[Repo Assist] Add OmitNullFields static parameter to JsonProvider (closes #1245)

src/FSharp.Data.DesignTime/Json/JsonGenerator.fs

@@ -31,7 +31,8 @@ type internal JsonGenerationContext =
       GenerateConstructors: bool
       InferenceMode: InferenceMode'
       UnitsOfMeasureProvider: IUnitsOfMeasureProvider
-      UseOriginalNames: bool }
+      UseOriginalNames: bool
+      OmitNullFields: bool }
 
     static member Create
         (
@@ -42,7 +43,8 @@ type internal JsonGenerationContext =
             ?uniqueNiceName,
             ?typeCache,
             ?preferDictionaries,
-            ?useOriginalNames
+            ?useOriginalNames,
+            ?omitNullFields
         ) =
         let useOriginalNames = defaultArg useOriginalNames false
 
@@ -53,6 +55,7 @@ type internal JsonGenerationContext =
 
         let typeCache = defaultArg typeCache (Dictionary())
         let preferDictionaries = defaultArg preferDictionaries false
+        let omitNullFields = defaultArg omitNullFields false
 
         JsonGenerationContext.Create(
             cultureStr,
@@ -63,7 +66,8 @@ type internal JsonGenerationContext =
             true,
             inferenceMode,
             unitsOfMeasureProvider,
-            useOriginalNames
+            useOriginalNames,
+            omitNullFields
         )
 
     static member Create
@@ -76,7 +80,8 @@ type internal JsonGenerationContext =
             generateConstructors,
             inferenceMode,
             unitsOfMeasureProvider,
-            useOriginalNames
+            useOriginalNames,
+            omitNullFields
         ) =
         { CultureStr = cultureStr
           TypeProviderType = tpType
@@ -89,7 +94,33 @@ type internal JsonGenerationContext =
           GenerateConstructors = generateConstructors
           InferenceMode = inferenceMode
           UnitsOfMeasureProvider = unitsOfMeasureProvider
-          UseOriginalNames = useOriginalNames }
+          UseOriginalNames = useOriginalNames
+          OmitNullFields = omitNullFields }
+
+    static member Create
+        (
+            cultureStr,
+            tpType,
+            uniqueNiceName,
+            typeCache,
+            preferDictionaries,
+            generateConstructors,
+            inferenceMode,
+            unitsOfMeasureProvider,
+            useOriginalNames
+        ) =
+        JsonGenerationContext.Create(
+            cultureStr,
+            tpType,
+            uniqueNiceName,
+            typeCache,
+            preferDictionaries,
+            generateConstructors,
+            inferenceMode,
+            unitsOfMeasureProvider,
+            useOriginalNames,
+            false
+        )
 
     member x.MakeOptionType(typ: Type) =
         typedefof<option<_>>.MakeGenericType typ
@@ -645,7 +676,11 @@ module JsonTypeBuilder =
                                 )
 
                             let cultureStr = ctx.CultureStr
-                            <@@ JsonRuntime.CreateRecord(%%properties, cultureStr) @@>
+
+                            if ctx.OmitNullFields then
+                                <@@ JsonRuntime.CreateRecordOmitNulls(%%properties, cultureStr) @@>
+                            else
+                                <@@ JsonRuntime.CreateRecord(%%properties, cultureStr) @@>
 
                         let ctor = ProvidedConstructor(parameters, invokeCode = ctorCode)
                         objectTy.AddMember ctor

src/FSharp.Data.DesignTime/Json/JsonProvider.fs

@@ -59,6 +59,7 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
         let schema = args.[10] :?> string
         let preferDateOnly = args.[11] :?> bool
         let useOriginalNames = args.[12] :?> bool
+        let omitNullFields = args.[13] :?> bool
 
         let inferenceMode =
             InferenceMode'.FromPublicApi(inferenceMode, inferTypesFromValues)
@@ -119,7 +120,8 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
                     unitsOfMeasureProvider,
                     inferenceMode,
                     ?preferDictionaries = Some preferDictionaries,
-                    ?useOriginalNames = Some useOriginalNames
+                    ?useOriginalNames = Some useOriginalNames,
+                    ?omitNullFields = Some omitNullFields
                 )
 
             let result = JsonTypeBuilder.generateJsonType ctx false false rootName inferedType
@@ -167,7 +169,8 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
           )
           ProvidedStaticParameter("Schema", typeof<string>, parameterDefaultValue = "")
           ProvidedStaticParameter("PreferDateOnly", typeof<bool>, parameterDefaultValue = false)
-          ProvidedStaticParameter("UseOriginalNames", typeof<bool>, parameterDefaultValue = false) ]
+          ProvidedStaticParameter("UseOriginalNames", typeof<bool>, parameterDefaultValue = false)
+          ProvidedStaticParameter("OmitNullFields", typeof<bool>, parameterDefaultValue = false) ]
 
