Add Core standard library support for genType (#6019)

* Add `Core` standard library support for `genType`

See https://forum.rescript-lang.org/t/difficulty-with-shims-and-undefined-t-and-null-t/4240

* genType: treat Dict.t type as built-in.

* Support `Promise.t`.

* Support `Date.t`.

* Support BigInt

* Support RegExp.

* Support Map and WeakMap

* Support Set and WeakSet.

* Update CHANGELOG.md

* Clean up unused Record and RecordC.

* genType: treat option<t> as t | undefined

This produces strictly fewer conversion functions, as it does not need to transform `null` to `undefined`.

* Remove special treatment of `{x:option<t>}` as optional field.

This is a breaking changes, but aligns more closely with TS.

The two TS types:

```ts
type t1 = { x?: string };

type t2 = { x: (undefined | string) };
```

now correspond to the ReScript types:
```res
@genType
type t1 = {x?: string}

@genType
type t2 = {x: Js.undefined<string>}
```

The special treatment of fields of option type comes from a time where records with optional fields did not exist.

* Add examples of what can and cannot be used in bindings to functions.

* Update CHANGELOG.md

Author: cristianoc

CHANGELOG.md

@@ -26,6 +26,7 @@ subset of the arguments, and return a curried type with the remaining ones https
 - Add support for toplevel `await` https://github.com/rescript-lang/rescript-compiler/pull/5940
 - Support optional named arguments without a final unit in uncurried functions https://github.com/rescript-lang/rescript-compiler/pull/5907
 - Add experimental suppport for directives. An annotation such as `@@directive("use client;")` emits `use client;` verbatim before imports https://github.com/rescript-lang/rescript-compiler/pull/5998
+- `genType`: add `Core` standard library support for the following builtin types: `Null.t`, `Nullable.t`, `Undefined.t`, `Dict.t<_>`, `Promise.t<_>`, `Date.t`, `BigInt.t`, `RegExp.t`, `Map.t<_, _>`, `WeakMap.t<_, _>`, `Set<_>`, `WeakSet<_>` https://github.com/rescript-lang/rescript-compiler/pull/6019
 
 #### :boom: Breaking Change
 
@@ -39,6 +40,9 @@ subset of the arguments, and return a curried type with the remaining ones https
 Also, `(. int) => string => bool` is not equivalen to `(. int, string) => bool` anymore.
 These are only breaking changes for unformatted code.
 - Exponentiation operator `**` is now right-associative. `2. ** 3. ** 2.` now compile to `Math.pow(2, Math.pow(3, 2))` and not anymore `Math.pow(Math.pow(2, 3), 2)`. Parentheses can be used to change precedence.
+- `genType`: streamline the treatment of optionals as undefined https://github.com/rescript-lang/rescript-compiler/pull/6022
+  - Represent `option<t>` as `undefined | t` instead of `null | undefined | t`. This is more permissive when importing functions taking optional values (allows to use option types), but stricter when e.g. exporting ReScript functions taking arguments of option type. Fallback: use `Js.undefined<_>` instead.
+  - Represent `{x:option<string>}` as `{x:(undefined | string)}` instead of `{x?: string}`. This is more in line with TS's behaviour. Fallback: use `{x?:string}`.
 
 #### :bug: Bug Fix
 

jscomp/gentype/Converter.ml

@@ -5,11 +5,9 @@ type t =
   | CircularC of string * t
   | FunctionC of functionC
   | IdentC
-  | NullableC of t
   | ObjectC of fieldsC
   | OptionC of t
   | PromiseC of t
-  | RecordC of fieldsC
   | TupleC of t list
   | VariantC of variantC
 
