Add chained test & usage example

readme.md

@@ -62,6 +62,25 @@ var id = Sample.IdLens.Get(...);
 Sample.DescriptionLens.Set("replaced")(...);
 ```
 
+## Dealing with immutable collections & nullable properties
+
+`Visor` comes with a useful set of optics for manipulating values at nullable anr/or collection properties.
+Although `System.Collections.Immutable` is supported I strongly recommend using language-ext's immutable collections
+because standart ones breaks value equality of records.
+
+Here is a brief example of using build-in optics:
+
+```csharp
+[Optics] internal partial record InnerItem(int Id, string Name);
+[Optics] internal partial record Aux(string Comment, IImmutableList<string> Tags);
+[Optics(withNested: true)] internal partial record ItemWrapper(InnerItem Item, Aux? Aux);
+[Optics(withNested: true)] internal partial record Warehouse(ItemWrapper Main);
+
+var warehouse = new Warehouse(new ItemWrapper(new InnerItem(1, "Default"), new Aux("test", ImmutableList.Create("tag1", "tag2"))));
+var telescope = Warehouse.FocusMain.AuxLens.NotNull().Compose(Aux.TagsLens).Compose(Property.IImmutableList.First<string>());
+var warehouse2 = telescope.Set("updated_tag")(warehouse); //Now warehouse2.Main.Aux?.Tags is ("updated_tag", "tag2")
+```
+
 ## Coming soon
 - Prism
 - Traverse

src/LeviySoft.Visor.Gen.Tests/ChainedOpticTests.cs

@@ -1,5 +1,7 @@
 using Shouldly;
 using Xunit;
+using System.Collections.Immutable;
+using LeviySoft.Visor.Collections.Immutable;
 
 namespace LeviySoft.Visor.Gen.Tests;
 
@@ -14,4 +16,15 @@ public void SetIdTest()
 
         warehouse2.Main.Item.Id.ShouldBe(42);
     }
+
+    [Fact]
+    public void UpdateTagTest()
+    {
+        var warehouse = new Warehouse(new ItemWrapper(new InnerItem(1, "Default"), new Aux("test", ImmutableList.Create("tag1", "tag2"))));
+
+        var telescope = Warehouse.FocusMain.AuxLens.NotNull().Compose(Aux.TagsLens).Compose(Property.IImmutableList.First<string>());
+
+        var warehouse2 = telescope.Set("updated_tag")(warehouse);
+        warehouse2.Main.Aux?.Tags.ShouldBe(ImmutableList.Create("updated_tag", "tag2"));
+    }
 }

src/LeviySoft.Visor.Gen.Tests/Sample.cs

@@ -1,3 +1,5 @@
+using System.Collections.Immutable;
+
 namespace LeviySoft.Visor.Gen.Tests;
 
 [Optics]
@@ -8,7 +10,7 @@ internal partial record Sample(int Id, string Description, Inner Inner);
 
 [Optics] internal partial record InnerItem(int Id, string Name);
 
-[Optics] internal partial record Aux(string Comment);
+[Optics] internal partial record Aux(string Comment, IImmutableList<string> Tags);
 
 [Optics(withNested: true)] internal partial record ItemWrapper(InnerItem Item, Aux? Aux);