Add nullable support to JSON generators (#174)

WoofWare.Myriad.Plugins/JsonParseGenerator.fs

@@ -95,17 +95,6 @@ module internal JsonParseGenerator =
         )
         |> SynExpr.pipeThroughFunction (SynExpr.createLongIdent [ collectionType ; "ofSeq" ])
 
-    /// match {node} with | null -> None | v -> {body} |> Some
-    /// Use the variable `v` to get access to the `Some`.
-    let createParseLineOption (node : SynExpr) (body : SynExpr) : SynExpr =
-        let body = SynExpr.pipeThroughFunction (SynExpr.createIdent "Some") body
-
-        [
-            SynMatchClause.create SynPat.createNull (SynExpr.createIdent "None")
-            SynMatchClause.create (SynPat.named "v") body
-        ]
-        |> SynExpr.createMatch node
-
     let dotParse (typeName : LongIdent) : LongIdent =
         List.append typeName [ Ident.create "Parse" ]
 
@@ -206,8 +195,29 @@ module internal JsonParseGenerator =
         | NumberType typeName -> parseNumberType options propertyName node typeName
         | PrimitiveType typeName -> asValueGetValueIdent propertyName typeName node
         | OptionType ty ->
-            parseNode None options ty (SynExpr.createIdent "v")
-            |> createParseLineOption node
+            let someClause =
+                parseNode None options ty (SynExpr.createIdent "v")
+                |> SynExpr.pipeThroughFunction (SynExpr.createIdent "Some")
+                |> SynMatchClause.create (SynPat.named "v")
+
+            [
+                SynMatchClause.create SynPat.createNull (SynExpr.createIdent "None")
+                someClause
+            ]
+            |> SynExpr.createMatch node
+        | NullableType ty ->
+            let someClause =
+                parseNode None options ty (SynExpr.createIdent "v")
+                |> SynExpr.pipeThroughFunction (SynExpr.createLongIdent [ "System" ; "Nullable" ])
+                |> SynMatchClause.create (SynPat.named "v")
+
+            [
+                SynMatchClause.create
+                    SynPat.createNull
+                    (SynExpr.applyFunction (SynExpr.createLongIdent [ "System" ; "Nullable" ]) (SynExpr.CreateConst ()))
+                someClause
+            ]
+            |> SynExpr.createMatch node
         | ListType ty ->
             parseNode None options ty (SynExpr.createIdent "elt")
             |> asArrayMapped propertyName "List" node

WoofWare.Myriad.Plugins/JsonSerializeGenerator.fs

@@ -13,6 +13,14 @@ type internal JsonSerializeOutputSpec =
 module internal JsonSerializeGenerator =
     open Fantomas.FCS.Text.Range
 
+
+    // The absolutely galaxy-brained implementation of JsonValue has `JsonValue.Parse "null"`
+    // identically equal to null. We have to work around this later, but we might as well just
+    // be efficient here and whip up the null directly.
+    let private jsonNull () =
+        SynExpr.createNull ()
+        |> SynExpr.upcast' (SynType.createLongIdent' [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonNode" ])
+
     /// Given `input.Ident`, for example, choose how to add it to the ambient `node`.
     /// The result is a line like `(fun ident -> InnerType.toJsonNode ident)` or `(fun ident -> JsonValue.Create ident)`.
     let rec serializeNode (fieldType : SynType) : SynExpr =
@@ -35,15 +43,15 @@ module internal JsonSerializeGenerator =
                 range0,
                 range0
             )
+        | NullableType ty ->
+            // fun field -> if field.HasValue then {serializeNode ty} field.Value else JsonValue.Create null
+            SynExpr.applyFunction (serializeNode ty) (SynExpr.createLongIdent [ "field" ; "Value" ])
+            |> SynExpr.upcast' (SynType.createLongIdent' [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonNode" ])
+            |> SynExpr.ifThenElse (SynExpr.createLongIdent [ "field" ; "HasValue" ]) (jsonNull ())
+            |> SynExpr.createLambda "field"
         | OptionType ty ->
             // fun field -> match field with | None -> JsonValue.Create null | Some v -> {serializeNode ty} field
-            let noneClause =
-                // The absolutely galaxy-brained implementation of JsonValue has `JsonValue.Parse "null"`
-                // identically equal to null. We have to work around this later, but we might as well just
-                // be efficient here and whip up the null directly.
-                SynExpr.createNull ()
-                |> SynExpr.upcast' (SynType.createLongIdent' [ "System" ; "Text" ; "Json" ; "Nodes" ; "JsonNode" ])
-                |> SynMatchClause.create (SynPat.named "None")
+            let noneClause = jsonNull () |> SynMatchClause.create (SynPat.named "None")
 