@@ -68,8 +66,7 @@ let rec toString converter =
       |> String.concat ", ")
     ^ " -> " ^ toString retConverter ^ ")"
   | IdentC -> "id"
-  | NullableC c -> "nullable(" ^ toString c ^ ")"
-  | ObjectC fieldsC | RecordC fieldsC ->
+  | ObjectC fieldsC ->
     let dot =
       match converter with
       | ObjectC _ -> ". "
@@ -120,6 +117,7 @@ let typeGetConverterNormalized ~config ~inline ~lookupId ~typeNameIsInterface
     | Array (t, mutable_) ->
       let tConverter, tNormalized = t |> visit ~visited in
       (ArrayC tConverter, Array (tNormalized, mutable_))
+    | Dict _ -> (IdentC, normalized_)
     | Function
         ({argTypes; componentName; retType; typeVars; uncurried} as function_)
       ->
@@ -189,10 +187,10 @@ let typeGetConverterNormalized ~config ~inline ~lookupId ~typeNameIsInterface
           else (IdentC, normalized_))
     | Null t ->
       let tConverter, tNormalized = t |> visit ~visited in
-      (NullableC tConverter, Null tNormalized)
+      (OptionC tConverter, Null tNormalized)
     | Nullable t ->
       let tConverter, tNormalized = t |> visit ~visited in
-      (NullableC tConverter, Nullable tNormalized)
+      (OptionC tConverter, Nullable tNormalized)
     | Object (closedFlag, fields) ->
       let fieldsConverted =
         fields
@@ -220,26 +218,6 @@ let typeGetConverterNormalized ~config ~inline ~lookupId ~typeNameIsInterface
     | Promise t ->
       let tConverter, tNormalized = t |> visit ~visited in
       (PromiseC tConverter, Promise tNormalized)
-    | Record fields ->
-      let fieldsConverted =
-        fields
-        |> List.map (fun ({type_} as field) -> (field, type_ |> visit ~visited))
-      in
-      ( RecordC
-          (fieldsConverted
-          |> List.map (fun ({nameJS; nameRE; optional}, (converter, _)) ->
-                 {
-                   lblJS = nameJS;
-                   lblRE = nameRE;
-                   c =
-                     (match optional = Mandatory with
-                     | true -> converter
-                     | false -> OptionC converter);
-                 })),
-        Record
-          (fieldsConverted
-          |> List.map (fun (field, (_, tNormalized)) ->
-                 {field with type_ = tNormalized})) )
     | Tuple innerTypes ->
       let innerConversions, normalizedList =
         innerTypes |> List.map (visit ~visited) |> List.split
@@ -379,7 +357,6 @@ let rec converterIsIdentity ~config ~toJS converter =
                 argConverter |> converterIsIdentity ~config ~toJS:(not toJS)
               | GroupConverter _ -> false)
   | IdentC -> true
-  | NullableC c -> c |> converterIsIdentity ~config ~toJS
   | ObjectC fieldsC ->
     fieldsC
     |> List.for_all (fun {lblJS; lblRE; c} ->
@@ -388,9 +365,8 @@ let rec converterIsIdentity ~config ~toJS converter =
            match c with
            | OptionC c1 -> c1 |> converterIsIdentity ~config ~toJS
            | _ -> c |> converterIsIdentity ~config ~toJS)
-  | OptionC c -> if toJS then c |> converterIsIdentity ~config ~toJS else false
+  | OptionC c -> c |> converterIsIdentity ~config ~toJS
   | PromiseC c -> c |> converterIsIdentity ~config ~toJS
-  | RecordC _ -> false
   | TupleC innerTypesC ->
     innerTypesC |> List.for_all (converterIsIdentity ~config ~toJS)
   | VariantC {withPayloads; useVariantTables} ->
@@ -518,13 +494,6 @@ let rec apply ~config ~converter ~indent ~nameGen ~toJS ~variantTables value =
     EmitText.funDef ~bodyArgs ~functionName:componentName ~funParams ~indent
       ~mkBody ~typeVars
   | IdentC -> value
-  | NullableC c ->
-    EmitText.parens
-      [
-        value ^ " == null ? " ^ value ^ " : "
-        ^ (value
-          |> apply ~config ~converter:c ~indent ~nameGen ~toJS ~variantTables);
-      ]
   | ObjectC fieldsC ->
     let simplifyFieldConverted fieldConverter =
       match fieldConverter with
@@ -553,62 +522,19 @@ let rec apply ~config ~converter ~indent ~nameGen ~toJS ~variantTables value =
     in
     "{" ^ fieldValues ^ "}"
   | OptionC c ->
-    if toJS then
-      EmitText.parens
-        [
-          value ^ " == null ? " ^ value ^ " : "
-          ^ (value
-            |> apply ~config ~converter:c ~indent ~nameGen ~toJS ~variantTables
-            );
-        ]
-    else
-      EmitText.parens
-        [
-          value ^ " == null ? undefined : "
-          ^ (value
-            |> apply ~config ~converter:c ~indent ~nameGen ~toJS ~variantTables
-            );
-        ]
+    EmitText.parens
+      [
+        value ^ " == null ? " ^ value ^ " : "
+        ^ (value
+          |> apply ~config ~converter:c ~indent ~nameGen ~toJS ~variantTables);
+      ]
   | PromiseC c ->
     let x = "$promise" |> EmitText.name ~nameGen in
     value ^ ".then(function _element("
     ^ (x |> EmitType.ofTypeAny ~config)
     ^ ") { return "
     ^ (x |> apply ~config ~converter:c ~indent ~nameGen ~toJS ~variantTables)
     ^ "})"
-  | RecordC fieldsC ->
-    let simplifyFieldConverted fieldConverter =
-      match fieldConverter with
-      | OptionC converter1 when converter1 |> converterIsIdentity ~config ~toJS
-        ->
-        IdentC
-      | _ -> fieldConverter
-    in
-    if toJS then
-      let fieldValues =
-        fieldsC
-        |> List.mapi (fun index {lblJS; c = fieldConverter} ->
-               lblJS ^ ":"
-               ^ (value
-                 |> EmitText.arrayAccess ~index
-                 |> apply ~config
-                      ~converter:(fieldConverter |> simplifyFieldConverted)
-                      ~indent ~nameGen ~toJS ~variantTables))
-        |> String.concat ", "
-      in
-      "{" ^ fieldValues ^ "}"
-    else
-      let fieldValues =
-        fieldsC
-        |> List.map (fun {lblJS; c = fieldConverter} ->
-               value
-               |> EmitText.fieldAccess ~label:lblJS
-               |> apply ~config
-                    ~converter:(fieldConverter |> simplifyFieldConverted)
-                    ~indent ~nameGen ~toJS ~variantTables)
-        |> String.concat ", "
-      in
-      "[" ^ fieldValues ^ "]"
   | TupleC innerTypesC ->
     "["
     ^ (innerTypesC

