From 73b24681c597ff96fc2866d13df8dbd787c689f7 Mon Sep 17 00:00:00 2001
From: Eugene Yokota <eed3si9n@gmail.com>
Date: Mon, 30 Jan 2017 19:20:06 -0500
Subject: [PATCH] Implements registerStringCodec

Uses TypeTag to recover the full name of type parameter, which is calculated by StringTypeTag. This is sent along in ObjectEvent.
On the other end, we can lookup typeclass instances using the tag key.
---
 .../src/main/scala/sbt/internal/util/INode.scala     |  2 +-
 .../src/main/scala/sbt/internal/util/Settings.scala  | 11 ++++++-----
 .../src/main/scala/sbt/internal/util/Show.scala      |  8 --------
 .../src/main/scala/sbt/util/Show.scala               | 12 ++++++++++++
 .../scala/sbt/{internal => }/util/ShowLines.scala    |  2 +-
 .../src/test/scala/SettingsExample.scala             |  9 ++++++---
 6 files changed, 26 insertions(+), 18 deletions(-)
 delete mode 100644 internal/util-collection/src/main/scala/sbt/internal/util/Show.scala
 create mode 100644 internal/util-collection/src/main/scala/sbt/util/Show.scala
 rename internal/util-collection/src/main/scala/sbt/{internal => }/util/ShowLines.scala (92%)

diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/INode.scala b/internal/util-collection/src/main/scala/sbt/internal/util/INode.scala
index d85cadf3f..3c159ec11 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/INode.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/INode.scala
@@ -95,7 +95,7 @@ abstract class EvaluateSettings[Scope] {
       keyString
 
     private[this] def keyString =
-      (static.toSeq.flatMap { case (key, value) => if (value eq this) init.showFullKey(key) :: Nil else Nil }).headOption getOrElse "non-static"
+      (static.toSeq.flatMap { case (key, value) => if (value eq this) init.showFullKey.show(key) :: Nil else Nil }).headOption getOrElse "non-static"
 
     final def get: T = synchronized {
       assert(value != null, toString + " not evaluated")
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
index 97117e2dc..afa02c150 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
+++ b/internal/util-collection/src/main/scala/sbt/internal/util/Settings.scala
@@ -6,6 +6,7 @@ package sbt.internal.util
 import scala.language.existentials
 
 import Types._
+import sbt.util.Show
 
 sealed trait Settings[Scope] {
   def data: Map[Scope, AttributeMap]
@@ -119,7 +120,7 @@ trait Init[Scope] {
   def mapScope(f: Scope => Scope): MapScoped = new MapScoped {
     def apply[T](k: ScopedKey[T]): ScopedKey[T] = k.copy(scope = f(k.scope))
   }
-  private final class InvalidReference(val key: ScopedKey[_]) extends RuntimeException("Internal settings error: invalid reference to " + showFullKey(key))
+  private final class InvalidReference(val key: ScopedKey[_]) extends RuntimeException("Internal settings error: invalid reference to " + showFullKey.show(key))
 
   private[this] def applyDefaults(ss: Seq[Setting[_]]): Seq[Setting[_]] =
     {
@@ -215,11 +216,11 @@ trait Init[Scope] {
     {
       val guessed = guessIntendedScope(validKeys, delegates, u.referencedKey)
       val derived = u.defining.isDerived
-      val refString = display(u.defining.key)
+      val refString = display.show(u.defining.key)
       val sourceString = if (derived) "" else parenPosString(u.defining)
-      val guessedString = if (derived) "" else guessed.map(g => "\n     Did you mean " + display(g) + " ?").toList.mkString
+      val guessedString = if (derived) "" else guessed.map(g => "\n     Did you mean " + display.show(g) + " ?").toList.mkString
       val derivedString = if (derived) ", which is a derived setting that needs this key to be defined in this scope." else ""
-      display(u.referencedKey) + " from " + refString + sourceString + derivedString + guessedString
+      display.show(u.referencedKey) + " from " + refString + sourceString + derivedString + guessedString
     }
   private[this] def parenPosString(s: Setting[_]): String =
     s.positionString match { case None => ""; case Some(s) => " (" + s + ")" }
@@ -255,7 +256,7 @@ trait Init[Scope] {
       new Uninitialized(keys, prefix + suffix + " to undefined setting" + suffix + ": " + keysString + "\n ")
     }
   final class Compiled[T](val key: ScopedKey[T], val dependencies: Iterable[ScopedKey[_]], val settings: Seq[Setting[T]]) {
-    override def toString = showFullKey(key)
+    override def toString = showFullKey.show(key)
   }
   final class Flattened(val key: ScopedKey[_], val dependencies: Iterable[ScopedKey[_]])
 
