[SIG-43614] Fix SQL parsing for select statement as function argument (#12)

* fix parsing on select statements as function arguments

* add tests

* remove whitespace

* fix next token no skip

* format fix

* restore next_token_no_skip and add fix me

Author: sinanunan

src/parser.rs

@@ -1220,6 +1220,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Return the first unprocessed token, possibly whitespace.
+    /// FIXME: This function skips the token
     pub fn next_token_no_skip(&mut self) -> Option<&Token> {
         self.index += 1;
         self.tokens.get(self.index - 1)
@@ -2783,6 +2784,13 @@ impl<'a> Parser<'a> {
 
             Ok(FunctionArg::Named { name, arg })
         } else {
+            // subqueries can be used in snowflake function calls without parantheses 
+            if dialect_of!(self is SnowflakeDialect) && 
+            (self.parse_keyword(Keyword::SELECT) || self.parse_keyword(Keyword::WITH))  {
+                self.prev_token();
+                let expr = Expr::Subquery(Box::new(self.parse_query()?));
+                return Ok(FunctionArg::Unnamed(expr))
+            }
             Ok(FunctionArg::Unnamed(self.parse_expr()?))
         }
     }

tests/sqlparser_snowflake.rs

@@ -151,6 +151,44 @@ fn test_single_table_in_parenthesis_with_alias() {
     );
 }
 
+
+#[test]
+fn parse_select_as_func_argument() {
+    // subquery without parantheses in function call should work
+    snowflake().one_statement_parses_to(
+        "SELECT parse_json(SELECT column2 FROM values(1, 'null'))",
+        "SELECT parse_json((SELECT column2 FROM values(1, 'null')))",
+    );
+    // subquery with parantheses in function call should also work
+    snowflake().one_statement_parses_to(
+        "SELECT parse_json((SELECT column2 FROM values(1, 'null')))",
+        "SELECT parse_json((SELECT column2 FROM values(1, 'null')))",
+    );
+     // subquery with comma in function call should be interpreted as function with one argument
+     // Ex: func(select 1, 2) === fun((select 1, 2))
+    snowflake().one_statement_parses_to(
+        "SELECT func(SELECT 1, 2)",
+        "SELECT func((SELECT 1, 2))",
+    );
+
+    // subquery starting with WITH should also work
+    snowflake().one_statement_parses_to(
+        "SELECT func(WITH foo AS (SELECT 1) SELECT 1)",
+        "SELECT func((WITH foo AS (SELECT 1) SELECT 1))",
+    );
+
+    // named function arguments should not work
+    let res = snowflake().parse_sql_statements(
+        "SELECT func(expr => SELECT 1)",
+    );
+    assert_eq!(
+        res.unwrap_err(),
+        ParserError::ParserError(
+            "SELECT func(expr => SELECT".to_string(),
+            "Expected ), found: 1".to_string()
+    ));
+}
+
 fn snowflake() -> TestedDialects {
     TestedDialects {
         dialects: vec![Box::new(SnowflakeDialect {})],