Merge pull request #418 from JetBrains/im/357.mapped-property-advise

(#357) MappedProperty: should produce the current value on Advise

Author: Iliya-usov

rd-net/Lifetimes/Collections/Viewable/ReactiveEx.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Threading.Tasks;
 using JetBrains.Core;
 using JetBrains.Lifetimes;
@@ -378,7 +377,7 @@ public MappedProperty(IViewableProperty<T> source, Func<T, R> map)
         Change = new MappedSink<T, R>(source.Change, myMap);
       }
 
-      public void Advise(Lifetime lifetime, Action<R> handler) => Change.Advise(lifetime, handler);
+      public void Advise(Lifetime lifetime, Action<R> handler) => mySource.Advise(lifetime, v => handler(myMap(v)));
 
       public ISource<R> Change { get; }
 
@@ -430,4 +429,4 @@ public static Task<T> NextValueAsync<T>(this ISource<T> source, Lifetime lifetim
     }
 #endif
   }
-}
+}

rd-net/Test.Lifetimes/Collections/Viewable/ViewablePropertyTest.cs

@@ -0,0 +1,30 @@
+using JetBrains.Collections.Viewable;
+using JetBrains.Lifetimes;
+using NUnit.Framework;
+
+namespace Test.Lifetimes.Collections.Viewable;
+
+public class ViewablePropertyTest
+{
+  [TestCase]
+  public void TestAdvise()
+  {
+    var prop = new ViewableProperty<int>(123);
+    Lifetime.Using(lt =>
+    {
+      int? value = null;
+      prop.Advise(lt, x => value = x);
+      Assert.AreEqual(123, value);
+    });
+    Lifetime.Using(lt =>
+    {
+      int? value = null;
+      var mapped = prop.Select(x => x + 1);
+      mapped.Advise(lt, x => value = x);
+      Assert.AreEqual(124, value);
+
+      prop.Value = 125;
+      Assert.AreEqual(126, value);
+    });
+  }
+}