[Repo Assist] Add PreferOptionals parameter to XmlProvider and JsonProvider

RELEASE_NOTES.md

@@ -1,5 +1,9 @@
 # Release Notes
 
+## 8.1.0-beta
+
+- Add `PreferOptionals` parameter to `JsonProvider` and `XmlProvider` (defaults to `true` to match existing behavior; set to `false` to use empty string or `NaN` for missing values, like the CsvProvider default) (closes #649)
+
 ## 8.0.0 - Feb 25 2026
 
 - Add PreferFloats static parameter to CsvProvider (#1655)

src/AssemblyInfo.Csv.Core.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Csv.Core")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Csv.Core"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.DesignTime.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.DesignTime")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.DesignTime"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.Html.Core.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Html.Core")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Html.Core"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.Http.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Http")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Http"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.Json.Core.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Json.Core")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Json.Core"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.Runtime.Utilities.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Runtime.Utilities")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Runtime.Utilities"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.WorldBank.Core.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.WorldBank.Core")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.WorldBank.Core"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.Xml.Core.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data.Xml.Core")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data.Xml.Core"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

src/AssemblyInfo.fs

@@ -5,13 +5,13 @@ open System.Reflection
 [<assembly: AssemblyTitleAttribute("FSharp.Data")>]
 [<assembly: AssemblyProductAttribute("FSharp.Data")>]
 [<assembly: AssemblyDescriptionAttribute("Library of F# type providers and data access tools")>]
-[<assembly: AssemblyVersionAttribute("8.0.0.0")>]
-[<assembly: AssemblyFileVersionAttribute("8.0.0.0")>]
+[<assembly: AssemblyVersionAttribute("8.1.0.0")>]
+[<assembly: AssemblyFileVersionAttribute("8.1.0.0")>]
 do ()
 
 module internal AssemblyVersionInformation =
     let [<Literal>] AssemblyTitle = "FSharp.Data"
     let [<Literal>] AssemblyProduct = "FSharp.Data"
     let [<Literal>] AssemblyDescription = "Library of F# type providers and data access tools"
-    let [<Literal>] AssemblyVersion = "8.0.0.0"
-    let [<Literal>] AssemblyFileVersion = "8.0.0.0"
+    let [<Literal>] AssemblyVersion = "8.1.0.0"
+    let [<Literal>] AssemblyFileVersion = "8.1.0.0"

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

@@ -60,6 +60,7 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
         let preferDateOnly = args.[11] :?> bool
         let useOriginalNames = args.[12] :?> bool
         let omitNullFields = args.[13] :?> bool
+        let preferOptionals = args.[14] :?> bool
 
         let inferenceMode =
             InferenceMode'.FromPublicApi(inferenceMode, inferTypesFromValues)
@@ -100,8 +101,14 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
 
                         samples
                         |> Array.map (fun sampleJson ->
-                            JsonInference.inferType unitsOfMeasureProvider inferenceMode cultureInfo "" sampleJson)
-                        |> Array.fold (StructuralInference.subtypeInfered false) InferedType.Top
+                            JsonInference.inferType
+                                unitsOfMeasureProvider
+                                inferenceMode
+                                cultureInfo
+                                (not preferOptionals)
+                                ""
+                                sampleJson)
+                        |> Array.fold (StructuralInference.subtypeInfered (not preferOptionals)) InferedType.Top
 #if NET6_0_OR_GREATER
                 if preferDateOnly && ProviderHelpers.runtimeSupportsNet6Types cfg.RuntimeAssembly then
                     rawInfered
@@ -170,7 +177,8 @@ 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("OmitNullFields", typeof<bool>, parameterDefaultValue = false) ]
+          ProvidedStaticParameter("OmitNullFields", typeof<bool>, parameterDefaultValue = false)
+          ProvidedStaticParameter("PreferOptionals", typeof<bool>, parameterDefaultValue = true) ]
 
     let helpText =
         """<summary>Typed representation of a JSON document.</summary>
@@ -196,7 +204,8 @@ type public JsonProvider(cfg: TypeProviderConfig) as this =
            <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='OmitNullFields'>When true, optional fields with value None are omitted from the generated JSON rather than serialized as null. 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>
+           <param name='PreferOptionals'>When set to true (default), inference will use the option type for missing or null values. When false, inference will prefer to use empty string or double.NaN for missing values where possible, matching the default CsvProvider behavior.</param>"""
 
     do jsonProvTy.AddXmlDoc helpText
     do jsonProvTy.DefineStaticParameters(parameters, buildTypes)

src/FSharp.Data.DesignTime/Xml/XmlProvider.fs

@@ -53,6 +53,7 @@ type public XmlProvider(cfg: TypeProviderConfig) as this =
         let preferDateOnly = args.[10] :?> bool
         let dtdProcessing = args.[11] :?> string
         let useOriginalNames = args.[12] :?> bool
+        let preferOptionals = args.[13] :?> bool
 
