Add prettyPrint method to Target

This adds a pretty printer for firrtl.annotation.Target and associated
tests. This uses a tree-like output where the following target
~Circuit|Module/foo:Foo>ref.field[0] will serialize to:

  circuit Circuit:
  └── module Module:
      └── foo of Foo:
          └── ref.field[0]

This enables better error messages and a human readable syntax better than
the existing serialize method (and avoiding the need for users to
understand the Target serialization syntax), but that is not intended to
be deserialized nor space efficient.

Signed-off-by: Schuyler Eldridge <schuyler.eldridge@ibm.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/annotations/Target.scala b/src/main/scala/firrtl/annotations/Target.scala
index dcf5cb02..8a9d68e8 100644
--- a/src/main/scala/firrtl/annotations/Target.scala
+++ b/src/main/scala/firrtl/annotations/Target.scala
@@ -55,6 +55,32 @@ sealed trait Target extends Named {
     }
   }
 
+  /** Pretty serialization, ideal for error messages. Cannot be deserialized.
+    * @return Human-readable serialization
+    */
+  def prettyPrint(tab: String = ""): String = {
+    val circuitString = s"""${tab}circuit ${circuitOpt.getOrElse("???")}:"""
+    val moduleString = s"""\n$tab└── module ${moduleOpt.getOrElse("???")}:"""
+    var depth = 4
+    val tokenString = tokens.map {
+      case Ref(r) => val rx = s"""\n$tab${" "*depth}└── $r"""; depth += 4; rx
+      case Instance(i) => val ix = s"""\n$tab${" "*depth}└── inst $i """; ix
+      case OfModule(o) => val ox = s"of $o:"; depth += 4; ox
+      case Field(f) => s".$f"
+      case Index(v) => s"[$v]"
+      case Clock => s"@clock"
+      case Reset => s"@reset"
+      case Init => s"@init"
+    }.mkString("")
+
+    (moduleOpt.isEmpty, tokens.isEmpty) match {
+      case (true, true) => circuitString
+      case (_, true) => circuitString + moduleString
+      case (_, _) => circuitString + moduleString + tokenString
+    }
+  }
+
+
   /** @return Converts this [[Target]] into a [[GenericTarget]] */
   def toGenericTarget: GenericTarget = GenericTarget(circuitOpt, moduleOpt, tokens.toVector)