fix: drop allowAccessToPrivateRepresentation arg from reflection calls

src/Fable.Transforms/Python/Replacements.fs

@@ -3967,7 +3967,8 @@ let fsharpType com methName (r: SourceLocation option) t (i: CallInfo) (args: Ex
         |> Some
     // Prevent name clash with FSharpValue.GetRecordFields
     | "GetRecordFields" ->
-        Helper.LibCall(com, "Reflection", "get_record_elements", t, args, i.SignatureArgTypes, ?loc = r)
+        // Drop the trailing `allowAccessToPrivateRepresentation` flag (no meaning in Python)
+        Helper.LibCall(com, "Reflection", "get_record_elements", t, List.truncate 1 args, i.SignatureArgTypes, ?loc = r)
         |> Some
     | "GetUnionCases"
     | "GetTupleElements"
@@ -3992,6 +3993,16 @@ let fsharpValue com methName (r: SourceLocation option) t (i: CallInfo) (args: E
     | "MakeUnion"
     | "MakeRecord"
     | "MakeTuple" ->
+        // Drop the trailing `allowAccessToPrivateRepresentation` flag, a .NET-only
+        // concept the runtime helpers don't accept.
+        let args =
+            match methName with
+            | "GetRecordFields" -> List.truncate 1 args
+            | "GetUnionFields"
+            | "MakeUnion"
+            | "MakeRecord" -> List.truncate 2 args
+            | _ -> args
+
         Helper.LibCall(com, "Reflection", Naming.lowerFirst methName, t, args, i.SignatureArgTypes, ?loc = r)
         |> Some
     | "GetExceptionFields" -> None // TODO!!!

src/Fable.Transforms/Replacements.fs

@@ -4154,7 +4154,8 @@ let fsharpType com (ctx: Context) methName (r: SourceLocation option) t (i: Call
         |> Some
     // Prevent name clash with FSharpValue.GetRecordFields
     | "GetRecordFields" ->
-        Helper.LibCall(com, "Reflection", "getRecordElements", t, args, i.SignatureArgTypes, ?loc = r)
+        // Drop the trailing `allowAccessToPrivateRepresentation` flag (no meaning in JS/TS)
+        Helper.LibCall(com, "Reflection", "getRecordElements", t, List.truncate 1 args, i.SignatureArgTypes, ?loc = r)
         |> Some
     | "GetUnionCases"
     | "GetTupleElements"
@@ -4185,6 +4186,16 @@ let fsharpValue com methName (r: SourceLocation option) t (i: CallInfo) (args: E
     | "MakeUnion"
     | "MakeRecord"
     | "MakeTuple" ->
+        // Drop the trailing `allowAccessToPrivateRepresentation` flag, a .NET-only
+        // concept the runtime helpers don't accept.
+        let args =
+            match methName with
+            | "GetRecordFields" -> List.truncate 1 args
+            | "GetUnionFields"
+            | "MakeUnion"
+            | "MakeRecord" -> List.truncate 2 args
+            | _ -> args
+
         Helper.LibCall(com, "Reflection", Naming.lowerFirst methName, t, args, i.SignatureArgTypes, ?loc = r)
         |> Some
     | "GetExceptionFields" -> None // TODO!!!

tests/Js/Main/ReflectionTests.fs

@@ -381,6 +381,24 @@ let reflectionTests = [
     let all = isRecord && matchRecordFields && matchIndividualRecordFields && canMakeSameRecord
     all |> equal true
 
+  testCase "Reflection functions accept allowAccessToPrivateRepresentation" <| fun () ->
+    let recordType = typeof<TestRecord>
+    let record = { String = "a"; Int = 1 }
+
+    FSharpType.GetRecordFields(recordType, allowAccessToPrivateRepresentation = true).Length |> equal 2
+
+    let values = FSharpValue.GetRecordFields(record, allowAccessToPrivateRepresentation = true)
+    let rebuilt =
+        FSharpValue.MakeRecord(recordType, values, allowAccessToPrivateRepresentation = true) :?> TestRecord
+    rebuilt |> equal record
+
+    let unionType = typeof<TestUnion>
+    let intCase = FSharpType.GetUnionCases(unionType).[1]
+    let u = FSharpValue.MakeUnion(intCase, [| box 5 |], allowAccessToPrivateRepresentation = true) :?> TestUnion
+    let info, fields = FSharpValue.GetUnionFields(u, unionType, allowAccessToPrivateRepresentation = true)
+    info.Name |> equal "IntCase"
+    fields.[0] |> equal (box 5)
+
   testCase "PropertyInfo.GetValue works" <| fun () ->
     let value: obj = { Firstname = "Maxime"; Age = 12 } :> obj
 

tests/Python/TestReflection.fs

@@ -218,6 +218,25 @@ let ``test Reflection Array`` () =
     typeof<bool> = elType |> equal false
     liType.GetElementType() |> equal null
 
+[<Fact>]
+let ``test reflection functions accept allowAccessToPrivateRepresentation`` () =
+    let recordType = typeof<MyRecord>
+    let record = { String = "a"; Int = 1 }
+
+    FSharpType.GetRecordFields(recordType, allowAccessToPrivateRepresentation = true).Length |> equal 2
+
+    let values = FSharpValue.GetRecordFields(record, allowAccessToPrivateRepresentation = true)
+    let rebuilt =
+        FSharpValue.MakeRecord(recordType, values, allowAccessToPrivateRepresentation = true) :?> MyRecord
+    rebuilt |> equal record
+
+    let unionType = typeof<MyUnion>
+    let intCase = FSharpType.GetUnionCases(unionType).[1]
+    let u = FSharpValue.MakeUnion(intCase, [| box 5 |], allowAccessToPrivateRepresentation = true) :?> MyUnion
+    let info, fields = FSharpValue.GetUnionFields(u, unionType, allowAccessToPrivateRepresentation = true)
+    info.Name |> equal "IntCase"
+    fields.[0] |> equal (box 5)
+
 #if FABLE_COMPILER
 [<Fact>]
 let ``test FSharp.Reflection Record`` () =