Merge pull request #1069 from fabulous-dev/destroy-component-on-arg-change

Recreate component on arg change

Author: TimLariviere

CHANGELOG.md

@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 _No unreleased changes_
 
+## [2.5.0-pre11] - 2024-02-19
+
+### Fixed
+- Recreate component on arg change by @TimLariviere (https://github.com/fabulous-dev/Fabulous/pull/1069)
+
 ## [2.5.0-pre10] - 2024-02-19
 
 ### Fixed
@@ -105,7 +110,8 @@ _No unreleased changes_
 ### Changed
 - Fabulous.XamarinForms & Fabulous.MauiControls have been moved been out of the Fabulous repository. Find them in their own repositories: [https://github.com/fabulous-dev/Fabulous.XamarinForms](https://github.com/fabulous-dev/Fabulous.XamarinForms) / [https://github.com/fabulous-dev/Fabulous.MauiControls](https://github.com/fabulous-dev/Fabulous.MauiControls)
 
-[unreleased]: https://github.com/fabulous-dev/Fabulous/compare/2.5.0-pre10...HEAD
+[unreleased]: https://github.com/fabulous-dev/Fabulous/compare/2.5.0-pre11...HEAD
+[2.5.0-pre11]: https://github.com/fabulous-dev/Fabulous/releases/tag/2.5.0-pre11
 [2.5.0-pre10]: https://github.com/fabulous-dev/Fabulous/releases/tag/2.5.0-pre10
 [2.5.0-pre9]: https://github.com/fabulous-dev/Fabulous/releases/tag/2.5.0-pre9
 [2.5.0-pre8]: https://github.com/fabulous-dev/Fabulous/releases/tag/2.5.0-pre8

src/Fabulous/MvuComponent.fs

@@ -1,5 +1,6 @@
 namespace Fabulous
 
+open System
 open System.Runtime.CompilerServices
 
 [<Struct; NoEquality; NoComparison>]
@@ -89,6 +90,20 @@ module MvuComponent =
     let Data =
         Attributes.defineSimpleScalar<MvuComponentData> "MvuComponent_Data" ScalarAttributeComparers.noCompare (fun _ _ _ -> ())
 
+    let canReuseMvuComponent (prev: Widget) (curr: Widget) =
+        let prevData =
+            match prev.ScalarAttributes with
+            | ValueSome attrs when attrs.Length > 0 -> attrs[0].Value :?> MvuComponentData
+            | _ -> failwith "Component widget must have a body"
+
+        let currData =
+            match curr.ScalarAttributes with
+            | ValueSome attrs when attrs.Length > 0 -> attrs[0].Value :?> MvuComponentData
+            | _ -> failwith "Component widget must have a body"
+
+        // NOTE: Somehow using = here crashes the app and prevents debugging...
+        Object.Equals(prevData.Arg, currData.Arg)
+
 /// Delegate used by the MvuComponentBuilder to compose a component body
 /// It will be aggressively inlined by the compiler leaving no overhead, only a pure function that returns a WidgetBuilder
 type MvuComponentBodyBuilder<'msg, 'marker> =

src/Fabulous/View.fs

@@ -8,6 +8,8 @@ module ViewHelpers =
             false
         else if (prevKey = Memo.MemoWidgetKey) then
             Memo.canReuseMemoizedWidget prevWidget currWidget
+        else if (prevKey = MvuComponent.WidgetKey) then
+            MvuComponent.canReuseMvuComponent prevWidget currWidget
         else
             true