def debug(name: String, tree: Tree): Unit =
Predef.println(
s"====\n$name ${tree.id} ${tree.pos}:\n${showCode(tree)}\n${showRaw(tree)}"
)
// recovers the final part of an annotation
def annotationName(ann: Tree): TermName =
ann.children.collectFirst {
case Select(New(Ident(name)), _) => name.toTermName
case Select(New(Select(_, name)), _) => name.toTermName
}.getOrElse(abort(s"no name for $ann"))
// case classes without companions should inherit Function
def addSuperFunction(@deprecated("unused", "") clazz: ClassDef): Boolean =
true
implicit class RichTree[T <: Tree](private val t: T) {
/** when generating a tree, use this to generate positions all the way down. */
def withAllPos(pos: Position): T = {
t.foreach { p =>
val _ = p.setPos(
new TransparentPosition(pos.source, pos.start, pos.end, pos.end)
)
}
t
}
}
private def phase = new PluginComponent with TypingTransformers {
override val phaseName: String = AnnotationPlugin.this.name
override val global: AnnotationPlugin.this.global.type =
AnnotationPlugin.this.global
override final def newPhase(prev: Phase): Phase = new StdPhase(prev) {
override def apply(unit: CompilationUnit): Unit =
newTransformer(unit).transformUnit(unit)
}
override val runsAfter: List[String] = "parser" :: Nil
override val runsBefore: List[String] = "namer" :: Nil
private def newTransformer(unit: CompilationUnit) =
new TypingTransformer(unit) {
override def transform(tree: Tree): Tree =
autobots(super.transform(tree))
}
val Triggers: List[TypeName] = triggers.map(newTypeName)
private def hasTrigger(t: Tree): Boolean = t.exists {
case c: ClassDef if hasTrigger(c.mods) => true
case m: ModuleDef if hasTrigger(m.mods) => true
case _ => false
}
private def hasTrigger(mods: Modifiers): Boolean =
Triggers.exists(mods.hasAnnotationNamed)
private def extractTrigger(c: ClassDef): (ClassDef, List[Tree]) = {
val trigger = getTriggers(c.mods.annotations)
//val mods = c.mods.mapAnnotations { anns => anns.filterNot(isNamed(_, Trigger)) }
// if we remove the annotation, like a macro annotation, we end up with a
// compiler warning saying that the annotation is unused. Perhaps we could
// remove it after such warnings are emitted.
//val update = treeCopy.ClassDef(c, mods, c.name, c.tparams, c.impl)
val update = c
(update, trigger)
}
private def extractTrigger(m: ModuleDef): (ModuleDef, List[Tree]) = {
val trigger = getTriggers(m.mods.annotations)
//val mods = m.mods.mapAnnotations { anns => anns.filterNot(isNamed(_, Trigger)) }
//val update = treeCopy.ModuleDef(m, mods, m.name, m.impl)
val update = m
(update, trigger)
}
private def getTriggers(anns: List[Tree]): List[Tree] =
anns.filter(a => Triggers.exists(isNamed(a, _)))
private def isNamed(t: Tree, name: TypeName) = t match {
case Apply(Select(New(Ident(`name`)), _), _) => true
case Apply(Select(New(Select(_, `name`)), _), _) => true
case _ => false
}
/** generates a zero-functionality companion for a class */
private def genCompanion(clazz: ClassDef): ModuleDef = {
val mods =
if (clazz.mods.hasFlag(Flag.PRIVATE))
Modifiers(Flag.PRIVATE, clazz.mods.privateWithin)
else if (clazz.mods.hasFlag(Flag.PROTECTED))
Modifiers(Flag.PROTECTED, clazz.mods.privateWithin)
else NoMods
val isCase = clazz.mods.hasFlag(Flag.CASE)
