IsEmpty supports UO (#2672)

Issue https://github.com/microsoft/Power-Fx/issues/2671.
Still need to verify other functions.

src/libraries/Microsoft.PowerFx.Core/Texl/BuiltinFunctionsCore.cs

@@ -127,7 +127,8 @@ namespace Microsoft.PowerFx.Core.Texl
         public static readonly TexlFunction IsBlankOptionSetValue = _library.Add(new IsBlankOptionSetValueFunction());
         public static readonly TexlFunction IsBlankOrError = _library.Add(new IsBlankOrErrorFunction());
         public static readonly TexlFunction IsBlankOrErrorOptionSetValue = _library.Add(new IsBlankOrErrorOptionSetValueFunction());
-        public static readonly TexlFunction IsEmpty = _library.Add(new IsEmptyFunction());
+        public static readonly TexlFunction IsEmpty = _library.Add(new IsEmptyFunction());
+        public static readonly TexlFunction IsEmpty_UO = _library.Add(new IsEmptyFunction_UO());
         public static readonly TexlFunction IsError = _library.Add(new IsErrorFunction());
         public static readonly TexlFunction IsNumeric = _library.Add(new IsNumericFunction());
         public static readonly TexlFunction ISOWeekNum = _library.Add(new ISOWeekNumFunction());
@@ -253,7 +254,7 @@ namespace Microsoft.PowerFx.Core.Texl
         public static readonly TexlFunction Decimal = _featureGateFunctions.Add(new DecimalFunction());
         public static readonly TexlFunction Decimal_UO = _featureGateFunctions.Add(new DecimalFunction_UO());
         public static readonly TexlFunction Float = _featureGateFunctions.Add(new FloatFunction());
-        public static readonly TexlFunction Float_UO = _featureGateFunctions.Add(new FloatFunction_UO());
+        public static readonly TexlFunction Float_UO = _featureGateFunctions.Add(new FloatFunction_UO());
         public static readonly TexlFunction IsUTCToday = _featureGateFunctions.Add(new IsUTCTodayFunction());
         public static readonly TexlFunction UTCNow = _featureGateFunctions.Add(new UTCNowFunction());
         public static readonly TexlFunction UTCToday = _featureGateFunctions.Add(new UTCTodayFunction());

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

@@ -68,4 +68,19 @@ namespace Microsoft.PowerFx.Core.Texl.Builtins
             return fValid;
         }
     }
+
+    internal sealed class IsEmptyFunction_UO : BuiltinFunction
+    {
+        public override bool IsSelfContained => true;
+
+        public IsEmptyFunction_UO()
+            : base("IsEmpty", TexlStrings.AboutIsEmpty, FunctionCategories.Table | FunctionCategories.Information, DType.Boolean, 0, 1, 1, DType.UntypedObject)
+        {
+        }
+
+        public override IEnumerable<TexlStrings.StringGetter[]> GetSignatures()
+        {
+            yield return new[] { TexlStrings.IsEmptyArg1 };
+        }
+    }
 }

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

@@ -982,6 +982,17 @@ namespace Microsoft.PowerFx.Functions
                     returnBehavior: ReturnBehavior.AlwaysEvaluateAndReturnResult,
                     targetFunction: IsEmpty)
             },
+            {
+                BuiltinFunctionsCore.IsEmpty_UO,
+                StandardErrorHandling<UntypedObjectValue>(
+                    BuiltinFunctionsCore.IsEmpty_UO.Name,
+                    expandArguments: NoArgExpansion,
+                    replaceBlankValues: DoNotReplaceBlank,
+                    checkRuntimeTypes: ExactValueTypeOrBlank<UntypedObjectValue>,
+                    checkRuntimeValues: UntypedObjectArrayChecker,
+                    returnBehavior: ReturnBehavior.ReturnBlankIfAnyArgIsBlank,
+                    targetFunction: IsEmpty_UO)
+            },
             {
                 BuiltinFunctionsCore.IsError,
                 NoErrorHandling(IsError)

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

@@ -67,6 +67,19 @@ namespace Microsoft.PowerFx.Functions
             var result = element[0];
 
             return new UntypedObjectValue(irContext, result);
+        }
+
+        public static FormulaValue IsEmpty_UO(IRContext irContext, UntypedObjectValue[] args)
+        {
+            var element = args[0].Impl;
+            var len = element.GetArrayLength();
+
+            if (len == 0)
+            {
+                return FormulaValue.New(true);
+            }
+
+            return FormulaValue.New(false);
         }
 
         public static FormulaValue Last_UO(IRContext irContext, UntypedObjectValue[] args)

src/tests/Microsoft.PowerFx.Core.Tests.Shared/ExpressionTestCases/IsEmpty.txt

@@ -114,6 +114,16 @@ true
    ),a > 10))
 true
 
+// Untyped object
+>> IsEmpty(ParseJSON("[{""a"":1}]"))
+false
+
+>> IsEmpty(ParseJSON("[]"))
+true
+
+>> IsEmpty(ParseJSON("1"))
+Error({Kind:ErrorKind.InvalidArgument})
+
 // INVALID ARGUMENTS
 >> IsEmpty("")
 Errors: Error 8-10: Invalid argument type (Text). Expecting a Table value instead.