UO set property (#2547)

Issue https://github.com/microsoft/Power-Fx/issues/2501.

src/libraries/Microsoft.PowerFx.Core/Public/Values/FormulaValueNew.cs

@@ -122,6 +122,13 @@ namespace Microsoft.PowerFx.Types
         public static ErrorValue NewError(IEnumerable<ExpressionError> error, FormulaType type)
         {
             return new ErrorValue(IRContext.NotInSource(type), error.ToList());
+        }
+
+        public static UntypedObjectValue New(UntypedObjectBase untypedObject)
+        {
+            return new UntypedObjectValue(
+                IRContext.NotInSource(new UntypedObjectType()),
+                untypedObject);
         }
 
         public static UntypedObjectValue New(IUntypedObject untypedObject)

src/libraries/Microsoft.PowerFx.Core/Public/Values/UntypedObjectValue.cs

@@ -79,5 +79,39 @@ namespace Microsoft.PowerFx.Types
             // Not supported for the time being.
             throw new NotImplementedException("UntypedObjectValue cannot be serialized.");
         }
-    }
+    }
+
+    public abstract class UntypedObjectBase : IUntypedObject
+    {
+        public abstract IUntypedObject this[int index] { get; }
+
+        public abstract FormulaType Type { get; }
+
+        public abstract int GetArrayLength();
+
+        public abstract bool GetBoolean();
+
+        public abstract decimal GetDecimal();
+
+        public abstract double GetDouble();
+
+        public abstract string GetString();
+
+        public abstract string GetUntypedNumber();
+
+        public abstract bool TryGetProperty(string value, out IUntypedObject result);
+
+        public abstract bool TryGetPropertyNames(out IEnumerable<string> propertyNames);
+
+        /// <summary>
+        /// Set a property on the object.
+        /// </summary>
+        /// <param name="propertyName">Property name.</param>
+        /// <param name="value">FormulaValue to be set.</param>
+        public virtual void SetProperty(string propertyName, FormulaValue value)
+        {
+            // In case of unwanted behavior, throw an CustomFunctionErrorException exception.
+            throw new NotImplementedException();
+        }
+    }
 }

src/libraries/Microsoft.PowerFx.Core/Texl/Builtins/UntypedObject.cs

@@ -1,9 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 
-using System;
 using System.Collections.Generic;
-using System.Text;
 using Microsoft.PowerFx.Core.Functions;
 using Microsoft.PowerFx.Core.Localization;
 using Microsoft.PowerFx.Core.Types;
@@ -35,6 +33,8 @@ namespace Microsoft.PowerFx.Core.Texl.Builtins
 
         public override bool IsSelfContained => true;
 
+        public override bool PropagatesMutability => true;
+
         public IndexFunction_UO()
             : base(IndexInvariantFunctionName, TexlStrings.AboutIndex, FunctionCategories.Table, DType.UntypedObject, 0, 2, 2, DType.UntypedObject, DType.Number)
         {

src/libraries/Microsoft.PowerFx.Interpreter/EvalVisitor.cs

@@ -19,6 +19,7 @@ using Microsoft.PowerFx.Interpreter;
 using Microsoft.PowerFx.Interpreter.Exceptions;
 using Microsoft.PowerFx.Types;
 using static Microsoft.PowerFx.Functions.Library;
+using static Microsoft.PowerFx.Syntax.PrettyPrintVisitor;
 
 namespace Microsoft.PowerFx
 {
@@ -154,28 +155,58 @@ namespace Microsoft.PowerFx
         // Set is unique because it has an l-value for the first arg. 
         // Async params can't have out-params. 
         // Return null if not handled. Else non-null if handled.
-        private async Task<FormulaValue> TryHandleSet(CallNode node, EvalVisitorContext context)
-        {
-            // Special case Set() calls because they take an LValue. 
-            if (node.Function.GetType() != typeof(RecalcEngineSetFunction))
-            {
-                return null;
-            }
-
-            var arg0 = node.Args[0];
-            var arg1 = node.Args[1];
-
+        private async Task<FormulaValue> TryHandleSet(CallNode node, EvalVisitorContext context)
+        {
+            // Special case Set() calls because they take an LValue. 
+            if (node.Function.GetType() != typeof(RecalcEngineSetFunction))
+            {
+                return null;
+            }
+
+            var arg0 = node.Args[0];
+            var arg1 = node.Args[1];
+
             var newValue = await arg1.Accept(this, context).ConfigureAwait(false);
 
