fix: fix option serialization (#27)

pchalamet · web-flow · commit e3af602afdc9 · 2026-01-18T12:17:00.000+01:00
diff --git a/.github/workflows/on-push-branch.yml b/.github/workflows/on-push-branch.yml
@@ -17,7 +17,7 @@ jobs:
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v4.2.0
         with:
-          dotnet-version: 9.0.100
+          dotnet-version: 9.0.203
   
       - name: Build & Test
         run: make test config=Release
diff --git a/.github/workflows/on-push-tag.yml b/.github/workflows/on-push-tag.yml
@@ -24,7 +24,7 @@ jobs:
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v4.2.0
         with:
-          dotnet-version: 9.0.100
+          dotnet-version: 9.0.203
 
       - name: Extract Version Suffix
         run: |
diff --git a/.github/workflows/on-release-published.yml b/.github/workflows/on-release-published.yml
@@ -13,7 +13,7 @@ jobs:
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v4.2.0
         with:
-          dotnet-version: 9.0.100
+          dotnet-version: 9.0.203
 
       - name: Download Release artifacts
         uses: robinraju/release-downloader@v1.11
diff --git a/Makefile b/Makefile
@@ -10,3 +10,6 @@ test:
 
 nuget:
 	dotnet pack -c $(config) -p:Version=$(version) -o .out
+
+upgrade:
+	dotnet restore --force-evaluate
diff --git a/README.md b/README.md
@@ -21,7 +21,9 @@ Repository origins are:
 
 ## Supported platforms
 
-This project targets `netstandard2.1` ([compatible runtimes](https://learn.microsoft.com/en-us/dotnet/standard/net-standard?tabs=net-standard-2-1#select-net-standard-version)). 
+This project targets `.net 8`, `.net 9` and  `netstandard2.1` ([compatible runtimes](https://learn.microsoft.com/en-us/dotnet/standard/net-standard?tabs=net-standard-2-1#select-net-standard-version))
+
+:warning: NRT support starts with `.net sdk 9.0.200`. F# compiler in .net sdk 9.0.10x does not set correctly nullable attributes on F# types. NRT are not supported on `netstandard2.1`.
 
 ## Contributing
   * If you have a question about the library, then create an [issue][issues] with the `question` label.
@@ -89,7 +91,9 @@ NRT are serialized as:
 * `null` if `Null`
 * `object` if `NonNull` object
 
-:warning: As of now, NRT can't be considered `null` when deserializing if value is missing.
+On deserialization, missing value is mapped to `null`.
+
+:warning: NRT support starts with .net sdk 9.0.200. F# compiler in .net sdk 9.0.10x does not set correctly nullable attributes on F# types.
 
 # License
 The contents of this library are made available under the [Apache License, Version 2.0][license].
diff --git a/global.json b/global.json
@@ -0,0 +1,5 @@
+{
+    "sdk": {
+      "version": "9.0.203"
+    }
+  }
diff --git a/src/FSharp.MongoDB.Bson/FSharp.MongoDB.Bson.fsproj b/src/FSharp.MongoDB.Bson/FSharp.MongoDB.Bson.fsproj
@@ -1,7 +1,7 @@
-﻿<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net9.0;netstandard2.1</TargetFrameworks>
+    <TargetFrameworks>net9.0;net8.0;netstandard2.1</TargetFrameworks>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <Nullable>enable</Nullable>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
@@ -26,7 +26,7 @@
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="MongoDB.Bson" Version="3.1.0" />
+    <PackageReference Include="MongoDB.Bson" Version="3.4.0" />
   </ItemGroup>
 
   <PropertyGroup>
diff --git a/src/FSharp.MongoDB.Bson/Serialization/Conventions/FSharpRecordConvention.fs b/src/FSharp.MongoDB.Bson/Serialization/Conventions/FSharpRecordConvention.fs
@@ -31,12 +31,12 @@ type FSharpRecordConvention() =
             match classMap.ClassType with
             | IsRecord typ ->
                 let fields = FSharpType.GetRecordFields(typ, bindingFlags)
-                let names = fields |> Array.map (fun x -> x.Name)
+                let names = fields |> Array.map _.Name
 
                 // Map the constructor of the record type.
                 let ctor = FSharpValue.PreComputeRecordConstructorInfo(typ, bindingFlags)
                 classMap.MapConstructor(ctor, names) |> ignore
 
                 // Map each field of the record type.
-                fields |> Array.iter (classMap.MapMember >> ignore)
+                fields |> Array.iter (mapMemberNullable classMap)
             | _ -> ()
diff --git a/src/FSharp.MongoDB.Bson/Serialization/Conventions/UnionCaseConvention.fs b/src/FSharp.MongoDB.Bson/Serialization/Conventions/UnionCaseConvention.fs
@@ -65,7 +65,7 @@ type UnionCaseConvention() =
 
     let mapUnionCase (classMap:BsonClassMap) (unionCase:UnionCaseInfo) =
         let fields = unionCase.GetFields()
-        let names = fields |> Array.map (fun x -> x.Name)
+        let names = fields |> Array.map _.Name
 
         classMap.SetDiscriminator unionCase.Name
         classMap.SetDiscriminatorIsRequired true
@@ -76,7 +76,7 @@ type UnionCaseConvention() =
         classMap.MapCreator(del, names) |> ignore
 
