[JS/TS/Python] Fix record/value type constructor including static backing fields as parameters

src/Fable.Cli/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* [JS/TS/Python] Fix record/struct types augmented with `static let` or `static member val` generating extra constructor parameters for each static field, causing constructor arguments to be assigned to wrong slots (by @MangelMaxime)
 * [TS] Annotate `System.Collections.Generic.IList<T>` as `MutableArray<T>` (by @MangelMaxime)
 * [JS/TS] Fix `ResizeArray` index getter/setter not throwing `IndexOutOfRangeException` when index is out of bounds (fix #3812) (by @MangelMaxime)
 * [Beam] Fix unused term warning in try/catch when exception variable is not referenced (by @dbrattli)

src/Fable.Compiler/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* [JS/TS/Python] Fix record/struct types augmented with `static let` or `static member val` generating extra constructor parameters for each static field, causing constructor arguments to be assigned to wrong slots (by @MangelMaxime)
 * [TS] Annotate `System.Collections.Generic.IList<T>` as `MutableArray<T>` (by @MangelMaxime)
 * [JS/TS] Fix `ResizeArray` index getter/setter not throwing `IndexOutOfRangeException` when index is out of bounds (fix #3812) (by @MangelMaxime)
 * [Beam] Fix unused term warning in try/catch when exception variable is not referenced (by @dbrattli)

src/Fable.Transforms/Fable2Babel.fs

@@ -176,12 +176,15 @@ module Reflection =
 
         let fields =
             ent.FSharpFields
-            |> List.map (fun fi ->
-                let fieldName = sanitizeMemberName fi.Name |> Expression.stringLiteral
+            |> List.choose (fun fi ->
+                if fi.IsStatic then
+                    None
+                else
+                    let fieldName = sanitizeMemberName fi.Name |> Expression.stringLiteral
 
-                let typeInfo = transformTypeInfoFor Reflection com ctx r genMap fi.FieldType
+                    let typeInfo = transformTypeInfoFor Reflection com ctx r genMap fi.FieldType
 
-                Expression.arrayExpression ([| fieldName; typeInfo |])
+                    Some(Expression.arrayExpression ([| fieldName; typeInfo |]))
             )
             |> List.toArray
 
@@ -3410,10 +3413,13 @@ but thanks to the optimisation done below we get
 
     let getEntityFieldsAsIdents (ent: Fable.Entity) =
         ent.FSharpFields
-        |> List.map (fun field ->
-            let name = sanitizeName field.Name
-            let typ = field.FieldType
-            { makeTypedIdent typ name with IsMutable = field.IsMutable }
+        |> List.choose (fun field ->
+            if field.IsStatic then
+                None
+            else
+                let name = sanitizeName field.Name
+                let typ = field.FieldType
+                Some { makeTypedIdent typ name with IsMutable = field.IsMutable }
         )
 
     let declareClassWithParams
@@ -3997,6 +4003,7 @@ but thanks to the optimisation done below we get
                         yield callSuperAsStatement []
                     yield!
                         ent.FSharpFields
+                        |> List.filter (fun field -> not field.IsStatic)
                         |> List.mapi (fun i field ->
                             let left = get None thisExpr field.Name
 

src/Fable.Transforms/FableTransforms.fs

@@ -745,7 +745,11 @@ module private Transforms =
             Emit({ emitInfo with CallInfo = { callInfo with Args = args } }, t, r)
         // Uncurry also values in setters or new record/union/tuple
         | Value(NewRecord(args, ent, genArgs), r) ->
-            let args = com.GetEntity(ent).FSharpFields |> uncurryConsArgs args
+            let args =
+                com.GetEntity(ent).FSharpFields
+                |> Seq.filter (fun f -> not f.IsStatic)
+                |> uncurryConsArgs args
+
             Value(NewRecord(args, ent, genArgs), r)
         | Value(NewAnonymousRecord(args, fieldNames, genArgs, isStruct), r) ->
             let args = uncurryArgs com false genArgs args

src/Fable.Transforms/Python/Fable2Python.Reflection.fs

@@ -32,16 +32,19 @@ let private transformRecordReflectionInfo com ctx r (ent: Fable.Entity) generics
 
     let fields, stmts =
         ent.FSharpFields
-        |> Seq.map (fun fi ->
-            let typeInfo, stmts = transformTypeInfo com ctx r genMap fi.FieldType
+        |> Seq.choose (fun fi ->
+            if fi.IsStatic then
+                None
+            else
+                let typeInfo, stmts = transformTypeInfo com ctx r genMap fi.FieldType
 
-            let name =
-                if Util.shouldUseRecordFieldNaming ent then
-                    fi.Name |> Naming.toRecordFieldSnakeCase |> Helpers.clean
-                else
-                    fi.Name |> Naming.toSnakeCase |> Helpers.clean
+                let name =
+                    if Util.shouldUseRecordFieldNaming ent then
+                        fi.Name |> Naming.toRecordFieldSnakeCase |> Helpers.clean
+                    else
+                        fi.Name |> Naming.toSnakeCase |> Helpers.clean
 
-            Expression.tuple [ Expression.stringConstant name; typeInfo ], stmts
+                Some(Expression.tuple [ Expression.stringConstant name; typeInfo ], stmts)
         )
         |> Seq.toList
         |> Helpers.unzipArgs

src/Fable.Transforms/Python/Fable2Python.Transforms.fs

@@ -3197,14 +3197,17 @@ let getEntityFieldsAsIdents (com: IPythonCompiler) (ent: Fable.Entity) =
             Naming.toPythonNaming
 
     ent.FSharpFields
-    |> Seq.map (fun field ->
-        let name =
-            (entityNamingConvention field.Name, Naming.NoMemberPart)
-            ||> Naming.sanitizeIdent (fun _ -> false)
+    |> Seq.choose (fun field ->
+        if field.IsStatic then
+            None
+        else
+            let name =
+                (entityNamingConvention field.Name, Naming.NoMemberPart)
+                ||> Naming.sanitizeIdent (fun _ -> false)
 