         let inferenceMode =
             InferenceMode'.FromPublicApi(inferenceMode, inferTypesFromValues)
@@ -133,9 +134,9 @@ type public XmlProvider(cfg: TypeProviderConfig) as this =
                             unitsOfMeasureProvider
                             inferenceMode
                             (TextRuntime.GetCulture cultureStr)
-                            false
+                            (not preferOptionals)
                             globalInference
-                        |> Array.fold (StructuralInference.subtypeInfered false) InferedType.Top
+                        |> Array.fold (StructuralInference.subtypeInfered (not preferOptionals)) InferedType.Top
 #if NET6_0_OR_GREATER
                     if preferDateOnly && ProviderHelpers.runtimeSupportsNet6Types cfg.RuntimeAssembly then
                         t
@@ -203,7 +204,8 @@ type public XmlProvider(cfg: TypeProviderConfig) as this =
           )
           ProvidedStaticParameter("PreferDateOnly", typeof<bool>, parameterDefaultValue = false)
           ProvidedStaticParameter("DtdProcessing", typeof<string>, parameterDefaultValue = "Ignore")
-          ProvidedStaticParameter("UseOriginalNames", typeof<bool>, parameterDefaultValue = false) ]
+          ProvidedStaticParameter("UseOriginalNames", typeof<bool>, parameterDefaultValue = false)
+          ProvidedStaticParameter("PreferOptionals", typeof<bool>, parameterDefaultValue = true) ]
 
     let helpText =
         """<summary>Typed representation of a XML file.</summary>
@@ -229,7 +231,8 @@ type public XmlProvider(cfg: TypeProviderConfig) as this =
            </param>
            <param name='PreferDateOnly'>When true on .NET 6+, date-only strings are inferred as DateOnly and time-only strings as TimeOnly. Defaults to false for backward compatibility.</param>
            <param name='DtdProcessing'>Controls how DTD declarations in the XML are handled. Accepted values: "Ignore" (default, silently skips DTD processing, safe for most cases), "Prohibit" (throws on any DTD declaration), "Parse" (enables full DTD processing including entity expansion, use with caution).</param>
-           <param name='UseOriginalNames'>When true, XML element and attribute names are used as-is for generated property names instead of being normalized to PascalCase. Defaults to false.</param>"""
+           <param name='UseOriginalNames'>When true, XML element and attribute names are used as-is for generated property names instead of being normalized to PascalCase. Defaults to false.</param>
+           <param name='PreferOptionals'>When set to true (default), inference will use the option type for missing or absent values. When false, inference will prefer to use empty string or double.NaN for missing values where possible, matching the default CsvProvider behavior.</param>"""
 
 
     do xmlProvTy.AddXmlDoc helpText

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

@@ -14,7 +14,7 @@ open FSharp.Data.Runtime.StructuralInference
 /// functionality is handled in `StructureInference` (most notably, by
 /// `inferCollectionType` and various functions to find common subtype), so
 /// here we just need to infer types of primitive JSON values.
-let rec internal inferType unitsOfMeasureProvider inferenceMode cultureInfo parentName json =
+let rec internal inferType unitsOfMeasureProvider inferenceMode cultureInfo allowEmptyValues parentName json =
     let inline inRangeDecimal lo hi (v: decimal) : bool = (v >= decimal lo) && (v <= decimal hi)
     let inline inRangeFloat lo hi (v: float) : bool = (v >= float lo) && (v <= float hi)
     let inline isIntegerDecimal (v: decimal) : bool = Math.Round v = v
@@ -65,8 +65,15 @@ let rec internal inferType unitsOfMeasureProvider inferenceMode cultureInfo pare
     // More interesting types
     | JsonValue.Array ar ->
         StructuralInference.inferCollectionType
-            false
-            (Seq.map (inferType unitsOfMeasureProvider inferenceMode cultureInfo (NameUtils.singularize parentName)) ar)
+            allowEmptyValues
+            (Seq.map
+                (inferType
+                    unitsOfMeasureProvider
+                    inferenceMode
+                    cultureInfo
+                    allowEmptyValues
+                    (NameUtils.singularize parentName))
+                ar)
     | JsonValue.Record properties ->
         let name =
             if String.IsNullOrEmpty parentName then
@@ -76,7 +83,9 @@ let rec internal inferType unitsOfMeasureProvider inferenceMode cultureInfo pare
 
         let props =
             [ for propName, value in properties ->
-                  let t = inferType unitsOfMeasureProvider inferenceMode cultureInfo propName value
+                  let t =
+                      inferType unitsOfMeasureProvider inferenceMode cultureInfo allowEmptyValues propName value
+
                   { Name = propName; Type = t } ]
 
         InferedType.Record(name, props, false)

src/FSharp.Data.Xml.Core/XmlInference.fs

@@ -56,6 +56,7 @@ let getInferedTypeFromValue unitsOfMeasureProvider inferenceMode cultureInfo (el
                             unitsOfMeasureProvider
                             inferenceMode
                             cultureInfo
+                            false
                             element.Name.LocalName
 
                     InferedType.Json(jsonType, optional)