-            if (arg0.IRContext.IsMutation && arg0 is RecordFieldAccessNode rfan)
+            if (arg0.IRContext.IsMutation)
             {
-                var arg0value = await rfan.From.Accept(this, context).ConfigureAwait(false);
-                
-                if (arg0value is RecordValue rv)
+                if (arg0 is RecordFieldAccessNode rfan)
                 {
-                    rv.ShallowCopyFieldInPlace(rfan.Field);
-                    rv.UpdateField(rfan.Field, newValue);
-                    return node.IRContext.ResultType._type.Kind == DKind.Boolean ? FormulaValue.New(true) : FormulaValue.NewVoid();
+                    var arg0value = await rfan.From.Accept(this, context).ConfigureAwait(false);
+
+                    if (arg0value is RecordValue rv)
+                    {
+                        rv.ShallowCopyFieldInPlace(rfan.Field);
+                        rv.UpdateField(rfan.Field, newValue);
+                        return node.IRContext.ResultType._type.Kind == DKind.Boolean ? FormulaValue.New(true) : FormulaValue.NewVoid();
+                    }
+                    else
+                    {
+                        return CommonErrors.UnreachableCodeError(node.IRContext);
+                    }
+                }
+                else if (arg0 is BinaryOpNode bon && bon.Op == BinaryOpKind.DynamicGetField)
+                {
+                    var arg0value = await bon.Left.Accept(this, context).ConfigureAwait(false);
+
+                    if (arg0value is UntypedObjectValue uov && uov.Impl is UntypedObjectBase impl)
+                    {
+                        TextLiteralNode textLiteralNode = (TextLiteralNode)bon.Right;
+
+                        try
+                        {
+                            impl.SetProperty(textLiteralNode.LiteralValue, newValue);
+                            return node.IRContext.ResultType._type.Kind == DKind.Boolean ? FormulaValue.New(true) : FormulaValue.NewVoid();
+                        }
+                        catch (CustomFunctionErrorException ex)
+                        {
+                            return new ErrorValue(node.IRContext, new ExpressionError() { Message = ex.Message, Span = node.IRContext.SourceContext, Kind = ex.ErrorKind });
+                        }
+                        catch (NotImplementedException)
+                        {
+                            return CommonErrors.NotYetImplementedError(node.IRContext, $"Class {impl.GetType()} does not implement 'SetProperty'.");
+                        }
+                    }
                 }
                 else
                 {
@@ -184,9 +215,9 @@ namespace Microsoft.PowerFx
             }
 
             // Binder has already ensured this is a first name node as well as mutable symbol. 
-            if (arg0 is ResolvedObjectNode obj)
-            {
-                if (obj.Value is ISymbolSlot sym)
+            if (arg0 is ResolvedObjectNode obj)
+            {
+                if (obj.Value is ISymbolSlot sym)
                 {
                     if (_symbolValues != null)
                     {
@@ -197,9 +228,9 @@ namespace Microsoft.PowerFx
                     // This may happen if the runtime symbols are missing a value and we failed to update. 
                 }
             }
-
-            // Fail?
-            return CommonErrors.UnreachableCodeError(node.IRContext);
+
+            // Fail?
+            return CommonErrors.UnreachableCodeError(node.IRContext);
         }
 
         // Handle invoke SetProperty(source.Prop, newValue)

src/libraries/Microsoft.PowerFx.Interpreter/Functions/SetFunction.cs

@@ -55,6 +55,12 @@ namespace Microsoft.PowerFx.Interpreter
             nodeToCoercedTypeMap = null;
             returnType = context.Features.PowerFxV1CompatibilityRules ? DType.Void : DType.Boolean;
 
+            if (argTypes[0].IsUntypedObject)
+            {
+                // if arg0 is untyped object, the host implementation will handle arg1.
+                return true;
+            }
+
             var isValid = CheckType(context, args[1], argTypes[1], argTypes[0], errors, ref nodeToCoercedTypeMap);
 
             return isValid;
@@ -64,43 +70,63 @@ namespace Microsoft.PowerFx.Interpreter
         public override void CheckSemantics(TexlBinding binding, TexlNode[] args, DType[] argTypes, IErrorContainer errors)
         {
             base.CheckSemantics(binding, args, argTypes, errors);
-
-            Contracts.AssertValue(args);
-            Contracts.AssertAllValues(args);
-            Contracts.AssertValue(argTypes);
-            Contracts.AssertAllValid(argTypes);
-            Contracts.Assert(args.Length == argTypes.Length);
-            Contracts.AssertValue(errors);
-            Contracts.Assert(MinArity <= args.Length && args.Length <= MaxArity);
-
+
+            Contracts.AssertValue(args);
+            Contracts.AssertAllValues(args);
+            Contracts.AssertValue(argTypes);
+            Contracts.AssertAllValid(argTypes);
+            Contracts.Assert(args.Length == argTypes.Length);
+            Contracts.AssertValue(errors);
+            Contracts.Assert(MinArity <= args.Length && args.Length <= MaxArity);
+
             var arg0 = argTypes[0];
             var arg1 = argTypes[1];
 
