Gregli/free self var

src/libraries/Microsoft.PowerFx.Core/Public/Config/Features.cs

@@ -77,6 +77,16 @@ public sealed class Features
         /// </summary>
         internal bool IsUserDefinedTypesEnabled { get; init; } = false;
 
+        /// <summary>
+        /// Enhanced checks for iteration functions (ForAll, Sum, AddColumns, ...) for:
+        /// 1. Recalc engine Set function is not allowed in the lambda of an iteration, in the same manner that 
+        ///    Clear and ClearCollect are not allowed. The Canvas Set function was already blocked. 
+        /// 2. Global variables are blocked from self-modification, just as data sources have always been.
+        ///    This became problematic when Canvas changed collection from being based on a data source to being based on a global variable.
+        /// This will break existing formulas and cannot be included in V1.
+        /// </summary>
+        internal bool EnhancedIterationChecks { get; init; }
+
         internal static readonly Features None = new Features();
 
         /// <summary>
@@ -100,6 +110,11 @@ public sealed class Features
             IsUserDefinedTypesEnabled = true
         };
 
+        public static readonly Features PowerFxV2 = new Features(_powerFxV1)
+        {
+            EnhancedIterationChecks = true
+        };
+
         internal Features()
         {
         }
@@ -118,6 +133,7 @@ internal Features(Features other)
             IsUserDefinedTypesEnabled = other.IsUserDefinedTypesEnabled;
             AsTypeLegacyCheck = other.AsTypeLegacyCheck;
             JsonFunctionAcceptsLazyTypes = other.JsonFunctionAcceptsLazyTypes;
+            EnhancedIterationChecks = other.EnhancedIterationChecks;
         }
     }
 }

src/libraries/Microsoft.PowerFx.Repl/Repl.cs

@@ -72,6 +72,8 @@ public class PowerFxREPL
 
         public ParserOptions ParserOptions { get; set; } = new ParserOptions() { AllowsSideEffects = true };
 
+        public SymbolProperties VariableSymbolProperties { get; set; } = new SymbolProperties { CanMutate = true, CanSet = true };
+
         // example override, switching to [1], [2] etc.
         public virtual string Prompt => "\n>> ";
 
@@ -444,7 +446,7 @@ await this.Output.WriteLineAsync($"Error: Can't set '{name}' to a Void value.",
                         // Start as blank. Will execute expression below to actually assign. 
                         var setValue = FormulaValue.NewBlank(setCheck.ReturnType);
 
-                        this.Engine.UpdateVariable(name, setValue);
+                        this.Engine.UpdateVariable(name, setValue, VariableSymbolProperties);
 
                         createdDeclarations = true;
                     }

src/tests/Microsoft.PowerFx.Core.Tests.Shared/Helpers/TestTabularDataSource.cs

@@ -45,11 +45,14 @@ internal class TestDelegationMetadata : IDelegationMetadata
 
         private readonly FilterOpMetadata _filterDelegationMetadata;
 
-        public TestDelegationMetadata(DelegationCapability capability = default, DType schema = default, Core.Functions.Delegation.DelegationMetadata.FilterOpMetadata filterDelegationMetadata = default)
+        private readonly SortOpMetadata _sortDelegationMetadata;
+
+        public TestDelegationMetadata(DelegationCapability capability = default, DType schema = default, FilterOpMetadata filterDelegationMetadata = default, SortOpMetadata sortDelegationMetadata = default)
         {
             _capability = capability;
             _schema = schema ?? EntityRecordType._type;
             _filterDelegationMetadata = filterDelegationMetadata;
+            _sortDelegationMetadata = sortDelegationMetadata;
         }
 
         public static RecordType EntityRecordType => RecordType.Empty()
@@ -62,7 +65,7 @@ public TestDelegationMetadata(DelegationCapability capability = default, DType s
 
         public DelegationCapability TableCapabilities => _capability;
 
-        public SortOpMetadata SortDelegationMetadata => throw new NotImplementedException();
+        public SortOpMetadata SortDelegationMetadata => _sortDelegationMetadata;
 
         public FilterOpMetadata FilterDelegationMetadata => _filterDelegationMetadata;
 
@@ -93,7 +96,7 @@ public bool TryGetEntity<T>(DName currentEntityEntityName, out T externalEntity)
             if (_symbol.TryGetVariable(currentEntityEntityName, out NameLookupInfo lookupInfo, out _))
             {
                 externalEntity = lookupInfo.Data as T;
-                return true;
+                return externalEntity != null;
             }
 
             return false;
@@ -197,7 +200,7 @@ internal TestDataSource(string name, DType schema, string[] keyColumns = null, I
 
         public virtual bool IsDelegatable => throw new NotImplementedException();
 
-        public bool RequiresAsync => throw new NotImplementedException();
+        public bool RequiresAsync => false;
 
         public IExternalDataEntityMetadataProvider DataEntityMetadataProvider => ExternalDataEntityMetadataProvider;
 
@@ -221,13 +224,13 @@ internal TestDataSource(string name, DType schema, string[] keyColumns = null, I
 
         public BidirectionalDictionary<string, string> PreviousDisplayNameMapping => null;
 
-        public bool IsRefreshable => throw new NotImplementedException();
+        public bool IsRefreshable => true;
 
         IDelegationMetadata IExternalDataSource.DelegationMetadata => DelegationMetadata;
 
         public bool IsWritable => true;
 
-        public bool IsClearable => throw new NotImplementedException();
+        public bool IsClearable => true;
 
         public bool CanIncludeExpand(IExpandInfo expandToAdd)
         {