Immutable dynamic object

DynamicObj.sln

@@ -1,7 +1,7 @@
 
 Microsoft Visual Studio Solution File, Format Version 12.00
-# Visual Studio Version 16
-VisualStudioVersion = 16.0.31515.178
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31521.260
 MinimumVisualStudioVersion = 10.0.40219.1
 Project("{6EC3EE1D-3C4E-46DD-8F32-0CC8E7565705}") = "DynamicObj", "src\DynamicObj\DynamicObj.fsproj", "{B8BF1554-AAC3-434E-9502-FC83B43F3704}"
 EndProject
@@ -38,6 +38,10 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "docs", "docs", "{42AA66FC-8
 		docs\index.fsx = docs\index.fsx
 	EndProjectSection
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "CSharpTests", "tests\CSharpTests\CSharpTests.csproj", "{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D}"
+EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "tests", "tests", "{988D804A-3A42-4E46-B233-B64F5C22524B}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -52,10 +56,18 @@ Global
 		{D009964D-9408-4344-B610-B73F54FE2A86}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{D009964D-9408-4344-B610-B73F54FE2A86}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{D009964D-9408-4344-B610-B73F54FE2A86}.Release|Any CPU.Build.0 = Release|Any CPU
+		{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
 	EndGlobalSection
+	GlobalSection(NestedProjects) = preSolution
+		{D009964D-9408-4344-B610-B73F54FE2A86} = {988D804A-3A42-4E46-B233-B64F5C22524B}
+		{D62D0901-DB69-4C64-AC63-FBBBDCF6BC7D} = {988D804A-3A42-4E46-B233-B64F5C22524B}
+	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {6F5C3597-4524-4A4E-94EC-44857BD0BCEC}
 	EndGlobalSection

src/DynamicObj/DynamicObj.fsproj

@@ -23,8 +23,10 @@
 
   <ItemGroup>
     <Compile Include="ReflectionUtils.fs" />
+    <Compile Include="ImmutableDynamicObj.fs" />
     <Compile Include="DynamicObj.fs" />
     <Compile Include="DynObj.fs" />
+    <Compile Include="Operators.fs" />
     <None Include="Playground.fsx" />
   </ItemGroup>
 

src/DynamicObj/ImmutableDynamicObj.fs

@@ -0,0 +1,105 @@
+namespace DynamicObj
+
+open DynamicObj
+open System.Reflection
+open System.Runtime.CompilerServices
+
+[<InternalsVisibleToAttribute("UnitTests")>]
+do()
+
+/// Represents an DynamicObj's counterpart
+/// with immutability enabled only.
+type ImmutableDynamicObj internal (map : Map<string, obj>) = 
+
+    let mutable properties = map
+
+    member private this.Properties 
+        with get () =
+            properties
+        and set value =
+            properties <- value
+
+    // Copies the fields of one object to the other one
+    // If their base is not ImmutableDynamicObj, then it
+    // will go over fields from the base instance
+    static member private copyMembers (ty : System.Type) sourceObject destinationObject =
+        for fi in ty.GetFields(BindingFlags.Instance ||| BindingFlags.NonPublic ||| BindingFlags.Public) do
+            let fieldValue = fi.GetValue sourceObject
+            fi.SetValue(destinationObject, fieldValue)
+
+    static member private newIfNeeded (object : 'a when 'a :> ImmutableDynamicObj) map : 'a =
+        if obj.ReferenceEquals(map, object.Properties) then
+            object
+        else
+            // otherwise we create a new instance
+            let res = new 'a()
+
+            // and then copy all current fields the new instance 
+            ImmutableDynamicObj.copyMembers (typeof<'a>) object res
+            res.Properties <- map
+            res
+
+    /// Empty instance
+    new () = ImmutableDynamicObj Map.empty
+
+    static member empty = ImmutableDynamicObj ()
+
+    /// Indexes ; if no key found, throws
+    member this.Item
+        with get(index) =
+            this.Properties.[index]
+
+    /// Returns an instance with:
+    /// 1. this property added if it wasn't present
+    /// 2. this property updated otherwise
+    static member add name newValue (object : #ImmutableDynamicObj) =
+        object.Properties
+        |> Map.add name newValue
+        |> ImmutableDynamicObj.newIfNeeded object
+
+    /// Returns an instance:
+    /// 1. the same if there was no requested property
+    /// 2. without the requested property if there was
+    static member remove name (object : #ImmutableDynamicObj) =
+        object.Properties
+        |> Map.remove name
+        |> ImmutableDynamicObj.newIfNeeded object
+
+    member this.TryGetValue name = 
+        match this.Properties.TryGetValue name with
+        | true, value ->  Some value
+        | _ -> ReflectionUtils.tryGetPropertyValue this name
+
+    member this.TryGetTypedValue<'a> name = 
+        match this.TryGetValue name with
+        | None -> None
+        | Some o -> 
+            match o with
+            | :? 'a as o -> o |> Some
+            | _ -> None
+
+    override this.Equals o =
+        match o with
+        | :? ImmutableDynamicObj as other -> other.Properties = this.Properties
+        | _ -> false
+
+    override this.GetHashCode () = ~~~map.GetHashCode()
+
+[<Extension>]
+type ImmutableDynamicObjExtensions =
+
+    /// Returns an instance with:
+    /// 1. this property added if it wasn't present
+    /// 2. this property updated otherwise
+    /// use this one only from C#
+    [<Extension>]
+    static member AddItem (this, name, newValue) =
+        ImmutableDynamicObj.add name newValue this
+
+    /// Returns an instance:
+    /// 1. the same if there was no requested property
+    /// 2. without the requested property if there was
+    /// use this one only from C#
+    [<Extension>]
+    static member RemoveItem (this, name) =
+        ImmutableDynamicObj.remove name this

