From 94cf161cb2a328b3c727c43e43542a6e33338596 Mon Sep 17 00:00:00 2001
From: Maxime Mangel <me@mangelmaxime.fr>
Date: Fri, 25 Oct 2024 23:19:35 +0200
Subject: [PATCH] [JS/TS] Fix regression, generate `let` variable when using
 `import` on a private mutable variable (#3941)

---
 src/Fable.Cli/CHANGELOG.md                      |  1 +
 src/Fable.Transforms/FSharp2Fable.fs            |  2 +-
 .../data/import/PrivateMutableImport.fs         | 12 ++++++++++++
 .../import/PrivateMutableImport.js.expected     |  4 ++++
 .../Integration/data/import/import.fsproj       | 17 +++++++++++++++++
 5 files changed, 35 insertions(+), 1 deletion(-)
 create mode 100644 tests/Integration/Integration/data/import/PrivateMutableImport.fs
 create mode 100644 tests/Integration/Integration/data/import/PrivateMutableImport.js.expected
 create mode 100644 tests/Integration/Integration/data/import/import.fsproj

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index 22e32d739..240427a31 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -23,6 +23,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * [Rust] Fixed try finally handler order of execution (by @ncave)
 * [JS/TS/Python/Rust] Fixed String.StartsWith/EndsWith (#3934) (by @ncave)
 * [All/Rust] Removed Regex.Replace from hot paths (by @ncave)
+* [JS] Fix regression, generate `let` variable when using `import` on a private mutable variable (by @MangelMaxime)
 
 ## 4.22.0 - 2024-10-02
 
diff --git a/src/Fable.Transforms/FSharp2Fable.fs b/src/Fable.Transforms/FSharp2Fable.fs
index b4e46594c..c3502d2f2 100644
--- a/src/Fable.Transforms/FSharp2Fable.fs
+++ b/src/Fable.Transforms/FSharp2Fable.fs
@@ -1579,7 +1579,7 @@ let private transformImportValue com r typ name (memb: FSharpMemberOrFunctionOrV
         "Imported members cannot be mutable and public, please make it private: " + name
         |> addError com [] None
 
-    let memberRef = Fable.GeneratedMember.Value(name, typ)
+    let memberRef = Fable.GeneratedMember.Value(name, typ, isMutable = memb.IsMutable)
     transformImport com r typ name [] memberRef selector path
 
 let private transformMemberValue
diff --git a/tests/Integration/Integration/data/import/PrivateMutableImport.fs b/tests/Integration/Integration/data/import/PrivateMutableImport.fs
new file mode 100644
index 000000000..d9b7964a0
--- /dev/null
+++ b/tests/Integration/Integration/data/import/PrivateMutableImport.fs
@@ -0,0 +1,12 @@
+module PrivateMutableImport
+
+open Fable.Core.JsInterop
+
+type ToastrOptions =
+    abstract Thing : string with get, set
+
+[<RequireQualifiedAccess>]
+module Toastr =
+    let mutable private theOptions: ToastrOptions =
+        //()
+        import "path" "toastr"
diff --git a/tests/Integration/Integration/data/import/PrivateMutableImport.js.expected b/tests/Integration/Integration/data/import/PrivateMutableImport.js.expected
new file mode 100644
index 000000000..3d4cd6c4e
--- /dev/null
+++ b/tests/Integration/Integration/data/import/PrivateMutableImport.js.expected
@@ -0,0 +1,4 @@
+import { path } from "toastr";
+
+export let Toastr_theOptions = path;
+
diff --git a/tests/Integration/Integration/data/import/import.fsproj b/tests/Integration/Integration/data/import/import.fsproj
new file mode 100644
index 000000000..1a4c4915c
--- /dev/null
+++ b/tests/Integration/Integration/data/import/import.fsproj
@@ -0,0 +1,17 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <RollForward>Major</RollForward>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="PrivateMutableImport.fs" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Fable.Core" Version="4.2.0" />
+  </ItemGroup>
+
+</Project>