Bug fix: NRE when writing non-existent keyed value to LTable.

Author: CXuesong

Luaon.NET/Linq/LTableStore.cs

@@ -115,8 +115,13 @@ public LField FieldFromName(LValue name, bool allowsCreation)
             Debug.Assert(name != null && name.TokenType != LTokenType.Nil);
             if (name.TokenType == LTokenType.Integer) return FieldFromName((int)name, name, allowsCreation);
             // Named field
-            if (fieldsDict.TryGetValue(name, out var field)) return field;
-            return null;
+            if (!fieldsDict.TryGetValue(name, out var field))
+            {
+                if (!allowsCreation) return null;
+                field = new LField(name, LValue.Nil);
+                Add(field);
+            }
+            return field;
         }
 
         public bool RemoveByName(LValue name)

XUnitTestProject1/Tests/RegressionTests.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using Luaon;
+using Luaon.Linq;
+using Xunit;
+
+namespace XUnitTestProject1.Tests
+{
+    public class RegressionTests
+    {
+
+        /// <summary>
+        /// UnexpectedCharacterException when parsing long Lua table (> LuaTableTextReader buffer size, i.e., 1024).
+        /// </summary>
+        [Fact]
+        public void Issue1()
+        {
+            var longString1 = string.Join("", Enumerable.Repeat("0123456789ABCDEF", 64)); // 16 x 64 = 1024
+            var longString2 = longString1 + "||" + longString1;
+            var bigTable = new LTable
+            {
+                ["Field1"] = longString1,
+                ["Field2"] = 12345,
+                ["Field2"] = longString2,
+            };
+            var serialized = bigTable.ToString(Formatting.Prettified);
+            Assert.Contains(longString1, serialized);
+            Assert.Contains(longString2, serialized);
+            var bigTable2 = LToken.Parse(serialized);
+            Assert.Equal(bigTable, bigTable2);
+        }
+
+    }
+}