Added support for Mysql Backslash escapes (enabled by default) (#844)

Author: cobyge

src/tokenizer.rs

@@ -1094,29 +1094,40 @@ impl<'a> Tokenizer<'a> {
 
         chars.next(); // consume the opening quote
 
-        // slash escaping is specific to MySQL dialect
-        let mut is_escaped = false;
         while let Some(&ch) = chars.peek() {
             match ch {
                 char if char == quote_style => {
                     chars.next(); // consume
-                    if is_escaped {
-                        s.push(ch);
-                        is_escaped = false;
-                    } else if chars.peek().map(|c| *c == quote_style).unwrap_or(false) {
+                    if chars.peek().map(|c| *c == quote_style).unwrap_or(false) {
                         s.push(ch);
                         chars.next();
                     } else {
                         return Ok(s);
                     }
                 }
                 '\\' => {
+                    // consume
+                    chars.next();
+                    // slash escaping is specific to MySQL dialect
                     if dialect_of!(self is MySqlDialect) {
-                        is_escaped = !is_escaped;
+                        if let Some(next) = chars.peek() {
+                            // See https://dev.mysql.com/doc/refman/8.0/en/string-literals.html#character-escape-sequences
+                            let n = match next {
+                                '\'' | '\"' | '\\' | '%' | '_' => *next,
+                                '0' => '\0',
+                                'b' => '\u{8}',
+                                'n' => '\n',
+                                'r' => '\r',
+                                't' => '\t',
+                                'Z' => '\u{1a}',
+                                _ => *next,
+                            };
+                            s.push(n);
+                            chars.next(); // consume next
+                        }
                     } else {
                         s.push(ch);
                     }
-                    chars.next();
                 }
                 _ => {
                     chars.next(); // consume

tests/sqlparser_mysql.rs

@@ -518,35 +518,34 @@ fn parse_unterminated_escape() {
 
 #[test]
 fn parse_escaped_string() {
-    let sql = r#"SELECT 'I\'m fine'"#;
-
-    let stmt = mysql().one_statement_parses_to(sql, "");
-
-    match stmt {
-        Statement::Query(query) => match *query.body {
-            SetExpr::Select(value) => {
-                let expr = expr_from_projection(only(&value.projection));
-                assert_eq!(
-                    *expr,
-                    Expr::Value(Value::SingleQuotedString("I'm fine".to_string()))
-                );
-            }
+    fn assert_mysql_query_value(sql: &str, quoted: &str) {
+        let stmt = mysql().one_statement_parses_to(sql, "");
+
+        match stmt {
+            Statement::Query(query) => match *query.body {
+                SetExpr::Select(value) => {
+                    let expr = expr_from_projection(only(&value.projection));
+                    assert_eq!(
+                        *expr,
+                        Expr::Value(Value::SingleQuotedString(quoted.to_string()))
+                    );
+                }
+                _ => unreachable!(),
+            },
             _ => unreachable!(),
-        },
-        _ => unreachable!(),
-    };
+        };
+    }
+    let sql = r#"SELECT 'I\'m fine'"#;
+    assert_mysql_query_value(sql, "I'm fine");
 
     let sql = r#"SELECT 'I''m fine'"#;
+    assert_mysql_query_value(sql, "I'm fine");
 
-    let projection = mysql().verified_only_select(sql).projection;
-    let item = projection.get(0).unwrap();
+    let sql = r#"SELECT 'I\"m fine'"#;
+    assert_mysql_query_value(sql, "I\"m fine");
 
-    match &item {
-        SelectItem::UnnamedExpr(Expr::Value(value)) => {
-            assert_eq!(*value, Value::SingleQuotedString("I'm fine".to_string()));
-        }
-        _ => unreachable!(),
-    }
+    let sql = r#"SELECT 'Testing: \0 \\ \% \_ \b \n \r \t \Z \a \ '"#;
+    assert_mysql_query_value(sql, "Testing: \0 \\ % _ \u{8} \n \r \t \u{1a} a  ");
 }
 
 #[test]