             let someClause =
                 SynExpr.applyFunction (serializeNode ty) (SynExpr.createIdent "field")
@@ -140,9 +148,10 @@ module internal JsonSerializeGenerator =
     let createSerializeRhsRecord (propertyName : SynExpr) (fieldId : Ident) (fieldType : SynType) : SynExpr =
         [
             propertyName
-            SynExpr.applyFunction
+            SynExpr.pipeThroughFunction
                 (serializeNode fieldType)
                 (SynExpr.createLongIdent' [ Ident.create "input" ; fieldId ])
+            |> SynExpr.paren
         ]
         |> SynExpr.tuple
         |> SynExpr.applyFunction (SynExpr.createLongIdent [ "node" ; "Add" ])

WoofWare.Myriad.Plugins/SynExpr/SynExpr.fs

@@ -106,15 +106,16 @@ module internal SynExpr =
         | SynExpr.Paren (expr, _, _, _) -> stripOptionalParen expr
         | expr -> expr
 
-    /// {obj}.{meth} {arg}
-    let callMethodArg (meth : string) (arg : SynExpr) (obj : SynExpr) : SynExpr =
+    let dotGet (field : string) (obj : SynExpr) : SynExpr =
         SynExpr.DotGet (
             obj,
             range0,
-            SynLongIdent.SynLongIdent (id = [ Ident.create meth ], dotRanges = [], trivia = [ None ]),
+            SynLongIdent.SynLongIdent (id = [ Ident.create field ], dotRanges = [], trivia = [ None ]),
             range0
         )
-        |> applyTo arg
+
+    /// {obj}.{meth} {arg}
+    let callMethodArg (meth : string) (arg : SynExpr) (obj : SynExpr) : SynExpr = dotGet meth obj |> applyTo arg
 
     /// {obj}.{meth}()
     let callMethod (meth : string) (obj : SynExpr) : SynExpr =

WoofWare.Myriad.Plugins/SynExpr/SynLongIdent.fs

@@ -70,6 +70,12 @@ module internal SynLongIdent =
         // TODO: consider Microsoft.FSharp.Option or whatever it is
         | _ -> false
 
+    let isNullable (ident : SynLongIdent) : bool =
+        match ident.LongIdent |> List.map _.idText with
+        | [ "System" ; "Nullable" ]
+        | [ "Nullable" ] -> true
+        | _ -> false
+
     let isResponse (ident : SynLongIdent) : bool =
         match ident.LongIdent |> List.map _.idText with
         | [ "Response" ]

WoofWare.Myriad.Plugins/SynExpr/SynType.fs

@@ -59,6 +59,12 @@ module internal SynTypePatterns =
             Some innerType
         | _ -> None
 
+    let (|NullableType|_|) (fieldType : SynType) =
+        match fieldType with
+        | SynType.App (SynType.LongIdent ident, _, [ innerType ], _, _, _, _) when SynLongIdent.isNullable ident ->
+            Some innerType
+        | _ -> None
+
     let (|UnitType|_|) (fieldType : SynType) : unit option =
         match fieldType with
         | SynType.LongIdent ident when SynLongIdent.isUnit ident -> Some ()