experimental - allow payloadless variant constructors in input unions

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## main
 
+- _experimental_ Allow payloadless variant cases in input unions.
+
 ## 0.13.2
 
 - Fix bug when input objects and input unions were mixed.

src/ml/GenerateSchema.ml

@@ -333,6 +333,12 @@ let rec findGraphQLType ~(env : SharedTypes.QueryEnv.t)
                             match c.args with
                             | InlineRecord _ -> Some c.cname.txt
                             | _ -> None);
+                   emptyPayloads =
+                     cases
+                     |> List.filter_map (fun (c : SharedTypes.Constructor.t) ->
+                            match c.args with
+                            | Args [] -> Some c.cname.txt
+                            | _ -> None);
                  })
           | Some (InterfaceResolver {interfaceId}), {kind = Variant _} ->
             Some
@@ -896,6 +902,16 @@ and variantCasesToInputUnionValues ~env ~debug ~schemaState ~full ~ownerName
              }
            in
            Some member
+         | Args [] ->
+           Some
+             {
+               typ = EmptyPayload;
+               fieldName = uncapitalizeFirstChar case.cname.txt;
+               loc = case.cname.loc;
+               description =
+                 case.attributes |> ProcessAttributes.findDocAttribute;
+               constructorName = case.cname.txt;
+             }
          | Args [(typ, _)] -> (
            (* TODO: Validate more that only input types are present. *)
            match

src/ml/GenerateSchemaSDL.ml

@@ -13,6 +13,7 @@ let rec graphqlTypeToString ?(nullable = false) (t : graphqlType) =
   let nullableSuffix = if nullable = false then "!" else "" in
   match t with
   | Scalar scalar -> scalarToString scalar ^ nullableSuffix
+  | EmptyPayload -> graphqlTypeToString ~nullable:true (Scalar Boolean)
   | Nullable inner | RescriptNullable inner ->
     graphqlTypeToString ~nullable:true inner
   | List inner ->

src/ml/GenerateSchemaTypePrinters.ml

@@ -57,6 +57,7 @@ let rec printGraphQLType ?(nullable = false) (returnType : graphqlType) =
       (printGraphQLType inner) nullablePostfix
   | RescriptNullable inner | Nullable inner ->
     printGraphQLType ~nullable:true inner
+  | EmptyPayload -> printGraphQLType ~nullable:true (Scalar Boolean)
   | Scalar scalar ->
     let scalarStr =
       match scalar with
@@ -402,7 +403,7 @@ let printSchemaJsFile schemaState processSchema =
   (* Add the input union unwrapper. TODO: Explain more
   *)
   addWithNewLine
-    {|let inputUnionUnwrapper: ('src, array<string>) => 'return = %raw(`function inputUnionUnwrapper(src, inlineRecordTypenames) {
+    {|let inputUnionUnwrapper: ('src, array<string>, array<string>) => 'return = %raw(`function inputUnionUnwrapper(src, inlineRecordTypenames, emptyPayloadTypenames) {
       if (src == null) return null;
 
       let targetKey = null;
@@ -421,6 +422,10 @@ let printSchemaJsFile schemaState processSchema =
         if (inlineRecordTypenames.includes(tagName)) {
           return Object.assign({ TAG: tagName }, targetValue);
         }
+
+        if (emptyPayloadTypenames.includes(tagName)) {
+          return tagName;
+        }
 
         return {
           TAG: tagName,

src/ml/GenerateSchemaTypes.ml

@@ -5,6 +5,8 @@ type graphqlType =
   | Nullable of graphqlType
   | RescriptNullable of graphqlType
   | Scalar of scalar
+  | EmptyPayload
+      (** Used to represent empty payloads, like constructor-less unions. *)
   | InjectContext
   | InjectInfo
   | InjectInterfaceTypename of string  (** ID of interface *)
@@ -14,6 +16,7 @@ type graphqlType =
       id: string;
       displayName: string;
       inlineRecords: string list;
+      emptyPayloads: string list;
     }
   | GraphQLEnum of {id: string; displayName: string}
   | GraphQLUnion of {id: string; displayName: string}

