+ slick #1334 add DBIOAction.collect

slick-testkit/src/main/scala/com/typesafe/slick/testkit/tests/ActionTest.scala

@@ -144,4 +144,32 @@ class ActionTest extends AsyncTest[RelationalTestDB] {
         _ = result shouldBe 2
       } yield ()
     }
+
+  def testCollect = {
+    class T(tag: Tag) extends Table[Int](tag, u"t") {
+      def a = column[Int]("a")
+
+      def * = a
+    }
+    val ts = TableQuery[T]
+    for {
+      _ <- db.run {
+        ts.schema.create >>
+          (ts ++= Seq(2, 3, 1, 5, 4))
+      }
+      q1 = ts.sortBy(_.a).map(_.a).take(1)
+      result <- db.run(q1.result.headOption.collect {
+        case Some(a) => a
+      })
+      _ = result shouldBe 1
+      _ = result shouldFail { _ =>
+        val future = db.run(q1.result.headOption.collect {
+          case None => ()
+        })
+        import scala.concurrent.duration.Duration
+        import scala.concurrent.Await
+        Await.result(future, Duration.Inf)
+      }
+    } yield ()
+  }
 }

slick/src/main/scala/slick/dbio/DBIOAction.scala

@@ -109,6 +109,13 @@ sealed trait DBIOAction[+R, +S <: NoStream, -E <: Effect] extends Dumpable {
   def withFilter(p: R => Boolean)(implicit executor: ExecutionContext): DBIOAction[R, NoStream, E] =
     flatMap(v => if(p(v)) SuccessAction(v) else throw new NoSuchElementException("Action.withFilter failed"))
 
+  /** Transform the result of a successful execution of this action, if the given partial function is defined at that value,
+    * otherwise, the result DBIOAction will fail with a `NoSuchElementException`.
+    *
+    * If this action fails, the resulting action also fails. */
+  def collect[R2](pf: PartialFunction[R,R2])(implicit executor: ExecutionContext): DBIOAction[R2, NoStream, E] =
+    map(r1 => pf.applyOrElse(r1,(r:R) => throw new NoSuchElementException(s"DBIOAction.collect partial function is not defined at: $r")))
+
   /** Return an action which contains the Throwable with which this action failed as its result.
     * If this action succeeded, the resulting action fails with a NoSuchElementException. */
   def failed: DBIOAction[Throwable, NoStream, E] = FailedAction[E](this)