             // Type check
-            if (!(arg0.Accepts(arg1, exact: true, useLegacyDateTimeAccepts: false, usePowerFxV1CompatibilityRules: binding.Features.PowerFxV1CompatibilityRules) ||
-                 (arg0.IsNumeric && arg1.IsNumeric)))
+            if (arg0.IsUntypedObject)
             {
-                errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrBadType_ExpectedType_ProvidedType, arg0.GetKindString(), arg1.GetKindString());
-                return;
+                if (CheckMutability(binding, args, argTypes, errors))
+                {
+                    return;
+                }
+            }
+            else
+            {
+                if (!(arg0.Accepts(arg1, exact: true, useLegacyDateTimeAccepts: false, usePowerFxV1CompatibilityRules: binding.Features.PowerFxV1CompatibilityRules) ||
+                 (arg0.IsNumeric && arg1.IsNumeric)))
+                {
+                    errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrBadType_ExpectedType_ProvidedType, arg0.GetKindString(), arg1.GetKindString());
+                    return;
+                }
+
+                if (arg1.AggregateHasExpandedType())
+                {
+                    if (arg1.IsTable)
+                    {
+                        errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrSetVariableWithRelationshipNotAllowTable);
+                        return;
+                    }
+
+                    if (arg1.IsRecord)
+                    {
+                        errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrSetVariableWithRelationshipNotAllowRecord);
+                        return;
+                    }
+                }
+
+                if (CheckMutability(binding, args, argTypes, errors))
+                {
+                    return;
+                }
             }
 
-            if (arg1.AggregateHasExpandedType())
-            {
-                if (arg1.IsTable)
-                {
-                    errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrSetVariableWithRelationshipNotAllowTable);
-                    return;
-                }
-
-                if (arg1.IsRecord)
-                {
-                    errors.EnsureError(DocumentErrorSeverity.Critical, args[1], ErrSetVariableWithRelationshipNotAllowRecord);
-                    return;
-                }
-            }
-
-            var firstName = args[0].AsFirstName();
+            errors.EnsureError(DocumentErrorSeverity.Severe, args[0], TexlStrings.ErrNeedValidVariableName_Arg, Name, args[0]);
+            return;
+        }
 
+        private bool CheckMutability(TexlBinding binding, TexlNode[] args, DType[] argTypes, IErrorContainer errors)
+        {
+            var firstName = args[0].AsFirstName();
             if (firstName != null)
             {
                 // Variable reference assignment, for example Set( x, 3 )
@@ -108,18 +134,17 @@ namespace Microsoft.PowerFx.Interpreter
                 if (info.Data is NameSymbol nameSymbol && nameSymbol.Props.CanSet)
                 {
                     // We have a variable, success
-                    return;
+                    return true;
                 }
             }
             else if (binding.Features.PowerFxV1CompatibilityRules)
             {
                 // Deep mutation, for example Set( x.a, 4 )
                 base.ValidateArgumentIsSetMutable(binding, args[0], errors);
-                return;
+                return true;
             }
 
-            errors.EnsureError(DocumentErrorSeverity.Severe, args[0], TexlStrings.ErrNeedValidVariableName_Arg, Name, args[0]);
-            return;
+            return false;
         }
     }
 }

src/libraries/Microsoft.PowerFx.Json/Functions/JsonUntypedObject.cs

@@ -9,27 +9,27 @@ using Microsoft.PowerFx.Types;
 
