From 746a80e5cb6d1de1e3e85b6855847bd3a16f5ce0 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9=20Larivi=C3=A8re?=
 <timothe.lariviere@kanoyatech.com>
Date: Wed, 14 Feb 2024 16:10:35 +0100
Subject: [PATCH 1/2] Lock access to fn in Cmd.debounce to avoid null crash

---
 src/Fabulous/Cmd.fs | 36 ++++++++++++++++++++----------------
 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/src/Fabulous/Cmd.fs b/src/Fabulous/Cmd.fs
index 2c01fb7ad..0cadd9c87 100644
--- a/src/Fabulous/Cmd.fs
+++ b/src/Fabulous/Cmd.fs
@@ -194,19 +194,23 @@ module Cmd =
 
         fun (value: 'value) ->
             [ fun dispatch ->
-                  if cts <> null then
-                      cts.Cancel()
-                      cts.Dispose()
-
-                  cts <- new CancellationTokenSource()
-
-                  Async.Start(
-                      async {
-                          do! Async.Sleep(timeout)
-                          dispatch(fn value)
-
-                          cts.Dispose()
-                          cts <- null
-                      },
-                      cts.Token
-                  ) ]
+                lock fn (fun () ->
+                    if cts <> null then
+                        cts.Cancel()
+                        cts.Dispose()
+
+                    cts <- new CancellationTokenSource()
+
+                    Async.Start(
+                        async {
+                            do! Async.Sleep(timeout)
+                            lock fn (fun () ->
+                                dispatch(fn value)
+
+                                if cts <> null then
+                                    cts.Dispose()
+                                    cts <- null
+                            )
+                        },
+                        cts.Token
+                    ) ) ]

From 1045e0388b8f85bc6f8bd78e5ef3f570ac0af054 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timoth=C3=A9=20Larivi=C3=A8re?=
 <timothe.lariviere@kanoyatech.com>
Date: Wed, 14 Feb 2024 16:34:03 +0100
Subject: [PATCH 2/2] Change to lock object

---
 src/Fabulous/Cmd.fs | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/src/Fabulous/Cmd.fs b/src/Fabulous/Cmd.fs
index 0cadd9c87..4a4b96956 100644
--- a/src/Fabulous/Cmd.fs
+++ b/src/Fabulous/Cmd.fs
@@ -190,27 +190,28 @@ module Cmd =
 
     /// Command to issue a message if no other message has been issued within the specified timeout
     let debounce (timeout: int) (fn: 'value -> 'msg) : 'value -> Cmd<'msg> =
+        let funLock = obj()
         let mutable cts: CancellationTokenSource = null
 
         fun (value: 'value) ->
             [ fun dispatch ->
-                lock fn (fun () ->
-                    if cts <> null then
-                        cts.Cancel()
-                        cts.Dispose()
-
-                    cts <- new CancellationTokenSource()
-
-                    Async.Start(
-                        async {
-                            do! Async.Sleep(timeout)
-                            lock fn (fun () ->
-                                dispatch(fn value)
-
-                                if cts <> null then
-                                    cts.Dispose()
-                                    cts <- null
-                            )
-                        },
-                        cts.Token
-                    ) ) ]
+                  lock funLock (fun () ->
+                      if cts <> null then
+                          cts.Cancel()
+                          cts.Dispose()
+
+                      cts <- new CancellationTokenSource()
+
+                      Async.Start(
+                          async {
+                              do! Async.Sleep(timeout)
+
+                              lock funLock (fun () ->
+                                  dispatch(fn value)
+
+                                  if cts <> null then
+                                      cts.Dispose()
+                                      cts <- null)
+                          },
+                          cts.Token
+                      )) ]