recursive select calls are parsed with bad trailing_commas parameter

Author: tomershaniii

src/parser/mod.rs

@@ -3516,16 +3516,11 @@ impl<'a> Parser<'a> {
         // e.g. `SELECT 1, 2, FROM t`
         // https://cloud.google.com/bigquery/docs/reference/standard-sql/lexical#trailing_commas
         // https://docs.snowflake.com/en/release-notes/2024/8_11#select-supports-trailing-commas
-        //
-        // This pattern could be captured better with RAII type semantics, but it's quite a bit of
-        // code to add for just one case, so we'll just do it manually here.
-        let old_value = self.options.trailing_commas;
-        self.options.trailing_commas |= self.dialect.supports_projection_trailing_commas();
 
-        let ret = self.parse_comma_separated(|p| p.parse_select_item());
-        self.options.trailing_commas = old_value;
+        let trailing_commas =
+            self.options.trailing_commas | self.dialect.supports_projection_trailing_commas();
 
-        ret
+        self.parse_comma_separated_with_trailing_commas(|p| p.parse_select_item(), trailing_commas)
     }
 
     pub fn parse_actions_list(&mut self) -> Result<Vec<ParsedAction>, ParserError> {
@@ -3552,11 +3547,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse the comma of a comma-separated syntax element.
+    /// Allows for control over trailing commas
     /// Returns true if there is a next element
-    fn is_parse_comma_separated_end(&mut self) -> bool {
+    fn is_parse_comma_separated_end_with_trailing_commas(&mut self, trailing_commas: bool) -> bool {
         if !self.consume_token(&Token::Comma) {
             true
-        } else if self.options.trailing_commas {
+        } else if trailing_commas {
             let token = self.peek_token().token;
             match token {
                 Token::Word(ref kw)
@@ -3574,15 +3570,34 @@ impl<'a> Parser<'a> {
         }
     }
 
+    /// Parse the comma of a comma-separated syntax element.
+    /// Returns true if there is a next element
+    fn is_parse_comma_separated_end(&mut self) -> bool {
+        self.is_parse_comma_separated_end_with_trailing_commas(self.options.trailing_commas)
+    }
+
     /// Parse a comma-separated list of 1+ items accepted by `F`
-    pub fn parse_comma_separated<T, F>(&mut self, mut f: F) -> Result<Vec<T>, ParserError>
+    pub fn parse_comma_separated<T, F>(&mut self, f: F) -> Result<Vec<T>, ParserError>
+    where
+        F: FnMut(&mut Parser<'a>) -> Result<T, ParserError>,
+    {
+        self.parse_comma_separated_with_trailing_commas(f, self.options.trailing_commas)
+    }
+
+    /// Parse a comma-separated list of 1+ items accepted by `F`
+    /// Allows for control over trailing commas
+    fn parse_comma_separated_with_trailing_commas<T, F>(
+        &mut self,
+        mut f: F,
+        trailing_commas: bool,
+    ) -> Result<Vec<T>, ParserError>
     where
         F: FnMut(&mut Parser<'a>) -> Result<T, ParserError>,
     {
         let mut values = vec![];
         loop {
             values.push(f(self)?);
-            if self.is_parse_comma_separated_end() {
+            if self.is_parse_comma_separated_end_with_trailing_commas(trailing_commas) {
                 break;
             }
         }

tests/sqlparser_snowflake.rs

@@ -2846,3 +2846,17 @@ fn test_parse_show_columns_sql() {
     snowflake().verified_stmt("SHOW COLUMNS IN TABLE abc");
     snowflake().verified_stmt("SHOW COLUMNS LIKE '%xyz%' IN TABLE abc");
 }
+
+#[test]
+fn test_projection_with_nested_trailing_commas() {
+    let sql = "SELECT a FROM b, LATERAL FLATTEN(input => events)";
+    let _ = snowflake().parse_sql_statements(&sql).unwrap();
+
+    //Single nesting
+    let sql = format!("SELECT ({sql})");
+    let _ = snowflake().parse_sql_statements(&sql).unwrap();
+
+    //Double nesting
+    let sql = format!("SELECT ({sql})");
+    let _ = snowflake().parse_sql_statements(&sql).unwrap();
+}