 namespace Microsoft.PowerFx.Functions
 {
-    internal class JsonUntypedObject : IUntypedObject
-    {
-        internal readonly JsonElement _element;
-
-        public JsonUntypedObject(JsonElement element)
-        {
-            _element = element;
-        }
-
-        public FormulaType Type
-        {
-            get
-            {
-                switch (_element.ValueKind)
-                {
-                    case JsonValueKind.Object:
-                        return ExternalType.ObjectType;
-                    case JsonValueKind.Array:
-                        return ExternalType.ArrayType;
-                    case JsonValueKind.String:
-                        return FormulaType.String;
+    internal class JsonUntypedObject : UntypedObjectBase
+    {
+        internal readonly JsonElement _element;
+
+        public JsonUntypedObject(JsonElement element)
+        {
+            _element = element;
+        }
+
+        public override FormulaType Type
+        {
+            get
+            {
+                switch (_element.ValueKind)
+                {
+                    case JsonValueKind.Object:
+                        return ExternalType.ObjectType;
+                    case JsonValueKind.Array:
+                        return ExternalType.ArrayType;
+                    case JsonValueKind.String:
+                        return FormulaType.String;
                     case JsonValueKind.Number:
                         // Do not be tempted to use FormulaType.Number here.  JSON numbers can be interpreted as either
                         // a float or a decimal and connectors take advantage of this to interop with decimals in databases.
@@ -41,45 +41,45 @@ namespace Microsoft.PowerFx.Functions
                         // number types of various capacities and complements, fixed or floating, binary or decimal.That can make
                         // interchange between different programming languages difficult. JSON instead offers only the representation of
                         // numbers that humans use: a sequence of digits. All programming languages know how to make sense of digit
-                        // sequences even if they disagree on internal representations. That is enough to allow interchange 
+                        // sequences even if they disagree on internal representations. That is enough to allow interchange 
                         return ExternalType.UntypedNumber;
-                    case JsonValueKind.True:
-                    case JsonValueKind.False:
-                        return FormulaType.Boolean;
-                }
-
-                return FormulaType.Blank;
-            }
-        }
-
-        public IUntypedObject this[int index] => new JsonUntypedObject(_element[index]);
-
-        public int GetArrayLength()
-        {
-            return _element.GetArrayLength();
-        }
-
-        public double GetDouble()
-        {
-            return _element.GetDouble();
-        }
-
-        public string GetString()
-        {
-            return _element.GetString();
-        }
-
-        public bool GetBoolean()
-        {
-            return _element.GetBoolean();
+                    case JsonValueKind.True:
+                    case JsonValueKind.False:
+                        return FormulaType.Boolean;
+                }
+
+                return FormulaType.Blank;
+            }
         }
 
-        public decimal GetDecimal()
+        public override IUntypedObject this[int index] => new JsonUntypedObject(_element[index]);
+
+        public override int GetArrayLength()
+        {
+            return _element.GetArrayLength();
+        }
+
+        public override double GetDouble()
+        {
+            return _element.GetDouble();
+        }
+
+        public override string GetString()
+        {
+            return _element.GetString();
+        }
+
+        public override bool GetBoolean()
+        {
+            return _element.GetBoolean();
+        }
+
+        public override decimal GetDecimal()
         {
             return _element.GetDecimal();
         }
 
-        public string GetUntypedNumber()
+        public override string GetUntypedNumber()
         {
             if (Type == ExternalType.UntypedNumber)
             {
@@ -89,25 +89,25 @@ namespace Microsoft.PowerFx.Functions
             {
                 throw new FormatException();
             }
-        }
-
-        public bool TryGetProperty(string value, out IUntypedObject result)
-        {
-            var res = _element.TryGetProperty(value, out var je);
-            result = new JsonUntypedObject(je);
-            return res;
         }
 
-        public bool TryGetPropertyNames(out IEnumerable<string> result)
+        public override bool TryGetProperty(string value, out IUntypedObject result)
+        {
+            var res = _element.TryGetProperty(value, out var je);
+            result = new JsonUntypedObject(je);
+            return res;
+        }
+
+        public override bool TryGetPropertyNames(out IEnumerable<string> result)
         {
             if (_element.ValueKind != JsonValueKind.Object)
             {
                 result = null;
                 return false;
             }
-             
+
             result = _element.EnumerateObject().Select(x => x.Name);
             return true;
-        }
+        }
     }
 }

src/tests/Microsoft.PowerFx.Core.Tests.Shared/PublicSurfaceTests.cs

@@ -141,6 +141,7 @@ namespace Microsoft.PowerFx.Core.Tests
                 "Microsoft.PowerFx.Types.IDelegatableTableValue",
                 "Microsoft.PowerFx.Types.ITypeVisitor",
                 "Microsoft.PowerFx.Types.IUntypedObject",
+                "Microsoft.PowerFx.Types.UntypedObjectBase",
                 "Microsoft.PowerFx.Types.IValueVisitor",              
                 "Microsoft.PowerFx.Types.NamedFormulaType",
                 "Microsoft.PowerFx.Types.NamedValue",

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/DateTimeUTCTests.cs

@@ -294,7 +294,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             }
         }
 
-        private class SimpleObject : IUntypedObject
+        private class SimpleObject : UntypedObjectBase
         {
             private readonly FormulaValue _value;
 
@@ -303,46 +303,46 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                 _value = value;
             }
 
-            public IUntypedObject this[int index] => throw new NotImplementedException();
+            public override IUntypedObject this[int index] => throw new NotImplementedException();
 
-            public FormulaType Type => _value.Type;
+            public override FormulaType Type => _value.Type;
 
-            public int GetArrayLength()
+            public override int GetArrayLength()
             {
                 throw new NotImplementedException();
             }
 
-            public bool GetBoolean()
+            public override bool GetBoolean()
             {
                 return ((BooleanValue)_value).Value;
             }
 
-            public double GetDouble()
+            public override double GetDouble()
             {
                 return ((NumberValue)_value).Value;
             }
 
