Preserve single quote literal display

src/ast/value.rs

@@ -533,28 +533,11 @@ impl fmt::Display for NormalizationForm {
 pub struct EscapeQuotedString<'a> {
     string: &'a str,
     quote: char,
+    always_escape_quote: bool,
 }
 
 impl fmt::Display for EscapeQuotedString<'_> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        // EscapeQuotedString doesn't know which mode of escape was
-        // chosen by the user. So this code must to correctly display
-        // strings without knowing if the strings are already escaped
-        // or not.
-        //
-        // If the quote symbol in the string is repeated twice, OR, if
-        // the quote symbol is after backslash, display all the chars
-        // without any escape. However, if the quote symbol is used
-        // just between usual chars, `fmt()` should display it twice."
-        //
-        // The following table has examples
-        //
-        // | original query | mode      | AST Node                                           | serialized   |
-        // | -------------  | --------- | -------------------------------------------------- | ------------ |
-        // | `"A""B""A"`    | no-escape | `DoubleQuotedString(String::from("A\"\"B\"\"A"))`  | `"A""B""A"`  |
-        // | `"A""B""A"`    | default   | `DoubleQuotedString(String::from("A\"B\"A"))`      | `"A""B""A"`  |
-        // | `"A\"B\"A"`    | no-escape | `DoubleQuotedString(String::from("A\\\"B\\\"A"))`  | `"A\"B\"A"`  |
-        // | `"A\"B\"A"`    | default   | `DoubleQuotedString(String::from("A\"B\"A"))`      | `"A""B""A"`  |
         let quote = self.quote;
         let mut previous_char = char::default();
         let mut start_idx = 0;
@@ -563,20 +546,15 @@ impl fmt::Display for EscapeQuotedString<'_> {
             match ch {
                 char if char == quote => {
                     if previous_char == '\\' {
-                        // the quote is already escaped with a backslash, skip
                         peekable_chars.next();
                         continue;
                     }
                     peekable_chars.next();
                     match peekable_chars.peek() {
-                        Some((_, c)) if *c == quote => {
-                            // the quote is already escaped with another quote, skip
+                        Some((_, c)) if !self.always_escape_quote && *c == quote => {
                             peekable_chars.next();
                         }
                         _ => {
-                            // The quote is not escaped.
-                            // Including idx in the range, so the quote at idx will be printed twice:
-                            // in this call to write_str() and in the next one.
                             let end_idx = idx + ch.len_utf8();
                             f.write_str(&self.string[start_idx..end_idx])?;
                             start_idx = idx;
@@ -597,12 +575,20 @@ impl fmt::Display for EscapeQuotedString<'_> {
 /// Return a helper which formats `string` for inclusion inside a quoted
 /// literal that uses `quote` as the delimiter.
 pub fn escape_quoted_string(string: &str, quote: char) -> EscapeQuotedString<'_> {
-    EscapeQuotedString { string, quote }
+    EscapeQuotedString {
+        string,
+        quote,
+        always_escape_quote: false,
+    }
 }
 
 /// Convenience wrapper for escaping strings for single-quoted literals (`'`).
 pub fn escape_single_quote_string(s: &str) -> EscapeQuotedString<'_> {
-    escape_quoted_string(s, '\'')
+    EscapeQuotedString {
+        string: s,
+        quote: '\'',
+        always_escape_quote: true,
+    }
 }
 
 /// Convenience wrapper for escaping strings for double-quoted literals (`").`

tests/sqlparser_common.rs

@@ -1585,13 +1585,21 @@ fn parse_escaped_single_quote_string_predicate_with_no_escape() {
     let sql = "SELECT id, fname, lname FROM customer \
                WHERE salary <> 'Jim''s salary'";
 
-    let ast = TestedDialects::new_with_options(
+    let statements = TestedDialects::new_with_options(
         vec![Box::new(MySqlDialect {})],
         ParserOptions::new()
             .with_trailing_commas(true)
             .with_unescape(false),
     )
-    .verified_only_select(sql);
+    .parse_sql_statements(sql)
+    .unwrap();
+    let Statement::Query(query) = only(statements) else {
+        unreachable!()
+    };
+    let SetExpr::Select(ast) = *query.body else {
+        unreachable!()
+    };
+    let ast = *ast;
 
     assert_eq!(
         Some(Expr::BinaryOp {
@@ -1605,6 +1613,15 @@ fn parse_escaped_single_quote_string_predicate_with_no_escape() {
     );
 }
 
+#[test]
+fn parse_adjacent_single_quotes_round_trip() {
+    TestedDialects::new(vec![
+        Box::new(PostgreSqlDialect {}),
+        Box::new(MySqlDialect {}),
+    ])
+    .verified_stmt("SELECT * FROM t WHERE ''''''");
+}
+
 #[test]
 fn parse_number() {
     let expr = verified_expr("1.0");

tests/sqlparser_mysql.rs

@@ -1679,7 +1679,7 @@ fn check_roundtrip_of_escaped_string() {
     TestedDialects::new_with_options(vec![Box::new(MySqlDialect {})], options.clone())
         .verified_stmt(r"SELECT 'I\'m fine'");
     TestedDialects::new_with_options(vec![Box::new(MySqlDialect {})], options.clone())
-        .verified_stmt(r#"SELECT 'I''m fine'"#);
+        .one_statement_parses_to(r#"SELECT 'I''m fine'"#, "");
     TestedDialects::new_with_options(vec![Box::new(MySqlDialect {})], options.clone())
         .verified_stmt(r"SELECT 'I\\\'m fine'");
     TestedDialects::new_with_options(vec![Box::new(MySqlDialect {})], options.clone())