Escape every delimiter when displaying quoted identifiers

src/ast/mod.rs

@@ -382,8 +382,16 @@ impl fmt::Display for Ident {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         match self.quote_style {
             Some(q) if q == '"' || q == '\'' || q == '`' => {
-                let escaped = value::escape_quoted_string(&self.value, q);
-                write!(f, "{q}{escaped}{q}")
+                // The value is the decoded identifier, so every delimiter
+                // inside it is literal and must be doubled.
+                write!(f, "{q}")?;
+                for (i, part) in self.value.split(q).enumerate() {
+                    if i > 0 {
+                        write!(f, "{q}{q}")?;
+                    }
+                    f.write_str(part)?;
+                }
+                write!(f, "{q}")
             }
             Some('[') => write!(f, "[{}]", self.value),
             None => f.write_str(&self.value),

tests/sqlparser_common.rs

@@ -20060,3 +20060,46 @@ fn parse_insert_by_name() {
         _ => unreachable!(),
     }
 }
+
+#[test]
+fn parse_quoted_identifier_with_consecutive_delimiters() {
+    let dialects = all_dialects_where(|d| d.is_delimited_identifier_start('"'));
+    let select = dialects.verified_only_select(r#"SELECT "a""""b""#);
+    assert_eq!(
+        &Expr::Identifier(Ident::with_quote('"', r#"a""b"#)),
+        expr_from_projection(&select.projection[0]),
+    );
+
+    let dialects = all_dialects_where(|d| d.is_delimited_identifier_start('`'));
+    let select = dialects.verified_only_select("SELECT `a````b`");
+    assert_eq!(
+        &Expr::Identifier(Ident::with_quote('`', "a``b")),
+        expr_from_projection(&select.projection[0]),
+    );
+}
+
+#[test]
+fn quoted_identifier_display_round_trips() {
+    // Every value of length 1..=4 over the delimiter, a backslash, an ASCII
+    // and a multi-byte character, serialized and parsed back.
+    for quote in ['"', '`'] {
+        let dialects = all_dialects_where(move |d| d.is_delimited_identifier_start(quote));
+        let mut values = vec![String::new()];
+        for _ in 0..4 {
+            values = values
+                .iter()
+                .flat_map(|v| [quote, '\\', 'a', 'é'].map(|c| format!("{v}{c}")))
+                .collect();
+            for value in &values {
+                let ident = Ident::with_quote(quote, value.as_str());
+                let sql = format!("SELECT {ident}");
+                let select = dialects.verified_only_select(&sql);
+                assert_eq!(
+                    &Expr::Identifier(ident),
+                    expr_from_projection(&select.projection[0]),
+                    "{sql} did not round trip",
+                );
+            }
+        }
+    }
+}

tests/sqlparser_mysql.rs

@@ -1514,7 +1514,9 @@ fn parse_escaped_quote_identifiers_with_no_escape() {
                 require_semicolon_stmt_delimiter: true,
             }
         )
-        .verified_stmt(sql),
+        .parse_sql_statements(sql)
+        .unwrap()
+        .remove(0),
         Statement::Query(Box::new(Query {
             with: None,
             body: Box::new(SetExpr::Select(Box::new(Select {
@@ -1616,7 +1618,9 @@ fn parse_escaped_backticks_with_no_escape() {
             vec![Box::new(MySqlDialect {})],
             ParserOptions::new().with_unescape(false)
         )
-        .verified_stmt(sql),
+        .parse_sql_statements(sql)
+        .unwrap()
+        .remove(0),
         Statement::Query(Box::new(Query {
             with: None,
             body: Box::new(SetExpr::Select(Box::new(Select {