From 7a9db876b02b23e5379d1e549e9a6924c3094df9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=A1=D0=BB=D0=B0=D0=B2=D0=B0=20=D0=A3=D0=BA=D1=80=D0=B0?=
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 <777696+ncave@users.noreply.github.com>
Date: Thu, 13 Jun 2024 11:52:41 -0700
Subject: [PATCH] fix: missing `type` property for `TypeScriptTaggedUnion`
 cases with a single argument (#3844)

Fix #3837
---
 src/Fable.Cli/CHANGELOG.md                |  1 +
 src/Fable.Transforms/FSharp2Fable.Util.fs |  5 +++--
 src/Fable.Transforms/FSharp2Fable.fs      | 20 ++++++++++----------
 src/Fable.Transforms/Fable2Babel.fs       | 12 ++++++------
 4 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/src/Fable.Cli/CHANGELOG.md b/src/Fable.Cli/CHANGELOG.md
index 07b3886d91..fa7162e215 100644
--- a/src/Fable.Cli/CHANGELOG.md
+++ b/src/Fable.Cli/CHANGELOG.md
@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * [All] Ignore testers for erased union cases (#3658) (by @ncave)
 * [All] Fixed Fable compiler hanging on some errors (#3842) (by @ncave)
 * [JS/TS] Fixed DateTime.MinValue, DateTime.MaxValue (#3836) (by @ncave)
+* [JS/TS] Fixed missing field using TypeScriptTaggedUnion (#3837) (by @ncave)
 
 ## 4.19.0 - 2024-06-10
 
diff --git a/src/Fable.Transforms/FSharp2Fable.Util.fs b/src/Fable.Transforms/FSharp2Fable.Util.fs
index 1ec73744d8..41bf908e54 100644
--- a/src/Fable.Transforms/FSharp2Fable.Util.fs
+++ b/src/Fable.Transforms/FSharp2Fable.Util.fs
@@ -134,8 +134,9 @@ type FsUnionCase(uci: FSharpUnionCase) =
             | _ -> None
         )
 
-    static member HasNamedFields(uci: FSharpUnionCase) =
-        not (uci.Fields.Count = 1 && uci.Fields[0].Name = "Item")
+    // static member HasNamedFields(uci: FSharpUnionCase) =
+    //     not (uci.Fields.Count = 1 && uci.Fields[0].Name = "Item")
+    //     true
 
     interface Fable.UnionCase with
         member _.Name = uci.Name
diff --git a/src/Fable.Transforms/FSharp2Fable.fs b/src/Fable.Transforms/FSharp2Fable.fs
index 48c23cc8e6..48b63417b4 100644
--- a/src/Fable.Transforms/FSharp2Fable.fs
+++ b/src/Fable.Transforms/FSharp2Fable.fs
@@ -74,7 +74,7 @@ let private transformNewUnion com ctx r fsType (unionCase: FSharpUnionCase) (arg
 
     | TypeScriptTaggedUnion(_, _, tagName, rule) ->
         match argExprs with
-        | [ argExpr ] when not (FsUnionCase.HasNamedFields unionCase) -> argExpr
+        // | [ argExpr ] when not (FsUnionCase.HasNamedFields unionCase) -> argExpr
         | _ ->
             let isCompiledValue, tagExpr =
                 match FsUnionCase.CompiledValue unionCase with
@@ -1179,16 +1179,16 @@ let private transformExpr (com: IFableCompiler) (ctx: Context) appliedGenArgs fs
 
                     return Fable.Get(unionExpr, Fable.TupleIndex index, fieldType, r)
             | TypeScriptTaggedUnion _ ->
-                if FsUnionCase.HasNamedFields unionCase then
-                    let kind =
-                        Fable.FieldInfo.Create(
-                            FsField.FSharpFieldName field,
-                            fieldType = makeType Map.empty field.FieldType
-                        )
+                // if not (FsUnionCase.HasNamedFields unionCase) then
+                //     return unionExpr
+                // else
+                let kind =
+                    Fable.FieldInfo.Create(
+                        FsField.FSharpFieldName field,
+                        fieldType = makeType Map.empty field.FieldType
+                    )
 
-                    return Fable.Get(unionExpr, kind, fieldType, r)
-                else
-                    return unionExpr
+                return Fable.Get(unionExpr, kind, fieldType, r)
             | StringEnum _ ->
                 return
                     "StringEnum types cannot have fields"
diff --git a/src/Fable.Transforms/Fable2Babel.fs b/src/Fable.Transforms/Fable2Babel.fs
index b587877e9a..a2766ff1ef 100644
--- a/src/Fable.Transforms/Fable2Babel.fs
+++ b/src/Fable.Transforms/Fable2Babel.fs
@@ -852,12 +852,12 @@ module Annotation =
                 AbstractMember.abstractProperty (prop, tagType, isComputed = isComputed)
 
             match uci.UnionCaseFields with
-            | [ field ] when field.Name = "Item" ->
-                IntersectionTypeAnnotation
-                    [|
-                        field.FieldType |> resolveInlineType genArgs |> makeFieldAnnotation com ctx
-                        ObjectTypeAnnotation [| tagMember |]
-                    |]
+            // | [ field ] when field.Name = "Item" ->
+            //     IntersectionTypeAnnotation
+            //         [|
+            //             field.FieldType |> resolveInlineType genArgs |> makeFieldAnnotation com ctx
+            //             ObjectTypeAnnotation [| tagMember |]
+            //         |]
             | fields ->
                 let names, types =
                     fields |> List.map (fun fi -> fi.Name, fi.FieldType) |> List.unzip