Fixes fable-compiler#3847

src/Fable.Cli/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## Unreleased
 
+### Fixed
+
+* [JS/TS] Fixed unwrapping optional arguments (#3847) (by @ncave)
+
 ## 4.19.2 - 2024-06-13
 
 ### Fixed

src/Fable.Transforms/Fable2Babel.fs

@@ -1891,10 +1891,10 @@ module Util =
 
         let args =
             match paramsInfo with
-            | Some i when List.sameLength args i.Parameters ->
-                List.zip args i.Parameters
-                |> List.map (fun (a, i) ->
-                    if i.IsOptional then
+            | Some info when args.Length <= info.Parameters.Length ->
+                List.zipSafe args info.Parameters
+                |> List.map (fun (a, p) ->
+                    if p.IsOptional then
                         unwrapOptionalArg com a |> snd
                     else
                         a

src/Fable.Transforms/Rust/AST/Rust.AST.Adapters.fs

@@ -221,7 +221,7 @@ module fmt =
 type Macros =
     static member assert_eq(actual, expected) = assert (actual = expected)
     static member assert_ne(actual, expected) = assert (actual <> expected)
-    static member unreachable() = failwith "should not happen"
+    static member unreachable() = failwith "unreachable!"
     static member panic() = failwith "panic!"
     static member panic(str: string) = failwith str
 

src/Fable.Transforms/Rust/Fable2Rust.fs

@@ -1615,6 +1615,21 @@ module Util =
         //         let rest = List.rev rest |> List.map (fun e -> com.TransformExpr(ctx, e))
         //         rest @ [Expression.spreadElement(com.TransformExpr(ctx, last))]
         | args ->
+            let optionalArgs =
+                if args.Length < parameters.Length then
+                    parameters
+                    |> List.skip args.Length
+                    |> List.filter (fun p -> p.IsOptional)
+                    |> List.map (fun p ->
+                        match p.Type with
+                        | Fable.Option(t, isStruct) -> Fable.Value(Fable.NewOption(None, t, isStruct), None)
+                        | _ -> failwith "unreachable"
+                    )
+                else
+                    []
+
+            let args = List.append args optionalArgs
+
             let argsWithTypes =
                 if argTypes.Length = args.Length then
                     args |> List.zip argTypes |> List.map (fun (t, a) -> Some t, a)
@@ -2877,7 +2892,7 @@ module Util =
                 |> prepareRefForPatternMatch com ctx fableExpr.Type (tryGetIdentName fableExpr)
 
             mkLetExpr pat expr
-        | _ -> failwith "Should not happen"
+        | _ -> failwith "unreachable"
 
     let transformTest (com: IRustCompiler) ctx range kind (fableExpr: Fable.Expr) : Rust.Expr =
         match kind with
@@ -2923,7 +2938,7 @@ module Util =
                 let thenExpr = mkBoolLitExpr true
                 let elseExpr = mkBoolLitExpr false
                 mkIfThenElseExpr guardExpr thenExpr elseExpr
-            | _ -> failwith "Should not happen"
+            | _ -> failwith "unreachable"
 
     let transformSwitch (com: IRustCompiler) ctx (evalExpr: Fable.Expr) cases defaultCase targets : Rust.Expr =
         let namesForIndex evalType evalName caseIndex = //todo refactor with below

src/Fable.Transforms/Transforms.Util.fs

@@ -1265,11 +1265,9 @@ module AST =
         | None -> args, []
         | Some index when index > args.Length || index > info.Parameters.Length -> args, []
         | Some index ->
-            let args, namedValues = List.splitAt index args
-
-            let namedKeys = List.skip index info.Parameters |> List.truncate namedValues.Length
-
-            args, List.zipSafe namedKeys namedValues
+            let args, namedArgs = List.splitAt index args
+            let namedParams = List.skip index info.Parameters |> List.truncate namedArgs.Length
+            args, List.zipSafe namedParams namedArgs
 
     /// Used to compare arg idents of a lambda wrapping a function call
     let argEquals (argIdents: Ident list) argExprs =

tests/Dart/main.dart

@@ -23,6 +23,7 @@ import './src/SudokuTests.dart' as sudoku;
 import './src/TailCallTests.dart' as tailcall;
 import './src/TimeSpanTests.dart' as timespan;
 import './src/TupleTests.dart' as tuple;
+import './src/TypeTests.dart' as type_;
 import './src/UnionTests.dart' as union;
 
 void main() {
@@ -51,5 +52,6 @@ void main() {
   tailcall.tests();
   timespan.tests();
   tuple.tests();
+  type_.tests();
   union.tests();
 }

tests/Dart/src/Fable.Tests.Dart.fsproj

@@ -33,6 +33,7 @@
     <Compile Include="TailCallTests.fs" />
     <Compile Include="TimeSpanTests.fs" />
     <Compile Include="TupleTests.fs" />
+    <Compile Include="TypeTests.fs" />
     <Compile Include="UnionTests.fs" />
     <Content Include="..\main.dart" />
   </ItemGroup>

tests/Dart/src/RecordTests.fs

@@ -53,6 +53,28 @@ let tests() =
         // x = {| y with Baz = 23 |} |> equal true // Doesn't compile
         x = {| y with Bar = 14 |} |> equal false
 
+    testCase "Anonymous records can have optional fields" <| fun () ->
+        let add (o: {| bar: int option; zas: string option; foo: int option option |}) =
+            let bar = o.bar |> Option.map string |> Option.defaultValue "-"
+            let zas = defaultArg o.zas ""
+            let foo = match o.foo with Some(Some i) -> string i | Some None -> "xx" | None -> "x"
+            bar + zas + foo
+
+        {| bar = Some 3; zas = Some "ooooo"; foo = Some None |} |> add |> equal "3oooooxx"
+        {| bar = Some 22; zas = Some ""; foo = Some(Some 999) |} |> add |> equal "22999"
+        {| bar = None; zas = None; foo = None |} |> add |> equal "-x"
+        {| foo = Some None; bar = None; zas = None |} |> add |> equal "-xx"
+
+    testCase "Anonymous records can have optional function fields" <| fun () ->
+        let add (o: {| bar: (int -> int -> int) option; foo: int -> int -> int |}) =
+            let fn = o.bar
+            let f1 = fn |> Option.map (fun f -> f 6 9) |> Option.defaultValue -3
+            let f2 = match fn with Some f -> f 1 8 | None -> -5
+            o.foo 3 4 + f1 + f2
+
+        {| bar = Some (+); foo = (*) |} |> add |> equal 36
+        {| bar = None; foo = (+) |} |> add |> equal -1
+
     testCase "SRTP works with anonymous records" <| fun () ->
         let ar = [| {|Id=Id"foo"; Name="Sarah"|}; {|Id=Id"bar"; Name="James"|} |]
         replaceById {|Id=Id"ja"; Name="Voll"|} ar |> Seq.head |> fun x -> equal "Sarah" x.Name