lazy val accessors = clazz.impl.collect {
case ValDef(mods, _, tpt, _) if mods.hasFlag(Flag.CASEACCESSOR) =>
tpt.duplicate
}
def sup =
if (isCase &&
clazz.tparams.isEmpty &&
addSuperFunction(clazz) &&
accessors.size <= 22) {
AppliedTypeTree(
Select(
Select(Ident(nme.ROOTPKG), nme.scala_),
TypeName(s"Function${accessors.size}")
),
accessors ::: List(Ident(clazz.name))
)
} else
Select(Ident(nme.scala_), nme.AnyRef.toTypeName)
def toString_ =
DefDef(
Modifiers(Flag.OVERRIDE | Flag.SYNTHETIC),
nme.toString_,
Nil,
Nil,
Select(Select(Ident(nme.java), nme.lang), nme.String.toTypeName),
Literal(Constant(clazz.name.companionName.decode))
)
val cons = DefDef(
Modifiers(Flag.SYNTHETIC),
nme.CONSTRUCTOR,
Nil,
List(Nil),
TypeTree(),
Block(List(pendingSuperCall), Literal(Constant(())))
)
ModuleDef(
mods | Flag.SYNTHETIC,
clazz.name.companionName,
Template(
List(sup),
noSelfType,
cons :: (if (isCase) List(toString_) else Nil)
)
)
}
// responds to visiting all the parts of the tree and passes to decepticons
// to do the rewrites
def autobots(tree: Tree): Tree = tree match {
case t: PackageDef if hasTrigger(t) =>
val updated = decepticons(t.stats)
treeCopy.PackageDef(t, t.pid, updated)
case t: ModuleDef if hasTrigger(t.impl) =>
val update = treeCopy.Template(
t.impl,
t.impl.parents,
t.impl.self,
decepticons(t.impl.body)
)
treeCopy.ModuleDef(
t,
t.mods,
t.name,
update
)
case t: ClassDef if hasTrigger(t.impl) =>
// yuck, this finds classes and modules defined inside other classes.
// added for completeness.
val update = treeCopy.Template(
t.impl,
t.impl.parents,
t.impl.self,
decepticons(t.impl.body)
)
treeCopy.ClassDef(
t,
t.mods,
t.name,
t.tparams,
update
)
case t => t
}
// does not recurse, let the autobots handle that
def decepticons(trees: List[Tree]): List[Tree] = {
val classes: Map[TypeName, ClassDef] = trees.collect {
case c: ClassDef => c.name -> c
}(breakOut)
val modules: Map[TermName, ModuleDef] = trees.collect {
case m: ModuleDef => m.name -> m
}(breakOut)
object ClassNoCompanion {
def unapply(t: Tree): Option[ClassDef] = t match {
case c: ClassDef if !modules.contains(c.name.companionName) =>
Some(c)
case _ => None
}
}
object ClassHasCompanion {
def unapply(t: Tree): Option[ClassDef] = t match {
case c: ClassDef if modules.contains(c.name.companionName) =>
Some(c)
case _ => None
}
}
object CompanionAndClass {
def unapply(t: Tree): Option[(ModuleDef, ClassDef)] = t match {
case m: ModuleDef =>
classes.get(m.name.companionName).map { c =>
(m, c)
}
case _ => None
}
}
trees.flatMap {
case ClassNoCompanion(c) if hasTrigger(c.mods) =>
val companion = genCompanion(c).withAllPos(c.pos)
val (cleaned, ann) = extractTrigger(c)
val updatedCompanion = updateCompanion(ann, cleaned, companion)
List(updateClass(ann, cleaned), updatedCompanion)
case ClassHasCompanion(c) if hasTrigger(c.mods) =>
val (cleaned, ann) = extractTrigger(c)
List(updateClass(ann, cleaned))
case CompanionAndClass(companion, c) if hasTrigger(c.mods) =>
val (cleaned, ann) = extractTrigger(c)
List(updateCompanion(ann, cleaned, companion))
case m: ModuleDef if hasTrigger(m.mods) =>
val (cleaned, ann) = extractTrigger(m)
List(updateModule(ann, cleaned))
case tr =>
List(tr)
}
}
}
override lazy val components: List[PluginComponent] = List(phase)
}