         // Map each field of the union case.
-        fields |> Array.iter (classMap.MapMember >> ignore)
+        fields |> Array.iter (mapMemberNullable classMap)
 
     interface IClassMapConvention with
         member _.Apply classMap =
diff --git a/src/FSharp.MongoDB.Bson/Serialization/FSharpTypeHelpers.fs b/src/FSharp.MongoDB.Bson/Serialization/FSharpTypeHelpers.fs
@@ -23,6 +23,10 @@ module private Helpers =
 
     let bindingFlags = BindingFlags.Public ||| BindingFlags.NonPublic
 
+#if !NETSTANDARD2_1
+    let nrtContext = NullabilityInfoContext()
+#endif
+
     /// <summary>
     /// Returns <c>Some typ</c> when <c>pred typ</c> returns true, and <c>None</c> when
     /// <c>pred typ</c> returns false.
@@ -90,3 +94,16 @@ module private Helpers =
     /// Creates a generic type <c>'T</c> using the generic arguments of <c>typ</c>.
     /// </summary>
     let mkGenericUsingDef<'T> (typ:System.Type) = typ.GetGenericArguments() |> mkGeneric<'T>
+
+    /// <summary>
+    /// Maps a member of a <c>BsonClassMap</c> to a nullable value if possible.
+    /// </summary>
+    let mapMemberNullable (classMap: BsonClassMap) (propertyInfo: PropertyInfo) =
+        let memberMap = classMap.MapMember(propertyInfo)
+#if !NETSTANDARD2_1
+        let nrtInfo = nrtContext.Create(propertyInfo)
+        if nrtInfo.ReadState = NullabilityState.Nullable then
+            memberMap.SetDefaultValue(objnull) |> ignore
+#else
+        memberMap.SetDefaultValue(objnull) |> ignore
+#endif
diff --git a/src/FSharp.MongoDB.Bson/Serialization/FSharpValueSerializer.fs b/src/FSharp.MongoDB.Bson/Serialization/FSharpValueSerializer.fs
@@ -33,7 +33,7 @@ module FSharp =
             member _.GetSerializer typ =
                 let mkSerializer typ = 
                     typ
-                    |> Option.map (fun typ -> System.Activator.CreateInstance typ :?> IBsonSerializer)
+                    |> Option.map (fun typ -> System.Activator.CreateInstance typ |> nonNull :?> IBsonSerializer)
                     |> Option.toObj
 
                 match typ with
diff --git a/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpOptionSerializer.fs b/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpOptionSerializer.fs
@@ -26,7 +26,8 @@ open MongoDB.Bson.Serialization.Serializers
 type FSharpOptionSerializer<'T when 'T: not null>() =
     inherit SerializerBase<'T option>()
 
-    let serializer = lazy (BsonSerializer.LookupSerializer<'T>())
+    let serializer : Lazy<IBsonSerializer<'T>> =
+        lazy (BsonSerializer.LookupSerializer<'T>())
 
     override _.Serialize (context, args, value) =
         let writer = context.Writer
@@ -40,4 +41,6 @@ type FSharpOptionSerializer<'T when 'T: not null>() =
 
         match reader.GetCurrentBsonType() with
         | BsonType.Null -> reader.ReadNull(); None
-        | _ -> Some (serializer.Value.Deserialize(context, args))
+        | _ ->
+            // Use the inner serializer's nominal type to avoid recursing through the option serializer.
+            Some (serializer.Value.Deserialize(context))
diff --git a/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpUnionSerializer.fs b/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpUnionSerializer.fs
@@ -38,7 +38,7 @@ type FSharpUnionSerializer<'T>() =
         let mkClassMapSerializer (caseType:System.Type) =
             let classMap = BsonClassMap.LookupClassMap caseType
             let serializerType = typedefof<BsonClassMapSerializer<_>>.MakeGenericType [| caseType |]
-            System.Activator.CreateInstance(serializerType, classMap) :?> IBsonSerializer
+            System.Activator.CreateInstance(serializerType, classMap) |> nonNull :?> IBsonSerializer
 
         // 8.5.4. Compiled Form of Union Types for Use from Other CLI Languages
         //   A compiled union type U has [o]ne CLI nested type U.C for each non-null union case C.
diff --git a/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpValueOptionSerializer.fs b/src/FSharp.MongoDB.Bson/Serialization/Serializers/FSharpValueOptionSerializer.fs
@@ -26,18 +26,23 @@ open MongoDB.Bson.Serialization.Serializers
 type FSharpValueOptionSerializer<'T when 'T: not null>() =
     inherit SerializerBase<'T voption>()
 
