Fix scalar casting from string for POCO/DOM JSON mode (npgsql#3340)

Fixes npgsql#2774
Fixes npgsql#3158

Author: roji

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlJsonDomTranslator.cs

@@ -130,9 +130,11 @@ public NpgsqlJsonDomTranslator(
                 typeof(string),
                 _stringTypeMapping);
 
+            // The PostgreSQL traversal operator always returns text - for these scalar-returning methods, apply a conversion from string.
             return method.Name == nameof(JsonElement.GetString)
                 ? traversalToText
-                : ConvertFromText(traversalToText, method.ReturnType);
+                : _sqlExpressionFactory.Convert(
+                    traversalToText, method.ReturnType, _typeMappingSource.FindMapping(method.ReturnType, _model));
         }
 
         if (method == GetArrayLength)
@@ -152,30 +154,4 @@ public NpgsqlJsonDomTranslator(
 
         return null;
     }
-
-    // The PostgreSQL traversal operator always returns text, so we need to convert to int, bool, etc.
-    private SqlExpression ConvertFromText(SqlExpression expression, Type returnType)
-    {
-        switch (Type.GetTypeCode(returnType))
-        {
-            case TypeCode.Boolean:
-            case TypeCode.Byte:
-            case TypeCode.DateTime:
-            case TypeCode.Decimal:
-            case TypeCode.Double:
-            case TypeCode.Int16:
-            case TypeCode.Int32:
-            case TypeCode.Int64:
-            case TypeCode.SByte:
-            case TypeCode.Single:
-            case TypeCode.UInt16:
-            case TypeCode.UInt32:
-            case TypeCode.UInt64:
-                return _sqlExpressionFactory.Convert(expression, returnType, _typeMappingSource.FindMapping(returnType, _model));
-            default:
-                return returnType == typeof(Guid)
-                    ? _sqlExpressionFactory.Convert(expression, returnType, _typeMappingSource.FindMapping(returnType, _model))
-                    : expression;
-        }
-    }
 }

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlJsonPocoTranslator.cs

@@ -97,7 +97,8 @@ public NpgsqlJsonPocoTranslator(
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public virtual SqlExpression? TranslateMemberAccess(SqlExpression instance, SqlExpression member, Type returnType)
-        => instance switch
+    {
+        return instance switch
         {
             // The first time we see a JSON traversal it's on a column - create a JsonTraversalExpression.
             // Traversals on top of that get appended into the same expression.
@@ -119,6 +120,25 @@ PgJsonTraversalExpression prevPathTraversal
             _ => null
         };
 
+        // The PostgreSQL traversal operator always returns text.
+        // If the type returned is a scalar (int, bool, etc.), we need to apply a conversion from string.
+        SqlExpression ConvertFromText(SqlExpression expression, Type returnType)
+            => _typeMappingSource.FindMapping(returnType.UnwrapNullableType(), _model) switch
+            {
+                // Type mapping not found - this isn't a scalar
+                null => expression,
+
+                // Arrays are dealt with as JSON arrays, not array scalars
+                NpgsqlArrayTypeMapping => expression,
+
+                // Text types don't a a conversion to string
+                { StoreTypeNameBase: "text" or "varchar" or "char" } => expression,
+
+                // For any other type mapping, this is a scalar; apply a conversion to the type from string.
+                var mapping => _sqlExpressionFactory.Convert(expression, returnType, mapping)
+            };
+    }
+
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
     ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
@@ -159,38 +179,4 @@ PgJsonTraversalExpression prevPathTraversal
                 return null;
         }
     }
-
-    // The PostgreSQL traversal operator always returns text, so we need to convert to int, bool, etc.
-    private SqlExpression ConvertFromText(SqlExpression expression, Type returnType)
-    {
-        var unwrappedReturnType = returnType.UnwrapNullableType();
-
-        switch (Type.GetTypeCode(unwrappedReturnType))
-        {
-            case TypeCode.Boolean:
-            case TypeCode.Byte:
-            case TypeCode.DateTime:
-            case TypeCode.Decimal:
-            case TypeCode.Double:
-            case TypeCode.Int16:
-            case TypeCode.Int32:
-            case TypeCode.Int64:
-            case TypeCode.SByte:
-            case TypeCode.Single:
-            case TypeCode.UInt16:
-            case TypeCode.UInt32:
-            case TypeCode.UInt64:
-                return _sqlExpressionFactory.Convert(expression, returnType, _typeMappingSource.FindMapping(returnType, _model));
-        }
-
-        if (unwrappedReturnType == typeof(Guid)
-            || unwrappedReturnType == typeof(DateTimeOffset)
-            || unwrappedReturnType == typeof(DateOnly)
-            || unwrappedReturnType == typeof(TimeOnly))
-        {
-            return _sqlExpressionFactory.Convert(expression, returnType, _typeMappingSource.FindMapping(returnType, _model));
-        }
-
-        return expression;
-    }
 }