-            public decimal GetDecimal()
+            public override decimal GetDecimal()
             {
                 return ((DecimalValue)_value).Value;
             }
 
-            public string GetUntypedNumber()
+            public override string GetUntypedNumber()
             {
                 return ((StringValue)_value).Value;
             }
 
-            public string GetString()
+            public override string GetString()
             {
                 return ((StringValue)_value).Value;
             }
 
-            public bool TryGetProperty(string value, out IUntypedObject result)
+            public override bool TryGetProperty(string value, out IUntypedObject result)
             {
                 throw new NotImplementedException();
             }
 
-            public bool TryGetPropertyNames(out IEnumerable<string> result)
+            public override bool TryGetPropertyNames(out IEnumerable<string> result)
             {
                 result = null;
                 return false;

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/MutationScripts/Set_DeepMutation_V1Compat.txt

@@ -339,4 +339,8 @@ Errors: Error 45-52: The value passed to the 'Set' function cannot be changed.
 >> rwt1_copy3
 {Field1:3,Field2:{Field2_1:321,Field2_2:"2_2",Field2_4:Table({Field1:1,Field2:"earth",Field3:DateTime(2022,1,1,0,0,0,0),Field4:true})}}
 
+// Untyped object
+>> IsError(Set(ParseJSON("{""x"":5}").x, 99))
+Errors: Error 34-36: The value passed to the 'Set' function cannot be changed.
+
 

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/PadUntypedObjectTests.cs

@@ -45,9 +45,59 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             Assert.Equal(FormulaType.UntypedObject, fv3.Type);
             Assert.True(fv3 is BlankValue);
         }
+
+        [Fact]
+        public void PadUntypedObjectMutationTest()
+        {
+            DataTable dt = new DataTable("someTable");
+            dt.Columns.Add("Id", typeof(int));
+            dt.Columns.Add("Column1", typeof(string));
+            dt.Columns.Add("Column2", typeof(string));
+            dt.Rows.Add(1, "data1", "data2");
+            dt.Rows.Add(2, "data3", "data4");
+
+            PadUntypedObject uo = new PadUntypedObject(dt);
+            PadUntypedObject uoCell = new PadUntypedObject(99);
+            NotImplementedUntypedObject notImplementedUO = new NotImplementedUntypedObject(dt);
+
+            UntypedObjectValue uov = new UntypedObjectValue(IRContext.NotInSource(FormulaType.UntypedObject), uo);
+            UntypedObjectValue uovCell = new UntypedObjectValue(IRContext.NotInSource(FormulaType.UntypedObject), uoCell);
+            UntypedObjectValue notImplementedValue = new UntypedObjectValue(IRContext.NotInSource(FormulaType.UntypedObject), notImplementedUO);
+
+            PowerFxConfig config = new PowerFxConfig(Features.PowerFxV1);
+            RecalcEngine engine = new RecalcEngine(config);
+
+            engine.Config.SymbolTable.EnableMutationFunctions();
+            engine.UpdateVariable("padTable", uov, new SymbolProperties() { CanMutate = true, CanSetMutate = true });
+            engine.UpdateVariable("notImplementedUO", notImplementedValue, new SymbolProperties() { CanMutate = true, CanSetMutate = true });
+            engine.UpdateVariable("padCell", uovCell);
+
+            // Setting an untyped object (padCell).
+            DecimalValue result = (DecimalValue)engine.Eval(@"Set(Index(padTable, 1).Id, padCell);Index(padTable, 1).Id+1", options: new ParserOptions() { AllowsSideEffects = true });
+            Assert.Equal(100m, result.ToObject());
+
+            // Setting a strongly typed object (99).
+            result = (DecimalValue)engine.Eval(@"Set(Index(padTable, 1).Id, 99);Index(padTable, 1).Id+1", options: new ParserOptions() { AllowsSideEffects = true });
+            Assert.Equal(100m, result.ToObject());
+
+            // Property does not exist.
+            ErrorValue errorValue = (ErrorValue)engine.Eval(@"Set(Index(padTable, 1).DoesNotExist, 99)", options: new ParserOptions() { AllowsSideEffects = true });
+            Assert.IsType<ErrorValue>(errorValue);
+            Assert.Equal(ErrorKind.InvalidArgument, errorValue.Errors.First().Kind);
+
+            // Type not supported.
+            errorValue = (ErrorValue)engine.Eval(@"Set(Index(padTable, 1).Column2, GUID())", options: new ParserOptions() { AllowsSideEffects = true });
+            Assert.IsType<ErrorValue>(errorValue);
+            Assert.Equal(ErrorKind.InvalidArgument, errorValue.Errors.First().Kind);
+
+            // 'SetProperty' not implemented.
+            errorValue = (ErrorValue)engine.Eval(@"Set(Index(notImplementedUO, 1).Id, 1)", options: new ParserOptions() { AllowsSideEffects = true });
+            Assert.IsType<ErrorValue>(errorValue);
+            Assert.Equal(ErrorKind.NotSupported, errorValue.Errors.First().Kind);
+        }
     }
 
