Debug: Add diagnostic logging to JSON type mappings

Added Console.WriteLine statements to track:
- When MySqlComplexJsonTypeMapping is created/cloned
- When GetDataReaderMethod() is called
- When CustomizeDataReaderExpression() is called and what conversions happen
- When MySqlTypeMappingSource returns complex vs regular JSON mappings

This will help diagnose the SQL syntax errors in bulk update scenarios.

Co-authored-by: renemadsen <76994+renemadsen@users.noreply.github.com>

Author: Copilot

src/EFCore.MySql/Storage/Internal/MySqlJsonTypeMapping.cs

@@ -33,6 +33,7 @@ public MySqlComplexJsonTypeMapping(
             bool replaceLineBreaksWithCharFunction)
             : base(storeType, valueConverter, valueComparer, noBackslashEscapes, replaceLineBreaksWithCharFunction)
         {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping constructor called - StoreType: {storeType}, Converter: {valueConverter?.GetType().Name ?? "null"}");
         }
 
         protected MySqlComplexJsonTypeMapping(
@@ -42,30 +43,42 @@ protected MySqlComplexJsonTypeMapping(
             bool replaceLineBreaksWithCharFunction)
             : base(parameters, mySqlDbType, noBackslashEscapes, replaceLineBreaksWithCharFunction)
         {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping protected constructor called - ClrType: {ClrType?.Name ?? "null"}, StoreType: {StoreType}");
         }
 
         protected override RelationalTypeMapping Clone(RelationalTypeMappingParameters parameters)
-            => new MySqlComplexJsonTypeMapping(parameters, MySqlDbType, NoBackslashEscapes, ReplaceLineBreaksWithCharFunction);
+        {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping.Clone(parameters) called - ClrType: {parameters.CoreParameters.ClrType?.Name ?? "null"}");
+            return new MySqlComplexJsonTypeMapping(parameters, MySqlDbType, NoBackslashEscapes, ReplaceLineBreaksWithCharFunction);
+        }
 
         protected override RelationalTypeMapping Clone(bool? noBackslashEscapes = null, bool? replaceLineBreaksWithCharFunction = null)
-            => new MySqlComplexJsonTypeMapping(
+        {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping.Clone(bool) called - ClrType: {ClrType?.Name ?? "null"}, StoreType: {StoreType}");
+            return new MySqlComplexJsonTypeMapping(
                 Parameters,
                 MySqlDbType,
                 noBackslashEscapes ?? NoBackslashEscapes,
                 replaceLineBreaksWithCharFunction ?? ReplaceLineBreaksWithCharFunction);
+        }
 
         /// <summary>
         /// Returns the method to be used for reading JSON values from the database.
         /// MySQL stores JSON as strings, so we use GetString.
         /// </summary>
         public override MethodInfo GetDataReaderMethod()
-            => _getString;
+        {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping.GetDataReaderMethod() called - ClrType: {ClrType?.Name ?? "null"}, returning: {_getString?.Name ?? "null"}");
+            return _getString;
+        }
 
         /// <summary>
         /// For complex JSON, we ALWAYS convert string to MemoryStream.
         /// </summary>
         public override Expression CustomizeDataReaderExpression(Expression expression)
         {
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping.CustomizeDataReaderExpression() called - ExpressionType: {expression.Type?.Name ?? "null"}, ClrType: {ClrType?.Name ?? "null"}");
+            
             if (expression.Type == typeof(string))
             {
                 // Validate that reflection lookups succeeded (using cached members from base class)
@@ -75,6 +88,8 @@ public override Expression CustomizeDataReaderExpression(Expression expression)
                         "Failed to find required reflection members for JSON type mapping.");
                 }
 
+                Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping: Converting string expression to MemoryStream");
+                
                 // Convert string to MemoryStream: new MemoryStream(Encoding.UTF8.GetBytes(stringValue))
                 return Expression.New(
                     _memoryStreamCtor,
@@ -84,6 +99,7 @@ public override Expression CustomizeDataReaderExpression(Expression expression)
                         expression));
             }
 
+            Console.WriteLine($"[DEBUG] MySqlComplexJsonTypeMapping: No conversion, calling base.CustomizeDataReaderExpression");
             return base.CustomizeDataReaderExpression(expression);
         }
     }

src/EFCore.MySql/Storage/Internal/MySqlTypeMappingSource.cs

@@ -326,6 +326,7 @@ private RelationalTypeMapping FindRawMapping(RelationalTypeMappingInfo mappingIn
                     // when creating JSON columns for complex types/collections. Return our complex JSON mapping.
                     if (clrType?.Name == "JsonTypePlaceholder" && storeTypeName.Equals("json", StringComparison.OrdinalIgnoreCase))
                     {
+                        Console.WriteLine($"[DEBUG] MySqlTypeMappingSource: Detected JsonTypePlaceholder, returning _jsonComplexType");
                         return _jsonComplexType;
                     }
 
@@ -349,6 +350,7 @@ private RelationalTypeMapping FindRawMapping(RelationalTypeMappingInfo mappingIn
                 // Works for both MySQL (native JSON type) and MariaDB (JSON alias for LONGTEXT)
                 if (storeTypeName.Equals("json", StringComparison.OrdinalIgnoreCase))
                 {
+                    Console.WriteLine($"[DEBUG] MySqlTypeMappingSource: JSON store type with CLR type: {clrType?.Name ?? "null"}, returning _jsonDefaultString");
                     // Return JSON mapping for any CLR type since JSON can serialize any object
                     // The "json" store type works for both:
                     // - MySQL 5.7.8+: Creates native JSON column with binary storage