Fix OptionSets in symbol tables (#2705)

Make sure composed tables return all option sets

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

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection.Metadata;
 using Microsoft.PowerFx.Core.Binding;
 using Microsoft.PowerFx.Core.Binding.BindInfo;
 using Microsoft.PowerFx.Core.Entities;
@@ -163,6 +164,20 @@ namespace Microsoft.PowerFx
             }
         }
 
+        public override IEnumerable<KeyValuePair<string, OptionSet>> OptionSets
+        {
+            get
+            {
+                foreach (ReadOnlySymbolTable st in _symbolTables)
+                {
+                    foreach (KeyValuePair<string, OptionSet> kvp in st.OptionSets)
+                    {
+                        yield return kvp;
+                    }
+                }
+            }
+        }
+
         public virtual bool Lookup(DName name, out NameLookupInfo nameInfo, NameLookupPreferences preferences = NameLookupPreferences.None)
         {
             foreach (INameResolver table in _symbolTables)

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

@@ -347,8 +347,8 @@ namespace Microsoft.PowerFx
 
         public IEnumerable<string> FunctionNames => this.Functions.FunctionNames;
 
-        public IEnumerable<KeyValuePair<string, OptionSet>> OptionSets => _variables.Where(kvp => kvp.Value.Kind == BindKind.OptionSet)
-                                                                                    .Select(kvp => new KeyValuePair<string, OptionSet>(kvp.Key, (OptionSet)kvp.Value.Data));
+        public virtual IEnumerable<KeyValuePair<string, OptionSet>> OptionSets => _variables.Where(kvp => kvp.Value.Kind == BindKind.OptionSet)
+                                                                                            .Select(kvp => new KeyValuePair<string, OptionSet>(kvp.Key, (OptionSet)kvp.Value.Data));
 
         // Which enums are available. 
         // These do not compose - only bottom one wins. 

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

@@ -306,6 +306,25 @@ namespace Microsoft.PowerFx.Core.Tests
             Assert.Equal(2, func3.Count());
         }
 
+        [Fact]
+        public void OptionSetTests()
+        {
+            var os1 = new OptionSet("os1", DisplayNameProvider.New(new Dictionary<DName, DName>() { { new DName("ln1"), new DName("dn1") } }));
+            var os2 = new OptionSet("os2", DisplayNameProvider.New(new Dictionary<DName, DName>() { { new DName("ln2"), new DName("dn2") }, { new DName("ln3"), new DName("dn3") } }));
+            
+            var st1 = new SymbolTable();
+            st1.AddOptionSet(os1);
+
+            Assert.Single(st1.OptionSets);
+
+            var st2 = new SymbolTable();
+            st2.AddOptionSet(os2);
+
+            var st3 = SymbolTable.Compose(st1, st2);
+
+            Assert.Equal(2, st3.OptionSets.Count());            
+        }
+
         [Fact]
         public void VoidIsNotAllowed()
         {