🦺 enhance handling of MySQL string literals and default values (#115)

Author: techouse

src/mysql_to_sqlite3/transporter.py

@@ -324,6 +324,20 @@ def _transpile_mysql_expr_to_sqlite(cls, expr_sql: str) -> t.Optional[str]:
             )
             return None
 
+    @classmethod
+    def _normalize_literal_with_sqlglot(cls, expr_sql: str) -> t.Optional[str]:
+        """Normalize a MySQL literal using sqlglot, returning SQLite SQL if literal-like."""
+        cleaned: str = expr_sql.strip().rstrip(";")
+        try:
+            node: Expression = parse_one(cleaned, read="mysql")
+        except (ParseError, ValueError):
+            return None
+        if isinstance(node, exp.Literal):
+            return node.sql(dialect="sqlite")
+        if isinstance(node, exp.Paren) and isinstance(node.this, exp.Literal):
+            return node.this.sql(dialect="sqlite")
+        return None
+
     @staticmethod
     def _quote_sqlite_identifier(name: t.Union[str, bytes, bytearray]) -> str:
         """Safely quote an identifier for SQLite using sqlglot.
@@ -569,7 +583,15 @@ def _translate_default_from_mysql_to_sqlite(
                     # Allow simple arithmetic constant expressions composed of numbers and + - * /
                     if re.match(r"^[\d\.\s\+\-\*/\(\)]+$", norm) and any(ch.isdigit() for ch in norm):
                         return f"DEFAULT {norm}"
-            # Robustly escape single quotes for plain string defaults
+            stripped_default = column_default.strip()
+            if stripped_default.startswith("'") or (
+                stripped_default.startswith("(") and stripped_default.endswith(")")
+            ):
+                normalized_literal: t.Optional[str] = cls._normalize_literal_with_sqlglot(column_default)
+                if normalized_literal is not None:
+                    return f"DEFAULT {normalized_literal}"
+
+            # Fallback: robustly escape single quotes for plain string defaults
             _escaped = column_default.replace("\\'", "'")
             _escaped = _escaped.replace("'", "''")
             return f"DEFAULT '{_escaped}'"

tests/unit/test_types_and_defaults_extra.py

@@ -84,3 +84,12 @@ def test_translate_default_bool_boolean_type(self, monkeypatch: pytest.MonkeyPat
         monkeypatch.setattr(sqlite3, "sqlite_version", "3.40.0")
         assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite(True, column_type="BOOLEAN") == "DEFAULT(TRUE)"
         assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite(False, column_type="BOOLEAN") == "DEFAULT(FALSE)"
+
+    def test_translate_default_prequoted_string_literal(self) -> None:
+        # MariaDB can report TEXT defaults already wrapped in single quotes; ensure they're normalized
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("'[]'") == "DEFAULT '[]'"
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("'It''s'") == "DEFAULT 'It''s'"
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("'a\\'b'") == "DEFAULT 'a''b'"
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("''") == "DEFAULT ''"
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("('value')") == "DEFAULT 'value'"
+        assert MySQLtoSQLite._translate_default_from_mysql_to_sqlite("'tab\\there'") == "DEFAULT 'tab\there'"