Reject IF NOT EXISTS for PostgreSQL CREATE ROLE

Author: LucaCappelletti94

src/dialect/mod.rs

@@ -410,6 +410,11 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns true if `CREATE ROLE` accepts `IF NOT EXISTS`.
+    fn supports_create_role_if_not_exists(&self) -> bool {
+        true
+    }
+
     /// Returns true if the dialects supports `group sets, roll up, or cube` expressions.
     fn supports_group_by_expr(&self) -> bool {
         false

src/dialect/postgresql.rs

@@ -198,6 +198,10 @@ impl Dialect for PostgreSqlDialect {
         true
     }
 
+    fn supports_create_role_if_not_exists(&self) -> bool {
+        false
+    }
+
     fn prec_value(&self, prec: Precedence) -> u8 {
         match prec {
             Precedence::Period => PERIOD_PREC,

src/parser/mod.rs

@@ -7037,15 +7037,17 @@ impl<'a> Parser<'a> {
         &mut self,
         role_keyword: RoleKeyword,
     ) -> Result<CreateRole, ParserError> {
-        if matches!(role_keyword, RoleKeyword::Group)
+        let supports_if_not_exists = matches!(role_keyword, RoleKeyword::Role)
+            && self.dialect.supports_create_role_if_not_exists();
+        if !supports_if_not_exists
             && self.peek_keywords(&[Keyword::IF, Keyword::NOT, Keyword::EXISTS])
         {
             return parser_err!(
-                "IF NOT EXISTS is not supported for CREATE GROUP",
+                format!("IF NOT EXISTS is not supported for CREATE {role_keyword}"),
                 self.peek_token_ref().span.start
             );
         }
-        let if_not_exists = matches!(role_keyword, RoleKeyword::Role)
+        let if_not_exists = supports_if_not_exists
             && self.parse_keywords(&[Keyword::IF, Keyword::NOT, Keyword::EXISTS]);
         let names = self.parse_comma_separated(|p| p.parse_object_name(false))?;
 

tests/sqlparser_common.rs

@@ -10081,7 +10081,7 @@ fn parse_create_role() {
     }
 
     let sql = "CREATE ROLE IF NOT EXISTS mysql_a, mysql_b";
-    match verified_stmt(sql) {
+    match all_dialects_where(|d| d.supports_create_role_if_not_exists()).verified_stmt(sql) {
         Statement::CreateRole(create_role) => {
             assert_eq_vec(&["mysql_a", "mysql_b"], &create_role.names);
             assert!(create_role.if_not_exists);

tests/sqlparser_postgres.rs

@@ -4453,11 +4453,11 @@ fn parse_operator_empty_parens_rejected() {
 
 #[test]
 fn parse_create_role() {
-    let sql = "CREATE ROLE IF NOT EXISTS mysql_a, mysql_b";
+    let sql = "CREATE ROLE mysql_a, mysql_b";
     match pg().verified_stmt(sql) {
         Statement::CreateRole(create_role) => {
             assert_eq_vec(&["mysql_a", "mysql_b"], &create_role.names);
-            assert!(create_role.if_not_exists);
+            assert!(!create_role.if_not_exists);
         }
         _ => unreachable!(),
     }
@@ -10295,3 +10295,14 @@ fn parse_user_group_statements_is_dialect_gated() {
         );
     }
 }
+
+#[test]
+fn parse_create_role_if_not_exists_rejected() {
+    assert_eq!(
+        pg().parse_sql_statements("CREATE ROLE IF NOT EXISTS r"),
+        Err(ParserError::ParserError(
+            "IF NOT EXISTS is not supported for CREATE ROLE".to_string()
+        ))
+    );
+    pg().verified_stmt(r#"CREATE ROLE "IF""#);
+}