jscomp/gentype/EmitJs.ml

@@ -101,7 +101,7 @@ let typeNameIsInterface ~(exportTypeMap : CodeItem.exportTypeMap)
     ~(exportTypeMapFromOtherFiles : CodeItem.exportTypeMap) typeName =
   let typeIsInterface type_ =
     match type_ with
-    | Object _ | Record _ -> true
+    | Object _ -> true
     | _ -> false
   in
   match exportTypeMap |> StringMap.find typeName with
@@ -620,11 +620,11 @@ let propagateAnnotationToSubTypes ~codeItems (typeMap : CodeItem.exportTypeMap)
             type1 |> visit
           | exception Not_found ->
             annotatedSet := !annotatedSet |> StringSet.add typeName)
-      | Array (t, _) -> t |> visit
+      | Array (t, _) | Dict t -> t |> visit
       | Function {argTypes; retType} ->
         argTypes |> List.iter (fun {aType} -> visit aType);
         retType |> visit
-      | GroupOfLabeledArgs fields | Object (_, fields) | Record fields ->
+      | GroupOfLabeledArgs fields | Object (_, fields) ->
         fields |> List.iter (fun {type_} -> type_ |> visit)
       | Option t | Null t | Nullable t | Promise t -> t |> visit
       | Tuple innerTypes -> innerTypes |> List.iter visit

