[Repo Assist] [Python] Fix CLIEvent property causing unimplementable abstract Protocol member in object expressions (#4492)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Co-authored-by: Dag Brattli <dag@brattli.net>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 4 people

src/Fable.Cli/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+* [Python] Fix object expressions implementing interfaces with `[<CLIEvent>]` members no longer produce unimplementable abstract Protocol members (fixes #3039)
+
 ## 5.0.0-rc.7 - 2026-04-07
 
 ### Added

src/Fable.Compiler/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+* [Python] Fix object expressions implementing interfaces with `[<CLIEvent>]` members no longer produce unimplementable abstract Protocol members (fixes #3039)
+
 ## 5.0.0-rc.13 - 2026-04-07
 
 ### Added

src/Fable.Transforms/Python/Fable2Python.Transforms.fs

@@ -4428,6 +4428,24 @@ let transformInterface (com: IPythonCompiler) ctx (classEnt: Fable.Entity) (_cla
             |> List.filter (fun memb -> gr.Length = 1 || (memb.IsGetter || memb.IsSetter))
         )
 
+    // [<CLIEvent>] properties are represented in FCS as both an event property getter (e.g.
+    // "Event" with CompiledName "get_Event") and add_/remove_ accessor methods. Object
+    // expressions only implement the add_/remove_ methods, so we must exclude the event
+    // property getter from the Protocol to avoid an unimplementable abstract member.
+    let eventPropertyNames =
+        members
+        |> List.choose (fun m ->
+            if m.CompiledName.StartsWith("add_", System.StringComparison.Ordinal) then
+                Some(m.CompiledName.Substring(4))
+            else
+                None
+        )
+        |> Set.ofList
+
+    let members =
+        members
+        |> List.filter (fun m -> not (eventPropertyNames.Contains(m.DisplayName)))
+
     let classMembers =
         [
             for memb in members do

tests/Python/TestEvent.fs

@@ -225,23 +225,23 @@ let ``test Classes can trigger CLI events on interfaces`` () =
     equal 5 result
     equal (box classWithEvent) sender
 
-// [<Fact>]
-// let ``test Generic interface expression can have CLI events`` () =
-//     let mutable actualSender = ""
-//     let mutable result = false
-//     let event = Event<_,_>()
-//     let ifaceWIthEvent =
-//         { new InterfaceWithCLIEvent<_> with
-//             [<CLIEvent>]
-//             member _.Event = event.Publish }
-//     ifaceWIthEvent.Event.AddHandler(fun sender arg ->
-//         actualSender <- string sender
-//         result <- arg)
-//     let expectedSender = "SENDER"
-//     let expectedResult = true
-//     event.Trigger(expectedSender, expectedResult)
-//     equal expectedSender actualSender
-//     equal expectedResult result
+[<Fact>]
+let ``test Generic interface expression can have CLI events`` () = // See #3039
+    let mutable actualSender = ""
+    let mutable result = false
+    let event = Event<_,_>()
+    let ifaceWIthEvent =
+        { new InterfaceWithCLIEvent<_> with
+            [<CLIEvent>]
+            member _.Event = event.Publish }
+    ifaceWIthEvent.Event.AddHandler(fun sender arg ->
+        actualSender <- string sender
+        result <- arg)
+    let expectedSender = "SENDER"
+    let expectedResult = true
+    event.Trigger(expectedSender, expectedResult)
+    equal expectedSender actualSender
+    equal expectedResult result
 
 [<Fact>]
 let ``test Events are unsubscribed correctly`` () = // See #609