Escape closing brackets in bracket-quoted identifiers

src/ast/mod.rs

@@ -385,7 +385,19 @@ impl fmt::Display for Ident {
                 let escaped = value::escape_quoted_string(&self.value, q);
                 write!(f, "{q}{escaped}{q}")
             }
-            Some('[') => write!(f, "[{}]", self.value),
+            Some('[') => {
+                // Redshift nested quoted identifiers (e.g. `["a]b"]`) store the
+                // value as a complete double-quoted string whose inner `]` is
+                // literal, so leave those unchanged. Otherwise double each `]`,
+                // mirroring the tokenizer folding `]]` into `]`, so the
+                // identifier round-trips (#2409).
+                let v = &self.value;
+                if v.len() >= 2 && v.starts_with('"') && v.ends_with('"') {
+                    write!(f, "[{v}]")
+                } else {
+                    write!(f, "[{}]", v.replace(']', "]]"))
+                }
+            }
             None => f.write_str(&self.value),
             _ => panic!("unexpected quote style"),
         }

tests/sqlparser_mssql.rs

@@ -937,6 +937,18 @@ fn parse_table_name_in_square_brackets() {
     );
 }
 
+#[test]
+fn parse_bracket_identifier_with_escaped_closing_bracket() {
+    // A bracket-quoted identifier whose value contains `]` must serialize
+    // with the bracket doubled so it round-trips. See #2409.
+    let select = ms().verified_only_select("SELECT [a]]b]");
+    assert_eq!(
+        &Expr::Identifier(Ident::with_quote('[', "a]b")),
+        expr_from_projection(&select.projection[0]),
+    );
+    ms().verified_stmt("SELECT [a]]b] FROM [c]]d]");
+}
+
 #[test]
 fn parse_for_clause() {
     ms_and_generic().verified_stmt("SELECT a FROM t FOR JSON PATH");