From c5b684984cefa459cd3537a9446b1bc5226a202c Mon Sep 17 00:00:00 2001
From: Dale Wijnand <dale.wijnand@gmail.com>
Date: Sat, 15 Feb 2020 17:10:49 +0000
Subject: [PATCH] Tweak Def.displayRelative

My driving use case was LocalProject: it should display the same as a
fully resolved ProjectRef.  Similarly ThisBuild should display as such.
---
 main-settings/src/main/scala/sbt/Def.scala    | 19 +++++++++++++------
 .../src/test/scala/sbt/ScopeDisplaySpec.scala | 12 ++++++------
 2 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/main-settings/src/main/scala/sbt/Def.scala b/main-settings/src/main/scala/sbt/Def.scala
index 95988ebcc..0ae22de4c 100644
--- a/main-settings/src/main/scala/sbt/Def.scala
+++ b/main-settings/src/main/scala/sbt/Def.scala
@@ -10,6 +10,7 @@ package sbt
 import java.io.File
 import java.net.URI
 
+import scala.annotation.tailrec
 import sbt.KeyRanks.{ DTask, Invisible }
 import sbt.Scope.{ GlobalScope, ThisScope }
 import sbt.internal.util.Types.const
@@ -132,13 +133,19 @@ object Def extends Init[Scope] with TaskMacroExtra {
       project: Reference,
       trailingSlash: Boolean
   ): String = {
-    val trailing = if (trailingSlash) " /" else ""
-    project match {
-      case BuildRef(current.build)      => "ThisBuild" + trailing
-      case `current`                    => ""
-      case ProjectRef(current.build, x) => x + trailing
-      case _                            => Reference.display(project) + trailing
+    import Reference.{ display => displayRef }
+    @tailrec def loop(ref: Reference): String = ref match {
+      case ProjectRef(b, p) => if (b == current.build) loop(LocalProject(p)) else displayRef(ref)
+      case BuildRef(b)      => if (b == current.build) loop(ThisBuild) else displayRef(ref)
+      case RootProject(b)   => if (b == current.build) loop(LocalRootProject) else displayRef(ref)
+      case LocalProject(p)  => if (p == current.project) "" else p
+      case ThisBuild        => "ThisBuild"
+      case LocalRootProject => "<root>"
+      case ThisProject      => "<this>"
     }
+    val str = loop(project)
+    if (trailingSlash && !str.isEmpty) s"$str /"
+    else str
   }
 
   @deprecated("Use variant without multi", "1.1.1")
diff --git a/main-settings/src/test/scala/sbt/ScopeDisplaySpec.scala b/main-settings/src/test/scala/sbt/ScopeDisplaySpec.scala
index de8290196..103b62802 100644
--- a/main-settings/src/test/scala/sbt/ScopeDisplaySpec.scala
+++ b/main-settings/src/test/scala/sbt/ScopeDisplaySpec.scala
@@ -64,11 +64,11 @@ class ScopeDisplaySpec extends FlatSpec {
   it should "ProjectRef diff build" in assert(disp(p3) == """ProjectRef(uri("other"), "qux") /""")
   it should "BuildRef same build" in assert(disp(BuildRef(b1)) == "ThisBuild /")
   it should "BuildRef diff build" in assert(disp(BuildRef(b2)) == "{other} /")
-  it should "RootProject same build" in assert(disp(RootProject(b1)) == "{foo/bar }<root> /")
+  it should "RootProject same build" in assert(disp(RootProject(b1)) == "<root> /")
   it should "RootProject diff build" in assert(disp(RootProject(b2)) == "{other }<root> /")
-  it should "LocalProject curr proj" in assert(disp(LocalProject(p1.project)) == "{<this>}bar /")
-  it should "LocalProject diff proj" in assert(disp(LocalProject(p2.project)) == "{<this>}baz /")
-  it should "ThisBuild" in assert(disp(ThisBuild) == "{<this>} /")
-  it should "LocalRootProject" in assert(disp(LocalRootProject) == "{<this>}<root> /")
-  it should "ThisProject" in assert(disp(ThisProject) == "{<this>}<this> /")
+  it should "LocalProject curr proj" in assert(disp(LocalProject(p1.project)) == "")
+  it should "LocalProject diff proj" in assert(disp(LocalProject(p2.project)) == "baz /")
+  it should "ThisBuild" in assert(disp(ThisBuild) == "ThisBuild /")
+  it should "LocalRootProject" in assert(disp(LocalRootProject) == "<root> /")
+  it should "ThisProject" in assert(disp(ThisProject) == "<this> /")
 }