-    public class PadUntypedObject : IUntypedObject
+    public class PadUntypedObject : UntypedObjectBase
     {
         public DataTable DataTable;
         public DataRow DataRow;
@@ -74,8 +124,6 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             Cell = cell;
         }
 
-        public IUntypedObject this[int index] => Index(index);
-
         private IUntypedObject Index(int index)
         {
             return (DataTable != null)
@@ -85,7 +133,9 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                     : throw new NotImplementedException();
         }
 
-        public FormulaType Type => GetFormulaType();
+        public override FormulaType Type => GetFormulaType();
+
+        public override IUntypedObject this[int index] => Index(index);
 
         private FormulaType GetFormulaType()
         {
@@ -102,7 +152,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                 : ExternalType.ArrayAndObject;
         }
 
-        public int GetArrayLength()
+        public override int GetArrayLength()
         {
             return (DataTable != null)
                  ? DataTable.Rows.Count
@@ -111,12 +161,12 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                  : throw new NotImplementedException();
         }
 
-        public bool GetBoolean()
+        public override bool GetBoolean()
         {
             throw new NotImplementedException();
         }
 
-        public double GetDouble()
+        public override double GetDouble()
         {
             return Cell switch
             {
@@ -127,12 +177,12 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             };
         }
 
-        public decimal GetDecimal()
+        public override decimal GetDecimal()
         {
             throw new NotImplementedException();
         }
 
-        public string GetUntypedNumber()
+        public override string GetUntypedNumber()
         {
             throw new NotImplementedException();
         }
@@ -142,12 +192,12 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             throw new NotImplementedException();
         }
 
-        public string GetString()
+        public override string GetString()
         {
             return Cell.ToString();
         }
 
-        public bool TryGetProperty(string propertyName, out IUntypedObject result)
+        public override bool TryGetProperty(string propertyName, out IUntypedObject result)
         {
             if (DataTable != null)
             {
@@ -165,7 +215,154 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             return true;
         }
 
-        public bool TryGetPropertyNames(out IEnumerable<string> result)
+        public override bool TryGetPropertyNames(out IEnumerable<string> result)
+        {
+            result = null;
+            return false;
+        }
+
+        public override void SetProperty(string propertyName, FormulaValue value)
+        {
+            if (DataTable != null)
+            {
+                throw new NotImplementedException();
+            }
+
+            if (!DataRow.Table.Columns.Contains(propertyName))
+            {
+                value = default;
+                throw new CustomFunctionErrorException($"Property '{propertyName}' does not exist.", ErrorKind.InvalidArgument);
+            }
+
+            if (value is DecimalValue dv)
+            {
+                DataRow[propertyName] = dv.Value;
+            }
+            else if (value is GuidValue)
+            {
+                throw new CustomFunctionErrorException($"Type '{value.Type.ToString()}' is not supported.", ErrorKind.InvalidArgument);
+            }
+            else if (value is UntypedObjectValue uov)
+            {
+                if (DataRow[propertyName].GetType() == typeof(string))
+                {
+                    DataRow[propertyName] = uov.Impl.GetString();
+                }
+                else if (DataRow[propertyName].GetType() == typeof(int))
+                {
+                    DataRow[propertyName] = uov.Impl.GetDouble();
+                }
+                else if (DataRow[propertyName].GetType() == typeof(bool))
+                {
+                    DataRow[propertyName] = uov.Impl.GetBoolean();
+                }
+                else if (DataRow[propertyName].GetType() == typeof(decimal))
+                {
+                    DataRow[propertyName] = uov.Impl.GetDecimal();
+                }
+                else
+                {
+                    throw new CustomFunctionErrorException($"Type '{DataRow[propertyName].GetType()}' is not supported.", ErrorKind.InvalidArgument);
+                }
+            }
+        }
+    }
+
+    public class NotImplementedUntypedObject : UntypedObjectBase
+    {
+        public DataTable DataTable;
+        public DataRow DataRow;
+        public object Cell;
+
+        public NotImplementedUntypedObject(DataTable dt)
+        {
+            DataTable = dt;
+            DataRow = null;
+            Cell = null;
+        }
+
+        public NotImplementedUntypedObject(DataRow dr)
+        {
+            DataTable = null;
+            DataRow = dr;
+            Cell = null;
+        }
+
+        public NotImplementedUntypedObject(object cell)
+        {
+            DataTable = null;
+            DataRow = null;
+            Cell = cell;
+        }
+
+        private IUntypedObject Index(int index)
+        {
+            return new NotImplementedUntypedObject(DataTable.Rows[index]);
+        }
+
+        public override FormulaType Type => GetFormulaType();
+
+        public override IUntypedObject this[int index] => Index(index);
+
+        private FormulaType GetFormulaType()
+        {
+            return ExternalType.ArrayAndObject;
+        }
+
+        public override int GetArrayLength()
+        {
+            return 1;
+        }
+
+        public override bool GetBoolean()
+        {
+            throw new NotImplementedException();
+        }
+
+        public override double GetDouble()
+        {
+            throw new NotImplementedException();
+        }
+
+        public override decimal GetDecimal()
+        {
+            throw new NotImplementedException();
+        }
+
+        public override string GetUntypedNumber()
+        {
+            throw new NotImplementedException();
+        }
+
+        public string[] GetPropertyNames()
+        {
+            throw new NotImplementedException();
+        }
+
+        public override string GetString()
+        {
+            return Cell.ToString();
+        }
+
+        public override bool TryGetProperty(string propertyName, out IUntypedObject result)
+        {
+            if (DataTable != null)
+            {
+                throw new NotImplementedException();
+            }
+
+            if (!DataRow.Table.Columns.Contains(propertyName))
+            {
+                result = default;
+                return false;
+            }
+
+            var cell = DataRow[propertyName];
+            result = new NotImplementedUntypedObject(cell);
+            return true;
+        }
+
+        public override bool TryGetPropertyNames(out IEnumerable<string> result)
         {
             result = null;
             return false;