-        let typ = field.FieldType
+            let typ = field.FieldType
 
-        { makeTypedIdent typ name with IsMutable = field.IsMutable }
+            Some { makeTypedIdent typ name with IsMutable = field.IsMutable }
     )
     |> Seq.toArray
 
@@ -3248,6 +3251,7 @@ let declareDataClassType
     // lambda types in the type annotations to match.
     let props =
         ent.FSharpFields
+        |> List.filter (fun field -> not field.IsStatic)
         |> List.mapi (fun i field ->
             // Get the argument name from consArgs (preserves the Python naming convention)
             let argName =
@@ -3343,8 +3347,33 @@ let declareDataClassType
             returns = Expression.name "int"
         )
 
+    // Generate ClassVar annotations for static fields so that Pyright recognizes
+    // the class-level attributes assigned by the static constructor (_cctor).
+    // With slots=True, unannotated class attributes are not allowed.
+    let staticFieldAnnotations =
+        ent.FSharpFields
+        |> List.choose (fun field ->
+            if
+                field.IsStatic
+                && not (field.Name.StartsWith("init@", System.StringComparison.Ordinal))
+            then
+                let fieldName = field.Name.TrimEnd('@') |> Naming.toPythonNaming
+                let ta, _ = Annotation.typeAnnotation com ctx None field.FieldType
+                let classVar = com.GetImportExpr(ctx, "typing", "ClassVar")
+                let classVarAnnotation = Expression.subscript (classVar, ta)
+                Some(Statement.annAssign (Expression.name fieldName, annotation = classVarAnnotation))
+            else
+                None
+        )
+
     let classBody =
-        let body = [ yield! props; yield! classMembers; yield hashMethod ]
+        let body =
+            [
+                yield! staticFieldAnnotations
+                yield! props
+                yield! classMembers
+                yield hashMethod
+            ]
 
         match body with
         | [] -> [ Statement.ellipsis ]
@@ -4142,6 +4171,7 @@ let transformClassWithCompilerGeneratedConstructor
             if classAttributes.Style = ClassStyle.Attributes then
                 yield!
                     ent.FSharpFields
+                    |> List.filter (fun field -> not field.IsStatic)
                     |> List.collect (fun field ->
                         let fieldName = field.Name |> Naming.toPropertyNaming
                         let left = get com ctx None thisExpr fieldName false
@@ -4155,6 +4185,7 @@ let transformClassWithCompilerGeneratedConstructor
             else
                 yield!
                     ent.FSharpFields
+                    |> List.filter (fun field -> not field.IsStatic)
                     |> List.collecti (fun i field ->
                         let fieldName =
                             if shouldUseRecordFieldNaming ent then

tests/Js/Main/RecordTypeTests.fs

@@ -45,6 +45,17 @@ type Time =
 type CarInterior = { Seats: int }
 type Car = { Interior: CarInterior }
 
+// Issue #3923 - static let on a record shifts constructor arg indices
+type RecordWithStaticLet =
+    { id: int }
+    static let _a = 2
+    static member a = _a
+
+// Issue #4091 - static member val on a record causes shared mutable state
+type RecordWithStaticMemberVal =
+    { xs: ResizeArray<int> }
+    static member val empty = { xs = ResizeArray() }
+
 let tests =
   testList "RecordTypes" [
 
@@ -160,4 +171,18 @@ let tests =
             {| car with Interior.Seats = 5 |}
         equal 5 car2.Interior.Seats
 
+    // Issue #3923
+    testCase "Record with static let has correct constructor" <| fun () ->
+        let x = { id = 1 }
+        equal 1 x.id
+        equal 2 RecordWithStaticLet.a
+
+    // Issue #4091
+    testCase "Record with static member val does not share state across instances" <| fun () ->
+        let a = RecordWithStaticMemberVal.empty
+        let b = RecordWithStaticMemberVal.empty
+        a.xs.Add 1
+        equal 1 a.xs.Count
+        equal 1 b.xs.Count
+
   ]

tests/Python/TestRecordType.fs

@@ -42,6 +42,17 @@ type Time =
 type CarInterior = { Seats: int }
 type Car = { Interior: CarInterior }
 
+// Issue #3923 - static let on a record shifts constructor arg indices
+type RecordWithStaticLet =
+    { id: int }
+    static let _a = 2
+    static member a = _a
+
+// Issue #4091 - static member val on a record causes shared mutable state
+type RecordWithStaticMemberVal =
+    { xs: ResizeArray<int> }
+    static member val empty = { xs = ResizeArray() }
+
 type RecordA =
     { OptionalField : string option }
 
@@ -199,4 +210,20 @@ type RecordWithProperty =
 [<Fact>]
 let ``test Record property access uses correct naming`` () =
     let x = { items = ["Hello"; "World"] }
-    equal "Hello - World" x.fullName
+    equal "Hello - World" x.fullName
+
+// Issue #3923
+[<Fact>]
+let ``test Record with static let has correct constructor`` () =
+    let x = { id = 1 }
+    equal 1 x.id
+    equal 2 RecordWithStaticLet.a
+
+// Issue #4091
+[<Fact>]
+let ``test Record with static member val does not share state across instances`` () =
+    let a = RecordWithStaticMemberVal.empty
+    let b = RecordWithStaticMemberVal.empty
+    a.xs.Add 1
+    equal 1 a.xs.Count
+    equal 1 b.xs.Count