jscomp/gentype/EmitType.ml

@@ -95,6 +95,10 @@ let rec renderType ~(config : Config.t) ?(indent = None) ~typeNameIsInterface
       arrayName ^ "<"
       ^ (t |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
       ^ ">"
+  | Dict type_ ->
+    "{[id: string]: "
+    ^ (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
+    ^ "}"
   | Function
       {argTypes = [{aType = Object (closedFlag, fields)}]; retType; typeVars}
     when retType |> isTypeFunctionComponent ~fields ->
@@ -116,7 +120,7 @@ let rec renderType ~(config : Config.t) ?(indent = None) ~typeNameIsInterface
   | Function {argTypes; retType; typeVars} ->
     renderFunType ~config ~indent ~inFunType ~typeNameIsInterface ~typeVars
       argTypes retType
-  | GroupOfLabeledArgs fields | Object (_, fields) | Record fields ->
+  | GroupOfLabeledArgs fields | Object (_, fields) ->
     let indent1 = fields |> Indent.heuristicFields ~indent in
     fields
     |> renderFields ~config ~indent:indent1 ~inFunType ~typeNameIsInterface
@@ -136,7 +140,7 @@ let rec renderType ~(config : Config.t) ?(indent = None) ~typeNameIsInterface
     "(null | "
     ^ (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
     ^ ")"
-  | Nullable type_ | Option type_ ->
+  | Nullable type_ ->
     let useParens x =
       match type_ with
       | Function _ | Variant _ -> EmitText.parens [x]
@@ -146,6 +150,16 @@ let rec renderType ~(config : Config.t) ?(indent = None) ~typeNameIsInterface
     ^ useParens
         (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
     ^ ")"
+  | Option type_ ->
+    let useParens x =
+      match type_ with
+      | Function _ | Variant _ -> EmitText.parens [x]
+      | _ -> x
+    in
+    "(undefined | "
+    ^ useParens
+        (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)
+    ^ ")"
   | Promise type_ ->
     "Promise" ^ "<"
     ^ (type_ |> renderType ~config ~indent ~typeNameIsInterface ~inFunType)

jscomp/gentype/GenTypeCommon.ml

@@ -59,6 +59,7 @@ type closedFlag = Open | Closed
 
 type type_ =
   | Array of type_ * mutable_
+  | Dict of type_
   | Function of function_
   | GroupOfLabeledArgs of fields
   | Ident of ident
@@ -67,7 +68,6 @@ type type_ =
   | Object of closedFlag * fields
   | Option of type_
   | Promise of type_
-  | Record of fields
   | Tuple of type_ list
   | TypeVar of string
   | Variant of variant
@@ -108,6 +108,7 @@ and payload = {case: case; inlineRecord: bool; numArgs: int; t: type_}
 let typeIsObject type_ =
   match type_ with
   | Array _ -> true
+  | Dict _ -> true
   | Function _ -> false
   | GroupOfLabeledArgs _ -> false
   | Ident _ -> false
@@ -116,7 +117,6 @@ let typeIsObject type_ =
   | Object _ -> true
   | Option _ -> false
   | Promise _ -> true
-  | Record _ -> true
   | Tuple _ -> true
   | TypeVar _ -> false
   | Variant _ -> false
@@ -210,11 +210,17 @@ let sanitizeTypeName name =
        | '\'' -> '_'
        | c -> c)
 let unknown = ident "unknown"
+let bigintT = ident "BigInt"
 let booleanT = ident "boolean"
 let dateT = ident "Date"
+let mapT (x,y) = ident ~typeArgs:[x;y] "Map"
 let numberT = ident "number"
+let regexpT = ident "RegExp"
+let setT (x) = ident ~typeArgs:[x] "Set"
 let stringT = ident "string"
 let unitT = ident "void"
+let weakmapT (x,y) = ident ~typeArgs:[x;y] "WeakMap"
+let weaksetT (x) = ident ~typeArgs:[x] "WeakSet"
 let int64T = Tuple [numberT; numberT]
 
