API: Shorten default displayName-s, use pretty default names for var …

…signals and eventbus streams

src/main/scala/com/raquo/airstream/core/Named.scala

@@ -16,7 +16,7 @@ trait Named {
   protected[this] var maybeDisplayName: js.UndefOr[String] = js.undefined
 
   /** This is the method that subclasses override to preserve the user's ability to set custom display names. */
-  protected def defaultDisplayName: String = super.toString
+  protected def defaultDisplayName: String = s"${getClass.getSimpleName}@${hashCode()}"
 
   /** Override [[defaultDisplayName]] instead of this, if you need to. */
   final override def toString: String = displayName

src/main/scala/com/raquo/airstream/eventbus/EventBus.scala

@@ -13,7 +13,7 @@ import scala.util.Try
   */
 class EventBus[A] extends EventSource[A] with Sink[A] with Named {
 
-  val writer: WriteBus[A] = new WriteBus[A]
+  val writer: WriteBus[A] = new WriteBus[A](parentDisplayName = displayName)
 
   val events: EventStream[A] = writer.stream
 

src/main/scala/com/raquo/airstream/eventbus/EventBusStream.scala

@@ -4,7 +4,9 @@ import com.raquo.airstream.common.InternalNextErrorObserver
 import com.raquo.airstream.core.{EventStream, Protected, Transaction, WritableStream}
 import com.raquo.ew.JsArray
 
-class EventBusStream[A] private[eventbus] () extends WritableStream[A] with InternalNextErrorObserver[A] {
+class EventBusStream[A] private[eventbus] (
+  parentDisplayName: => String
+) extends WritableStream[A] with InternalNextErrorObserver[A] {
 
   private val sourceStreams: JsArray[EventStream[A]] = JsArray()
 
@@ -72,4 +74,6 @@ class EventBusStream[A] private[eventbus] () extends WritableStream[A] with Inte
     sourceStreams.forEach(_.removeInternalObserver(observer = this))
     super.onStop()
   }
+
+  override protected def defaultDisplayName: String = parentDisplayName + ".events"
 }

src/main/scala/com/raquo/airstream/eventbus/WriteBus.scala

@@ -6,12 +6,15 @@ import com.raquo.airstream.util.hasDuplicateTupleKeys
 
 import scala.util.Try
 
-class WriteBus[A] extends Observer[A] {
+class WriteBus[A](
+  parentDisplayName: => String,
+  displayNameSuffix: String = ".writer"
+) extends Observer[A] {
 
   /** Hidden here because the public interface of WriteBus is all about writing
     * rather than reading, but exposed in [[EventBus]]
     */
-  private[eventbus] val stream: EventBusStream[A] = new EventBusStream()
+  private[eventbus] val stream: EventBusStream[A] = new EventBusStream(displayName)
 
   /** Note: this source will be removed when the `owner` you provide says so.
     * To remove this source manually, call .kill() on the resulting Subscription.
@@ -24,19 +27,21 @@ class WriteBus[A] extends Observer[A] {
   }
 
   def contracomposeWriter[B](operator: EventStream[B] => EventStream[A])(implicit owner: Owner): WriteBus[B] = {
-    val mapBus = new WriteBus[B]
+    val mapBus = new WriteBus[B](displayName, ".contracomposeWriter")
     addSource(mapBus.stream.compose(operator))(owner)
     mapBus
   }
 
   /** Behaves similar to `contramap`, but gives you a WriteBus, not just an Observer */
   def contramapWriter[B](project: B => A)(implicit owner: Owner): WriteBus[B] = {
-    contracomposeWriter[B](_.map(project))(owner)
+    val mapBus = new WriteBus[B](displayName, ".contramapWriter")
+    addSource(mapBus.stream.map(project))(owner)
+    mapBus
   }
 
   /** Behaves similar to `filter`, but gives you a WriteBus, not just an Observer */
   def filterWriter(passes: A => Boolean)(implicit owner: Owner): WriteBus[A] = {
-    val filterBus = new WriteBus[A]
+    val filterBus = new WriteBus[A](displayName, ".filterWriter")
     addSource(filterBus.stream.filter(passes))(owner)
     filterBus
   }
@@ -80,6 +85,8 @@ class WriteBus[A] extends Observer[A] {
       onNextWithSharedTransaction(_, sharedTransaction)
     )
   }
+
+  override protected def defaultDisplayName: String = parentDisplayName + displayNameSuffix
 }
 
 object WriteBus {

src/main/scala/com/raquo/airstream/state/DerivedVar.scala

@@ -17,12 +17,13 @@ class DerivedVar[A, B](
   parent: Var[A],
   zoomIn: A => B,
   zoomOut: (A, B) => A,
-  owner: Owner
+  owner: Owner,
+  displayNameSuffix: String
 ) extends Var[B] {
 
   override private[state] def underlyingVar: SourceVar[_] = parent.underlyingVar
 
-  private[this] val _varSignal = new DerivedVarSignal(parent, zoomIn, owner)
+  private[this] val _varSignal = new DerivedVarSignal(parent, zoomIn, owner, displayName)
 