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/PowerFxEvaluationTests.cs

@@ -799,6 +799,8 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             var t_bsType = TableType.Empty().Add("b", FormulaType.String);
             engine.UpdateVariable("t_bs1", FormulaValue.NewTable(t_bsType.ToRecord()));
             engine.UpdateVariable("t_bs2", FormulaValue.NewTable(t_bsType.ToRecord()));
+
+            engine.Config.EnableJsonFunctions();
         }        
 
         private static void TraceSetup(RecalcEngine engine, bool numberIsFloat)

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/Scenarios/PrimitiveWrapperAsUnknownObject.cs

@@ -14,7 +14,8 @@ namespace Microsoft.PowerFx.Tests
     // Wrap a .net object as an UntypedObject.
     // This will lazily marshal through the object as it's accessed.
     [DebuggerDisplay("{_source}")]
-    public class PrimitiveWrapperAsUnknownObject : IUntypedObject
+    [DebuggerDisplay("{_source}")]
+    public class PrimitiveWrapperAsUnknownObject : UntypedObjectBase
     {
         public readonly object _source;
 
@@ -28,7 +29,7 @@ namespace Microsoft.PowerFx.Tests
             return FormulaValue.New(new PrimitiveWrapperAsUnknownObject(source));
         }
 
-        public FormulaType Type
+        public override FormulaType Type
         {
             get
             {
@@ -61,7 +62,7 @@ namespace Microsoft.PowerFx.Tests
             }
         }
 
-        public IUntypedObject this[int index]
+        public override IUntypedObject this[int index]
         {
             get
             {
@@ -81,13 +82,13 @@ namespace Microsoft.PowerFx.Tests
             }
         }
 
-        public int GetArrayLength()
+        public override int GetArrayLength()
         {
             var a = (Array)_source;
             return a.Length;
         }
 
-        public bool GetBoolean()
+        public override bool GetBoolean()
         {
             Assert.True(Type == FormulaType.Boolean);
 
@@ -99,7 +100,7 @@ namespace Microsoft.PowerFx.Tests
             throw new InvalidOperationException($"Not a boolean type");
         }
 
-        public double GetDouble()
+        public override double GetDouble()
         {
             // Fx will only call this helper for numbers. 
             Assert.True(Type == FormulaType.Number);
@@ -122,7 +123,7 @@ namespace Microsoft.PowerFx.Tests
             throw new InvalidOperationException($"Not a number type");
         }
 
-        public decimal GetDecimal()
+        public override decimal GetDecimal()
         {
             // Fx will only call this helper for decimals. 
             Assert.True(Type == FormulaType.Decimal);
@@ -145,12 +146,12 @@ namespace Microsoft.PowerFx.Tests
             throw new InvalidOperationException($"Not a decimal type");
         }
 
-        public string GetUntypedNumber()
+        public override string GetUntypedNumber()
         {
             throw new NotImplementedException();
         }
 
-        public string GetString()
+        public override string GetString()
         {
             Assert.True(Type == FormulaType.String);
 
@@ -162,7 +163,7 @@ namespace Microsoft.PowerFx.Tests
             throw new InvalidOperationException($"Not a string type");
         }
 