 module NodeFilename = struct

jscomp/gentype/TranslateSignatureFromTypes.ml

@@ -12,8 +12,9 @@ let translateTypeDeclarationFromTypes ~config ~outputFileRelative ~resolver
     Log_.item "Translate Types.type_declaration %s\n" typeName;
   let declarationKind =
     match type_kind with
-    | Type_record (labelDeclarations, _) ->
-      TranslateTypeDeclarations.RecordDeclarationFromTypes labelDeclarations
+    | Type_record (labelDeclarations, recordRepresentation) ->
+      TranslateTypeDeclarations.RecordDeclarationFromTypes
+        (labelDeclarations, recordRepresentation)
     | Type_variant constructorDeclarations
       when not
              (TranslateTypeDeclarations.hasSomeGADTLeaf constructorDeclarations)

jscomp/gentype/TranslateTypeDeclarations.ml

@@ -1,7 +1,8 @@
 open GenTypeCommon
 
 type declarationKind =
-  | RecordDeclarationFromTypes of Types.label_declaration list
+  | RecordDeclarationFromTypes of
+      Types.label_declaration list * Types.record_representation
   | GeneralDeclaration of Typedtree.core_type option
   | GeneralDeclarationFromTypes of Types.type_expr option
       (** As the above, but from Types not Typedtree *)
@@ -78,7 +79,12 @@ let traslateDeclarationKind ~config ~loc ~outputFileRelative ~resolver
     in
     {CodeItem.importTypes; exportFromTypeDeclaration}
   in
-  let translateLabelDeclarations labelDeclarations =
+  let translateLabelDeclarations ~recordRepresentation labelDeclarations =
+    let isOptional l =
+      match recordRepresentation with
+      | Types.Record_optional_labels lbls -> List.mem l lbls
+      | _ -> false
+    in
     let fieldTranslations =
       labelDeclarations
       |> List.map (fun {Types.ld_id; ld_mutable; ld_type; ld_attributes} ->
@@ -111,7 +117,7 @@ let traslateDeclarationKind ~config ~loc ~outputFileRelative ~resolver
            ->
              let optional, type1 =
                match type_ with
-               | Option type1 -> (Optional, type1)
+               | Option type1 when isOptional nameRE -> (Optional, type1)
                | _ -> (Mandatory, type_)
              in
              {mutable_; nameJS; nameRE; optional; type_ = type1})
@@ -196,9 +202,10 @@ let traslateDeclarationKind ~config ~loc ~outputFileRelative ~resolver
     in
     {translation with type_} |> handleGeneralDeclaration
     |> returnTypeDeclaration
-  | RecordDeclarationFromTypes labelDeclarations, None ->
+  | RecordDeclarationFromTypes (labelDeclarations, recordRepresentation), None
+    ->
     let {TranslateTypeExprFromTypes.dependencies; type_} =
-      labelDeclarations |> translateLabelDeclarations
+      labelDeclarations |> translateLabelDeclarations ~recordRepresentation
     in
     let importTypes =
       dependencies
@@ -227,7 +234,11 @@ let traslateDeclarationKind ~config ~loc ~outputFileRelative ~resolver
                  |> TranslateTypeExprFromTypes.translateTypeExprsFromTypes
                       ~config ~typeEnv
                | Cstr_record labelDeclarations ->
-                 [labelDeclarations |> translateLabelDeclarations]
+                 [
+                   labelDeclarations
+                   |> translateLabelDeclarations
+                        ~recordRepresentation:Types.Record_regular;
+                 ]
              in
              let inlineRecord =
                match constructorArgs with
@@ -342,8 +353,8 @@ let translateTypeDeclaration ~config ~outputFileRelative ~recursive ~resolver
   in
   let declarationKind =
     match typ_type.type_kind with
-    | Type_record (labelDeclarations, _) ->
-      RecordDeclarationFromTypes labelDeclarations
+    | Type_record (labelDeclarations, recordRepresentation) ->
+      RecordDeclarationFromTypes (labelDeclarations, recordRepresentation)
     | Type_variant constructorDeclarations ->
       VariantDeclarationFromTypes constructorDeclarations
     | Type_abstract -> GeneralDeclaration typ_manifest