src/ml/GenerateSchemaUtils.ml

@@ -501,14 +501,18 @@ let rec generateConverter lastValue (graphqlType : graphqlType) =
     Printf.sprintf
       "%s->applyConversionToInputObject(input_%s_conversionInstructions)"
       lastValue displayName
-  | GraphQLInputUnion {displayName; inlineRecords} ->
+  | GraphQLInputUnion {displayName; inlineRecords; emptyPayloads} ->
     (* TODO: Precompute/persist? *)
     Printf.sprintf
-      "%s->applyConversionToInputObject(inputUnion_%s_conversionInstructions)->inputUnionUnwrapper([%s])"
+      "%s->applyConversionToInputObject(inputUnion_%s_conversionInstructions)->inputUnionUnwrapper([%s], \
+       [%s])"
       lastValue displayName
       (inlineRecords
       |> List.map (fun s -> "\"" ^ s ^ "\"")
       |> String.concat ", ")
+      (emptyPayloads
+      |> List.map (fun s -> "\"" ^ s ^ "\"")
+      |> String.concat ", ")
   | _ -> lastValue
 
 let printInputObjectAssets (inputObject : gqlInputObjectType) =

tests/schema.graphql

@@ -236,6 +236,11 @@ input UpdatableNullableInt {
   updateValue: Int
 }
 
+input UnionWithEmptyMember {
+  empty: Boolean
+  string: String
+}
+
 input UpdatableInt {
   leaveUnchanged: Boolean
   updateValue: Int

tests/src/Thing.res

@@ -1,6 +1,6 @@
-type updatableOptions = LeaveUnchanged(bool)
+type updatableOptions = LeaveUnchanged
 
-type updatableOptionsNullable = UnsetValue(bool) | ...updatableOptions
+type updatableOptionsNullable = UnsetValue | ...updatableOptions
 
 @gql.inputUnion
 type updatableNullableString = UpdateValue(string) | ...updatableOptionsNullable
@@ -66,26 +66,26 @@ let updateThing = (_: Mutation.mutation, ~thingId: ResGraph.id, ~input: updateTh
     ...currentThing,
     name: switch input.name {
     | UpdateValue(name) => name
-    | LeaveUnchanged(_) => currentThing.name
+    | LeaveUnchanged => currentThing.name
     },
     age: switch input.age {
     | UpdateValue(age) => age
-    | LeaveUnchanged(_) => currentThing.age
+    | LeaveUnchanged => currentThing.age
     },
     favoriteColor: switch input.favoriteColor {
     | UpdateValue(favoriteColor) => Some(favoriteColor)
-    | LeaveUnchanged(_) => currentThing.favoriteColor
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.favoriteColor
+    | UnsetValue => None
     },
     isAdmin: switch input.isAdmin {
     | UpdateValue(isAdmin) => Some(isAdmin)
-    | LeaveUnchanged(_) => currentThing.isAdmin
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.isAdmin
+    | UnsetValue => None
     },
     height: switch input.height {
     | UpdateValue(height) => Some(height)
-    | LeaveUnchanged(_) => currentThing.height
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.height
+    | UnsetValue => None
     },
   }
 

tests/tests/Schema.res

@@ -429,9 +429,9 @@ let countdown = (_: subscription) => {
   iterator
 }
 
-type updatableOptions = LeaveUnchanged(bool)
+type updatableOptions = LeaveUnchanged
 
-type updatableOptionsNullable = UnsetValue(bool) | ...updatableOptions
+type updatableOptionsNullable = UnsetValue | ...updatableOptions
 
 @gql.inputUnion
 type updatableNullableString = UpdateValue(string) | ...updatableOptionsNullable
@@ -497,28 +497,31 @@ let updateThing = (_: mutation, ~thingId: ResGraph.id, ~input: updateThingInput)
     ...currentThing,
     name: switch input.name {
     | UpdateValue(name) => name
-    | LeaveUnchanged(_) => currentThing.name
+    | LeaveUnchanged => currentThing.name
     },
     age: switch input.age {
     | UpdateValue(age) => age
-    | LeaveUnchanged(_) => currentThing.age
+    | LeaveUnchanged => currentThing.age
     },
     favoriteColor: switch input.favoriteColor {
     | UpdateValue(favoriteColor) => Some(favoriteColor)
-    | LeaveUnchanged(_) => currentThing.favoriteColor
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.favoriteColor
+    | UnsetValue => None
     },
     isAdmin: switch input.isAdmin {
     | UpdateValue(isAdmin) => Some(isAdmin)
-    | LeaveUnchanged(_) => currentThing.isAdmin
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.isAdmin
+    | UnsetValue => None
     },
     height: switch input.height {
     | UpdateValue(height) => Some(height)
-    | LeaveUnchanged(_) => currentThing.height
-    | UnsetValue(_) => None
+    | LeaveUnchanged => currentThing.height
+    | UnsetValue => None
     },
   }
 
   Some(newThing)
 }
+
+@gql.inputUnion
+type unionWithEmptyMember = String(string) | Empty