Completion for build-level keys

sbt's shell provided completion only for keys that were relative to a
defined project, but didn't provide completion for keys that belong to
the build definition only.

This commit fixes this issue by defining a new kind of `Parser` (from
which completions are generated) which runs its input simultaneously on
distinct parsers. We now define a parser for project-level keys and
another parser for build-level keys. These two parsers are eventually
combined, and we get the completions of both parsers.

Fixes sbt/sbt#2460

main/src/main/scala/sbt/Act.scala

@@ -48,12 +48,22 @@ object Act {
           new ParsedKey(makeScopedKey(proj, conf, task, extra, key), mask)
         }
 
-      for {
-        rawProject <- optProjectRef(index, current)
-        proj = resolveProject(rawProject, current)
-        confAmb <- config(index configs proj)
-        partialMask = ScopeMask(rawProject.isExplicit, confAmb.isExplicit, false, false)
-      } yield taskKeyExtra(proj, confAmb, partialMask)
+      val projectKeys =
+        for {
+          rawProject <- optProjectRef(index, current)
+          proj = resolveProject(rawProject, current)
+          confAmb <- config(index configs proj)
+          partialMask = ScopeMask(rawProject.isExplicit, confAmb.isExplicit, false, false)
+        } yield taskKeyExtra(proj, confAmb, partialMask)
+
+      val build = Some(BuildRef(current.build))
+      val buildKeys =
+        for {
+          confAmb <- config(index configs build)
+          partialMask = ScopeMask(false, confAmb.isExplicit, false, false)
+        } yield taskKeyExtra(build, confAmb, partialMask)
+
+      buildKeys combinedWith projectKeys map (_.flatten)
     }
   def makeScopedKey(proj: Option[ResolvedReference], conf: Option[String], task: Option[AttributeKey[_]], extra: ScopeAxis[AttributeMap], key: AttributeKey[_]): ScopedKey[_] =
     ScopedKey(Scope(toAxis(proj, Global), toAxis(conf map ConfigKey.apply, Global), toAxis(task, Global), extra), key)

util/complete/src/main/scala/sbt/complete/Parser.scala

@@ -126,6 +126,9 @@ sealed trait RichParser[A] {
 
   /** Applies the original parser, applies `f` to the result to get the next parser, and applies that parser and uses its result for the overall result. */
   def flatMap[B](f: A => Parser[B]): Parser[B]
+
+  /** Applied both the original parser and `b` on the same input and returns the results produced by each parser */
+  def combinedWith(b: Parser[A]): Parser[Seq[A]]
 }
 
 /** Contains Parser implementation helper methods not typically needed for using parsers. */
@@ -229,6 +232,12 @@ object Parser extends ParserMain {
       }
     }
 
+  def combinedParser[A](a: Parser[A], b: Parser[A]): Parser[Seq[A]] =
+    if (a.valid)
+      if (b.valid) new CombiningParser(a, b) else a.map(Seq(_))
+    else
+      b.map(Seq(_))
+
   def choiceParser[A, B](a: Parser[A], b: Parser[B]): Parser[Either[A, B]] =
     if (a.valid)
       if (b.valid) new HetParser(a, b) else a.map(left.fn)
@@ -309,6 +318,7 @@ trait ParserMain {
     def filter(f: A => Boolean, msg: String => String): Parser[A] = filterParser(a, f, "", msg)
     def string(implicit ev: A <:< Seq[Char]): Parser[String] = map(_.mkString)
     def flatMap[B](f: A => Parser[B]) = bindParser(a, f)
+    def combinedWith(b: Parser[A]): Parser[Seq[A]] = combinedParser(a, b)
   }
 
   implicit def literalRichCharParser(c: Char): RichParser[Char] = richParser(c)
@@ -633,6 +643,24 @@ private final class HetParser[A, B](a: Parser[A], b: Parser[B]) extends ValidPar
   def completions(level: Int) = a.completions(level) ++ b.completions(level)
   override def toString = "(" + a + " || " + b + ")"
 }
+private final class CombiningParser[T](a: Parser[T], b: Parser[T]) extends ValidParser[Seq[T]] {
+  lazy val result: Option[Seq[T]] = (a.result.toSeq ++ b.result.toSeq) match { case Seq() => None; case seq => Some(seq) }
+  def completions(level: Int) = a.completions(level) ++ b.completions(level)
+  def derive(i: Char) =
+    (a.valid, b.valid) match {
+      case (true, true)   => new CombiningParser(a derive i, b derive i)
+      case (true, false)  => a derive i map (Seq(_))
+      case (false, true)  => b derive i map (Seq(_))
+      case (false, false) => new Invalid(mkFailure("No valid parser available."))
+    }
+  def resultEmpty =
+    (a.resultEmpty, b.resultEmpty) match {
+      case (Value(ra), Value(rb)) => Value(Seq(ra, rb))
+      case (Value(ra), _)         => Value(Seq(ra))
+      case (_, Value(rb))         => Value(Seq(rb))
+      case _                      => Value(Nil)
+    }
+}
 private final class ParserSeq[T](a: Seq[Parser[T]], errors: => Seq[String]) extends ValidParser[Seq[T]] {
   assert(a.nonEmpty)
   lazy val resultEmpty: Result[Seq[T]] =

util/complete/src/test/scala/ParserTest.scala

@@ -107,6 +107,15 @@ object ParserTest extends Properties("Completing Parser") {
   property("repeatDep requires at least one token") = !matches(repeat, "")
   property("repeatDep accepts one token") = matches(repeat, colors.toSeq.head)
   property("repeatDep accepts two tokens") = matches(repeat, colors.toSeq.take(2).mkString(" "))
+  property("combined parser gives completion of both parsers") = {
+    val prefix = "fix"
+    val p1Suffixes = Set("", "ated", "ation")
+    val p2Suffixes = Set("es", "ed")
+    val p1: Parser[String] = p1Suffixes map (suffix => (prefix + suffix): Parser[String]) reduce (_ | _)
+    val p2: Parser[String] = p2Suffixes map (suffix => (prefix + suffix): Parser[String]) reduce (_ | _)
+    val suggestions: Set[Completion] = p1Suffixes ++ p2Suffixes map (new Suggestion(_))
+    checkAll(prefix, p1 combinedWith p2, Completions(suggestions))
+  }
 }
 object ParserExample {
   val ws = charClass(_.isWhitespace)+