-        public bool TryGetProperty(string value, out IUntypedObject result)
+        public override bool TryGetProperty(string value, out IUntypedObject result)
         {
             Assert.True(Type == ExternalType.ObjectType);
 
@@ -191,7 +192,7 @@ namespace Microsoft.PowerFx.Tests
             return true;
         }
 
-        public bool TryGetPropertyNames(out IEnumerable<string> result)
+        public override bool TryGetPropertyNames(out IEnumerable<string> result)
         {
             result = null;
             return false;

src/tests/Microsoft.PowerFx.Interpreter.Tests.Shared/Scenarios/ScenarioMutation.cs

@@ -13,7 +13,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
 {
     // Demonstrate mutation example using IUntypedObject
     public class ScenarioMutation : PowerFxTest
-    {       
+    {
         [Fact]
         public void MutabilityTest()
         {
@@ -26,7 +26,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             {
                 ["prop"] = FormulaValue.New(123)
             };
-                        
+
             var obj = MutableObject.New(d);
             engine.UpdateVariable("obj", obj);
 
@@ -45,15 +45,15 @@ namespace Microsoft.PowerFx.Interpreter.Tests
 
         [Theory]
         [InlineData("Assert2(obj.prop, 123); Set2(obj, \"prop\", 456); Assert2(obj.prop, 456)")]
-        [InlineData("Assert2(obj.prop, 123); Set3(obj, \"prop\", \"prop2\"); Assert2(obj.prop, 456)")]       
+        [InlineData("Assert2(obj.prop, 123); Set3(obj, \"prop\", \"prop2\"); Assert2(obj.prop, 456)")]
         public void MutabilityTest_Chain(string expr)
         {
-            var config = new PowerFxConfig();            
+            var config = new PowerFxConfig();
             config.AddFunction(new Assert2Function());
             config.AddFunction(new Set2Function());
             config.AddFunction(new Set3Function());
-            var engine = new RecalcEngine(config);            
-                      
+            var engine = new RecalcEngine(config);
+
             var d = new Dictionary<string, FormulaValue>
             {
                 ["prop"] = FormulaValue.New(123),
@@ -72,7 +72,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
 
             Assert.IsType<DecimalValue>(x);
             Assert.Equal(456, ((DecimalValue)x).Value);
-            Assert.Equal(456, ((DecimalValue)d["prop"]).Value);                      
+            Assert.Equal(456, ((DecimalValue)d["prop"]).Value);
         }
 
         [Fact]
@@ -133,7 +133,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             {
                 var impl = (MutableObject)obj.Impl;
                 impl.TryGetProperty(propName2.Value, out var propValue);
-                var val = propValue.GetDecimal();                
+                var val = propValue.GetDecimal();
                 impl.Set(propName.Value, new DecimalValue(IRContext.NotInSource(FormulaType.Decimal), val));
             }
         }
@@ -193,7 +193,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
             }
         }
 
-        private class MutableObject : IUntypedObject
+        private class MutableObject : UntypedObjectBase
         {
             private Dictionary<string, FormulaValue> _values = new Dictionary<string, FormulaValue>();
 
@@ -212,41 +212,41 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                 return FormulaValue.New(x);
             }
 
-            public IUntypedObject this[int index] => throw new NotImplementedException();
+            public override IUntypedObject this[int index] => throw new NotImplementedException();
 
-            public FormulaType Type => ExternalType.ObjectType;
+            public override FormulaType Type => ExternalType.ObjectType;
 
-            public int GetArrayLength()
+            public override int GetArrayLength()
             {
                 throw new NotImplementedException();
             }
 
-            public bool GetBoolean()
+            public override bool GetBoolean()
             {
                 throw new NotImplementedException();
             }
 
-            public double GetDouble()
-            {
-                throw new NotImplementedException();
-            }
-            
-            public decimal GetDecimal()
+            public override double GetDouble()
             {
                 throw new NotImplementedException();
             }
 
-            public string GetUntypedNumber()
+            public override decimal GetDecimal()
             {
                 throw new NotImplementedException();
             }
 
-            public string GetString()
+            public override string GetUntypedNumber()
             {
                 throw new NotImplementedException();
             }
 
-            public bool TryGetProperty(string value, out IUntypedObject result)
+            public override string GetString()
+            {
+                throw new NotImplementedException();
+            }
+
+            public override bool TryGetProperty(string value, out IUntypedObject result)
             {
                 if (_values.TryGetValue(value, out var x))
                 {
@@ -258,7 +258,7 @@ namespace Microsoft.PowerFx.Interpreter.Tests
                 return false;
             }
 
-            public bool TryGetPropertyNames(out IEnumerable<string> result)
+            public override bool TryGetPropertyNames(out IEnumerable<string> result)
             {
                 result = null;
                 return false;