From 4a90f15523df8e06960bdad7101bc3fbb5985430 Mon Sep 17 00:00:00 2001
From: Maxime Mangel <me@mangelmaxime.fr>
Date: Mon, 10 Mar 2025 22:23:26 +0100
Subject: [PATCH] [TS] Sanitize DUs case names when generating constructor
 function (#4072)

Fix #4071
---
 src/Fable.Cli/CHANGELOG.md          |  1 +
 src/Fable.Compiler/CHANGELOG.md     |  1 +
 src/Fable.Transforms/Fable2Babel.fs |  4 ++--
 tests/Js/Main/UnionTypeTests.fs     | 13 ++++++++++++-
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index 762c842ec2..521745a349 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * [JS/TS] Make `nullArgCheck` report the same error message as on .NET (by @MangelMaxime)
+* [TS] Sanitize DUs case names when generating constructor function (by @MangelMaxime)
 
 ## 5.0.0-alpha.11 - 2025-03-03
 
diff --git a/src/Fable.Compiler/CHANGELOG.md b/src/Fable.Compiler/CHANGELOG.md
index a84aef339e..a4cce698d9 100644
--- a/src/Fable.Compiler/CHANGELOG.md
+++ b/src/Fable.Compiler/CHANGELOG.md
@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * [JS/TS] Make `nullArgCheck` report the same error message as on .NET (by @MangelMaxime)
+* [TS] Sanitize DUs case names when generating constructor function (by @MangelMaxime)
 
 ## 5.0.0-alpha.11 - 2025-03-03
 
diff --git a/src/Fable.Transforms/Fable2Babel.fs b/src/Fable.Transforms/Fable2Babel.fs
index d2e51ddee0..088a5a129d 100644
--- a/src/Fable.Transforms/Fable2Babel.fs
+++ b/src/Fable.Transforms/Fable2Babel.fs
@@ -1572,7 +1572,7 @@ module Util =
             if com.IsTypeScript then
                 match List.tryItem tag ent.UnionCases with
                 | Some case ->
-                    match tryJsConstructorWithSuffix com ctx ent ("_" + case.Name) with
+                    match tryJsConstructorWithSuffix com ctx ent ("_" + sanitizeName case.Name) with
                     | Some helperRef ->
                         let typeParams = makeTypeParamInstantiation com ctx genArgs
 
@@ -3718,7 +3718,7 @@ module Util =
                                 )
                             )
 
-                        let fnId = entName + "_" + case.Name |> Identifier.identifier
+                        let fnId = entName + "_" + sanitizeName case.Name |> Identifier.identifier
                         // Don't use return type, TypeScript will infer it and sometimes we want to use
                         // the actual constructor type in case it implements an interface
                         // let returnType = AliasTypeAnnotation(Identifier.identifier(entName + UnionHelpers.UNION_SUFFIX), entParamsInst)
diff --git a/tests/Js/Main/UnionTypeTests.fs b/tests/Js/Main/UnionTypeTests.fs
index 25a58a03a1..534f67666c 100644
--- a/tests/Js/Main/UnionTypeTests.fs
+++ b/tests/Js/Main/UnionTypeTests.fs
@@ -92,6 +92,11 @@ type T8 = T8
 type T9 = T9
 type 'a more = More of 'a
 
+[<RequireQualifiedAccess>]
+type LangCode =
+    | EN
+    | ``pt-Br``
+
 let tests =
   testList "Unions" [
     testCase "Union cases matches with no arguments can be generated" <| fun () ->
@@ -261,4 +266,10 @@ let tests =
                    U9<T1 more, T2 more, T3 more, int, T5 more, T6 more, T7 more, T8 more, T9 more>> = !^42
         x |> equal (U9.Case4 42)
     #endif
-  ]
\ No newline at end of file
+
+    testCase "Verify that union cases can have `-` in their names" <| fun () ->
+        // See https://github.com/fable-compiler/Fable/issues/4071
+        let x = LangCode.``pt-Br``
+
+        equal x LangCode.``pt-Br``
+  ]