src/DynamicObj/Operators.fs

@@ -0,0 +1,29 @@
+module DynamicObj.Operators
+
+
+
+/// Returns an instance with:
+/// 1. this property added if it wasn't present
+/// 2. this property updated otherwise
+let (++) object (name, newValue) = ImmutableDynamicObj.add name newValue object
+
+
+/// Returns an instance:
+/// 1. the same if there was no requested property
+/// 2. without the requested property if there was
+let (--) object name = ImmutableDynamicObj.remove name object
+
+
+/// Acts as (++) if the value is Some,
+/// returns the same object otherwise
+let (++?) object (name, newValue) =
+    match newValue with
+    | Some(value) -> object ++ (name, value)
+    | None -> object
+
+/// Acts as (++?) but maps the valid value 
+/// through the last argument
+let (++??) object (name, newValue, f) =
+    match newValue with
+    | Some(value) -> object ++ (name, f value)
+    | None -> object

tests/CSharpTests/CSharpTests.csproj

@@ -0,0 +1,26 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net5.0</TargetFramework>
+
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
+    <PackageReference Include="xunit" Version="2.4.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="coverlet.collector" Version="3.0.2">
+      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
+      <PrivateAssets>all</PrivateAssets>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\DynamicObj\DynamicObj.fsproj" />
+  </ItemGroup>
+
+</Project>

tests/CSharpTests/InteropWorks.cs

@@ -0,0 +1,58 @@
+using System;
+using Xunit;
+using DynamicObj;
+using Microsoft.FSharp.Collections;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace CSharpTests
+{
+    public class InteropWorks
+    {
+        [Fact]
+        public void Test1()
+        {
+            var obj1 =
+                new ImmutableDynamicObj()
+                .AddItem("aa", 4)
+                .AddItem("bb", 10)
+                .RemoveItem("aa")
+                ;
+            var obj2 = 
+                new ImmutableDynamicObj()
+                .AddItem("bb", 10)
+                ;
+            Assert.Equal(obj1, obj2);
+        }
+
+        public class MyDynamicObject : ImmutableDynamicObj
+        {
+
+        }
+
+        [Fact]
+        public void Test2()
+        {
+            var obj1 =
+                new MyDynamicObject()
+                .AddItem("aaa", 5);
+            Assert.IsType<MyDynamicObject>(obj1);
+            Assert.Equal(5, obj1["aaa"]);
+        }
+
+        public class MyDynamicObjectWithField : ImmutableDynamicObj
+        {
+            public int Aaa { get; init; }
+        }
+
+        [Fact]
+        public void TestFieldsPreservedForInheritor()
+        {
+            var obj1 =
+                new MyDynamicObjectWithField() { Aaa = 100500 }
+                .AddItem("aaa", 5)
+                .RemoveItem("aaa");
+            Assert.Equal(100500, obj1.Aaa);
+        }
+    }
+}