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/Show.scala b/internal/util-collection/src/main/scala/sbt/internal/util/Show.scala
deleted file mode 100644
index 4a0343ed7..000000000
--- a/internal/util-collection/src/main/scala/sbt/internal/util/Show.scala
+++ /dev/null
@@ -1,8 +0,0 @@
-package sbt.internal.util
-
-trait Show[T] {
-  def apply(t: T): String
-}
-object Show {
-  def apply[T](f: T => String): Show[T] = new Show[T] { def apply(t: T): String = f(t) }
-}
\ No newline at end of file
diff --git a/internal/util-collection/src/main/scala/sbt/util/Show.scala b/internal/util-collection/src/main/scala/sbt/util/Show.scala
new file mode 100644
index 000000000..20ac0565d
--- /dev/null
+++ b/internal/util-collection/src/main/scala/sbt/util/Show.scala
@@ -0,0 +1,12 @@
+package sbt.util
+
+trait Show[A] {
+  def show(a: A): String
+}
+object Show {
+  def apply[A](f: A => String): Show[A] = new Show[A] { def show(a: A): String = f(a) }
+
+  def fromToString[A]: Show[A] = new Show[A] {
+    def show(a: A): String = a.toString
+  }
+}
diff --git a/internal/util-collection/src/main/scala/sbt/internal/util/ShowLines.scala b/internal/util-collection/src/main/scala/sbt/util/ShowLines.scala
similarity index 92%
rename from internal/util-collection/src/main/scala/sbt/internal/util/ShowLines.scala
rename to internal/util-collection/src/main/scala/sbt/util/ShowLines.scala
index f99a1394c..65729d747 100644
--- a/internal/util-collection/src/main/scala/sbt/internal/util/ShowLines.scala
+++ b/internal/util-collection/src/main/scala/sbt/util/ShowLines.scala
@@ -1,4 +1,4 @@
-package sbt.internal.util
+package sbt.util
 
 trait ShowLines[A] {
   def showLines(a: A): Seq[String]
diff --git a/internal/util-collection/src/test/scala/SettingsExample.scala b/internal/util-collection/src/test/scala/SettingsExample.scala
index cf65d6c68..20536a5ef 100644
--- a/internal/util-collection/src/test/scala/SettingsExample.scala
+++ b/internal/util-collection/src/test/scala/SettingsExample.scala
@@ -1,5 +1,7 @@
 package sbt.internal.util
 
+import sbt.util.Show
+
 /** Define our settings system */
 
 // A basic scope indexed by an integer.
@@ -12,9 +14,10 @@ final case class Scope(nestIndex: Int, idAtIndex: Int = 0)
 //  That would be a general pain.)
 case class SettingsExample() extends Init[Scope] {
   // Provides a way of showing a Scope+AttributeKey[_]
-  val showFullKey: Show[ScopedKey[_]] = new Show[ScopedKey[_]] {
-    def apply(key: ScopedKey[_]) = s"${key.scope.nestIndex}(${key.scope.idAtIndex})/${key.key.label}"
-  }
+  val showFullKey: Show[ScopedKey[_]] = Show[ScopedKey[_]]((key: ScopedKey[_]) =>
+    {
+      s"${key.scope.nestIndex}(${key.scope.idAtIndex})/${key.key.label}"
+    })
 
   // A sample delegation function that delegates to a Scope with a lower index.
   val delegates: Scope => Seq[Scope] = {