-    let serializer = lazy (BsonSerializer.LookupSerializer<'T>())
+    let serializer : Lazy<IBsonSerializer<'T>> =
+        lazy (BsonSerializer.LookupSerializer<'T>())
 
     override _.Serialize (context, args, value) =
         let writer = context.Writer
 
         match value with
-        | ValueSome x -> serializer.Value.Serialize(context, args, x :> obj)
+        | ValueSome x ->
+            // Serialize using the inner serializer's nominal type.
+            serializer.Value.Serialize(context, x)
         | ValueNone -> writer.WriteNull()
 
     override _.Deserialize (context, args) =
         let reader = context.Reader
 
         match reader.GetCurrentBsonType() with
         | BsonType.Null -> reader.ReadNull(); ValueNone
-        | _ -> ValueSome (serializer.Value.Deserialize(context, args))
+        | _ ->
+            // Use the inner serializer's nominal type to avoid recursing through the option serializer.
+            ValueSome (serializer.Value.Deserialize(context))
diff --git a/tests/CSharpDataModels/CSharpDataModels.csproj b/tests/CSharpDataModels/CSharpDataModels.csproj
@@ -1,4 +1,4 @@
-﻿<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
     <PropertyGroup>
         <TargetFramework>net9.0</TargetFramework>
@@ -8,7 +8,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="MongoDB.Bson" Version="3.1.0" />
+        <PackageReference Include="MongoDB.Bson" Version="3.4.0" />
     </ItemGroup>
 
 </Project>
diff --git a/tests/CSharpDataModels/DataModels.cs b/tests/CSharpDataModels/DataModels.cs
@@ -18,25 +18,25 @@ public record PairValue(Pair Value) : Value;
 
 public record RecordDataModel
 {
-    public ObjectId Id { get; init; }
-
-    public required int Int { get; init; }
-    public int? IntOpt { get; init; }
-
-    public required string String { get; init; }
-    public string? StringOpt { get; init; }
-
-    public required int[] Array { get; init; }
-    public int[]? ArrayOpt { get; init; }
-
-    public required Value Value { get; init; }
-    public Value? ValueOpt { get; init; }
-
-    public required Value[] ValueArray { get; init; }
-    public Value[]? ValueArrayOpt { get; init; }
-
-    public required Pair Record { get; init; }
+    // public ObjectId Id { get; init; }
+    //
+    // public required int Int { get; init; }
+    // public int? IntOpt { get; init; }
+    //
+    // public required string String { get; init; }
+    // public string? StringOpt { get; init; }
+    //
+    // public required int[] Array { get; init; }
+    // public int[]? ArrayOpt { get; init; }
+
+    // public required Value Value { get; init; }
+    // public Value? ValueOpt { get; init; }
+
+    // public required Value[] ValueArray { get; init; }
+    // public Value[]? ValueArrayOpt { get; init; }
+
+    // public required Pair Record { get; init; }
     public Pair? RecordOpt { get; init; }
 
-    public required Dictionary<string, int> Map { get; init; }
+    // public required Dictionary<string, int> Map { get; init; }
 }
diff --git a/tests/FSharp.MongoDB.Bson.Tests/FSharp.MongoDB.Bson.Tests.fsproj b/tests/FSharp.MongoDB.Bson.Tests/FSharp.MongoDB.Bson.Tests.fsproj
@@ -1,4 +1,4 @@
-﻿<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>net9.0</TargetFramework>
@@ -20,20 +20,17 @@
     <Compile Include="Isomorphic\IsomorphicTests.fs" />
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="MongoDB.Bson" Version="3.1.0" />
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\..\src\FSharp.MongoDB.Bson\FSharp.MongoDB.Bson.fsproj" />
     <ProjectReference Include="..\CSharpDataModels\CSharpDataModels.csproj" />
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="FsUnit" Version="6.0.1" />
-    <PackageReference Include="NUnit" Version="4.2.2" />
-    <PackageReference Include="NUnit3TestAdapter" Version="4.6.0" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
+    <PackageReference Include="FsUnit" Version="7.0.1" />
+    <PackageReference Include="NUnit" Version="4.3.2" />
+    <PackageReference Include="NUnit3TestAdapter" Version="5.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.0" />
+    <PackageReference Include="MongoDB.Bson" Version="3.4.0" />
   </ItemGroup>
 
 </Project>
diff --git a/tests/FSharp.MongoDB.Bson.Tests/Isomorphic/IsomorphicTests.fs b/tests/FSharp.MongoDB.Bson.Tests/Isomorphic/IsomorphicTests.fs
diff --git a/tests/FSharp.MongoDB.Bson.Tests/Serialization/FSharpNRTSerializationTests.fs b/tests/FSharp.MongoDB.Bson.Tests/Serialization/FSharpNRTSerializationTests.fs
diff --git a/tests/FSharp.MongoDB.Bson.Tests/Serialization/FSharpOptionSerializationTests.fs b/tests/FSharp.MongoDB.Bson.Tests/Serialization/FSharpOptionSerializationTests.fs

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +{
 +    "sdk": {
 +      "version": "9.0.203"
 +    }
 +  }