   // #Note this getCurrentValue implementation is different from SourceVar
   //  - SourceVar's getCurrentValue looks at an internal currentValue variable
@@ -54,4 +55,6 @@ class DerivedVar[A, B](
   }
 
   override val signal: StrictSignal[B] = _varSignal
+
+  override protected def defaultDisplayName: String = parent.displayName + displayNameSuffix
 }

src/main/scala/com/raquo/airstream/state/DerivedVarSignal.scala

@@ -7,7 +7,8 @@ import com.raquo.airstream.ownership.{Owner, Subscription}
 class DerivedVarSignal[A, B](
   parent: Var[A],
   zoomIn: A => B,
-  owner: Owner
+  owner: Owner,
+  parentDisplayName: => String
 ) extends MapSignal[A, B](
   parent.signal,
   project = zoomIn,
@@ -18,4 +19,6 @@ class DerivedVarSignal[A, B](
   override protected[state] def isStarted: Boolean = super.isStarted
 
   override protected[this] val subscription: Subscription = this.addObserver(Observer.empty)(owner)
+
+  override protected def defaultDisplayName: String = parentDisplayName + ".signal"
 }

src/main/scala/com/raquo/airstream/state/SourceVar.scala

@@ -13,7 +13,10 @@ class SourceVar[A] private[state](initial: Try[A]) extends Var[A] {
   private[this] var currentValue: Try[A] = initial
 
   /** VarSignal is a private type, do not expose it */
-  private[this] val _varSignal = new VarSignal[A](initial = currentValue)
+  private[this] val _varSignal = new VarSignal[A](
+    initial = currentValue,
+    parentDisplayName = displayName
+  )
 
   override private[state] def underlyingVar: SourceVar[_] = this
 

src/main/scala/com/raquo/airstream/state/Var.scala

@@ -84,7 +84,7 @@ trait Var[A] extends SignalSource[A] with Sink[A] with Named {
   }
 
   def zoom[B](in: A => B)(out: (A, B) => A)(implicit owner: Owner): Var[B] = {
-    new DerivedVar[A, B](this, in, out, owner)
+    new DerivedVar[A, B](this, in, out, owner, displayNameSuffix = ".zoom")
   }
 
   def setTry(tryValue: Try[A]): Unit = writer.onTry(tryValue)

src/main/scala/com/raquo/airstream/state/VarSignal.scala

@@ -12,7 +12,8 @@ import scala.util.Try
   * (see StrictSignal).
   */
 private[state] class VarSignal[A] private[state](
-  initial: Try[A]
+  initial: Try[A],
+  parentDisplayName: => String
 ) extends WritableSignal[A] with StrictSignal[A] {
 
   /** SourceVar does not directly depend on other observables, so it breaks the graph. */
@@ -31,4 +32,6 @@ private[state] class VarSignal[A] private[state](
   override protected def currentValueFromParent(): Try[A] = tryNow() // noop
 
   override protected def onWillStart(): Unit = () // noop
+
+  override protected def defaultDisplayName: String = parentDisplayName + ".signal"
 }

src/test/scala/com/raquo/airstream/DebugSpec.scala

@@ -833,4 +833,46 @@ class DebugSpec extends UnitSpec with BeforeAndAfter {
 
     calculations.clear()
   }
+
+  it("EventBus.events and Var.signal display names") {
+
+    val bus = new EventBus[Int]
+
+    assert(bus.displayName.startsWith("EventBus@"))
+    assertEquals(bus.events.displayName, bus.displayName + ".writer.events")
+
+    // --
+
+    bus.setDisplayName("bus")
+
+    assertEquals(bus.writer.displayName, "bus.writer")
+    assertEquals(bus.events.displayName, "bus.writer.events")
+    assertEquals(bus.writer.contramapWriter(identity[Int]).displayName, "bus.writer.contramapWriter")
+
+    // --
+
+    val _var = Var(1)
+    val _derived = _var.zoom(x => x)((acc, x) => x)
+
+    assert(_var.displayName.startsWith("SourceVar@"))
+    assertEquals(_var.signal.displayName, _var.displayName + ".signal")
+    assertEquals(_derived.displayName, _var.displayName + ".zoom")
+    assertEquals(_derived.signal.displayName, _derived.displayName + ".signal")
+
+    // --
+
+    _var.setDisplayName("var")
+
+    assertEquals(_var.displayName, "var")
+    assertEquals(_var.signal.displayName, "var.signal")
+    assertEquals(_derived.displayName, _var.displayName + ".zoom")
+    assertEquals(_derived.signal.displayName, _derived.displayName + ".signal")
+
+    // --
+
+    _derived.setDisplayName("zoomed")
+
+    assertEquals(_derived.displayName, "zoomed")
+    assertEquals(_derived.signal.displayName, _derived.displayName + ".signal")
+  }
 }