     let helpText =
         """<summary>Typed representation of a JSON document.</summary>
@@ -192,7 +195,8 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
            </param>
            <param name='Schema'>Location of a JSON Schema file or a string containing a JSON Schema document. When specified, Sample and SampleIsList must not be used.</param>
            <param name='PreferDateOnly'>When true on .NET 6+, date-only strings (e.g. "2023-01-15") are inferred as DateOnly and time-only strings as TimeOnly. Defaults to false for backward compatibility.</param>
-           <param name='UseOriginalNames'>When true, JSON property names are used as-is for generated property names instead of being normalized to PascalCase. Defaults to false.</param>"""
+           <param name='UseOriginalNames'>When true, JSON property names are used as-is for generated property names instead of being normalized to PascalCase. Defaults to false.</param>
+           <param name='OmitNullFields'>When true, optional fields with value None are omitted from the generated JSON rather than serialized as null. Defaults to false.</param>"""
 
     do jsonProvTy.AddXmlDoc helpText
     do jsonProvTy.DefineStaticParameters(parameters, buildTypes)

src/FSharp.Data.Json.Core/JsonRuntime.fs

@@ -351,6 +351,22 @@ type JsonRuntime =
 
         JsonDocument.Create(json, "")
 
+    // Creates a JsonValue.Record, omitting null fields, and wraps it in a json document
+    static member CreateRecordOmitNulls(properties, cultureStr) =
+        let cultureInfo = TextRuntime.GetCulture cultureStr
+
+        let json =
+            properties
+            |> Array.choose (fun (k, v: obj) ->
+                let jv = JsonRuntime.ToJsonValue cultureInfo v
+
+                match jv with
+                | JsonValue.Null -> None
+                | _ -> Some(k, jv))
+            |> JsonValue.Record
+
+        JsonDocument.Create(json, "")
+
     // Creates a JsonValue.Record from key*value seq and wraps it in a json document
     static member CreateRecordFromDictionary<'Key, 'Value when 'Key: equality>
         (keyValuePairs: ('Key * 'Value) seq, cultureStr, mappingKeyBack: Func<'Key, string>)

tests/FSharp.Data.DesignTime.Tests/TypeProviderInstantiation.fs

@@ -57,7 +57,8 @@ type internal JsonProviderArgs =
       InferenceMode: InferenceMode
       Schema: string
       PreferDateOnly : bool
-      UseOriginalNames : bool }
+      UseOriginalNames : bool
+      OmitNullFields : bool }
 
 type internal HtmlProviderArgs =
     { Sample : string
@@ -133,7 +134,8 @@ type internal TypeProviderInstantiation =
                    box x.InferenceMode
                    box x.Schema
                    box x.PreferDateOnly
-                   box x.UseOriginalNames |]
+                   box x.UseOriginalNames
+                   box x.OmitNullFields |]
             | Html x ->
                 (fun cfg -> new HtmlProvider(cfg) :> TypeProviderForNamespaces),
                 [| box x.Sample
@@ -271,7 +273,8 @@ type internal TypeProviderInstantiation =
                        InferenceMode = args.[7] |> InferenceMode.Parse
                        Schema = if args.Length > 8 then args.[8] else ""
                        PreferDateOnly = false
-                       UseOriginalNames = false }
+                       UseOriginalNames = false
+                       OmitNullFields = false }
             else
                 // This is for schema-based tests in the format "Json,,,,,true,false,BackwardCompatible,SimpleSchema.json"
                 Json { Sample = args.[1]
@@ -286,7 +289,8 @@ type internal TypeProviderInstantiation =
                        InferenceMode = InferenceMode.Parse "BackwardCompatible"
                        Schema = if args.Length > 8 then args.[8] else ""
                        PreferDateOnly = false
-                       UseOriginalNames = false }
+                       UseOriginalNames = false
+                       OmitNullFields = false }
         | "Html" ->
             Html { Sample = args.[1]
                    PreferOptionals = args.[2] |> bool.Parse

tests/FSharp.Data.Tests/JsonProvider.fs

@@ -968,3 +968,27 @@ let ``JsonProvider default normalizes property names to PascalCase`` () =
     let doc = JsonNormalizedNames.Parse("""{"first_name": "Jane", "last_name": "Smith"}""")
     doc.FirstName |> should equal "Jane"
     doc.LastName |> should equal "Smith"
+
+type JsonOmitNullFieldsSample = JsonProvider<"""[{"color": "Red", "code": 15}, {"color": "Green"}]""", SampleIsList = true, OmitNullFields = true>
+type JsonIncludeNullFieldsSample = JsonProvider<"""[{"color": "Red", "code": 15}, {"color": "Green"}]""", SampleIsList = true>
+
+[<Test>]
+let ``JsonProvider OmitNullFields=true omits None optional fields from output`` () =
+    let value = JsonOmitNullFieldsSample.Root(color = "Blue", code = None)
+    let json = value.ToString()
+    json |> should not' (contain "null")
+    json |> should not' (contain "code")
+    json |> should contain "Blue"
+
+[<Test>]
+let ``JsonProvider default includes None optional fields as null`` () =
+    let value = JsonIncludeNullFieldsSample.Root(color = "Blue", code = None)
+    let json = value.ToString()
+    json |> should contain "null"
+
+[<Test>]
+let ``JsonProvider OmitNullFields=true includes non-None fields`` () =
+    let value = JsonOmitNullFieldsSample.Root(color = "Blue", code = Some 42)
+    let json = value.ToString()
+    json |> should contain "42"
+    json |> should contain "Blue"