sqlparser_custom_dialect.rs

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! Test the ability for dialects to override parsing

use sqlparser::{
    ast::{BinaryOperator, Expr, Statement, Value},
    dialect::Dialect,
    keywords::Keyword,
    parser::{Parser, ParserError},
    tokenizer::Token,
};

#[test]
fn custom_prefix_parser() -> Result<(), ParserError> {
    #[derive(Debug)]
    struct MyDialect {}

    impl Dialect for MyDialect {
        fn is_identifier_start(&self, ch: char) -> bool {
            is_identifier_start(ch)
        }

        fn is_identifier_part(&self, ch: char) -> bool {
            is_identifier_part(ch)
        }

        fn parse_prefix(&self, parser: &mut Parser) -> Option<Result<Expr, ParserError>> {
            if parser.consume_token(&Token::Number("1".to_string(), false)) {
                Some(Ok(Expr::Value(Value::Null)))
            } else {
                None
            }
        }
    }

    let dialect = MyDialect {};
    let sql = "SELECT 1 + 2";
    let ast = Parser::parse_sql(&dialect, sql)?;
    let query = &ast[0];
    assert_eq!("SELECT NULL + 2", &format!("{}", query));
    Ok(())
}

#[test]
fn custom_infix_parser() -> Result<(), ParserError> {
    #[derive(Debug)]
    struct MyDialect {}

    impl Dialect for MyDialect {
        fn is_identifier_start(&self, ch: char) -> bool {
            is_identifier_start(ch)
        }

        fn is_identifier_part(&self, ch: char) -> bool {
            is_identifier_part(ch)
        }

        fn parse_infix(
            &self,
            parser: &mut Parser,
            expr: &Expr,
            _precendence: u8,
        ) -> Option<Result<Expr, ParserError>> {
            if parser.consume_token(&Token::Plus) {
                Some(Ok(Expr::BinaryOp {
                    left: Box::new(expr.clone()),
                    op: BinaryOperator::Multiply, // translate Plus to Multiply
                    right: Box::new(parser.parse_expr().unwrap()),
                }))
            } else {
                None
            }
        }
    }

    let dialect = MyDialect {};
    let sql = "SELECT 1 + 2";
    let ast = Parser::parse_sql(&dialect, sql)?;
    let query = &ast[0];
    assert_eq!("SELECT 1 * 2", &format!("{}", query));
    Ok(())
}

#[test]
fn custom_statement_parser() -> Result<(), ParserError> {
    #[derive(Debug)]
    struct MyDialect {}

    impl Dialect for MyDialect {
        fn is_identifier_start(&self, ch: char) -> bool {
            is_identifier_start(ch)
        }

        fn is_identifier_part(&self, ch: char) -> bool {
            is_identifier_part(ch)
        }

        fn parse_statement(&self, parser: &mut Parser) -> Option<Result<Statement, ParserError>> {
            if parser.parse_keyword(Keyword::SELECT) {
                for _ in 0..3 {
                    let _ = parser.next_token();
                }
                Some(Ok(Statement::Commit { chain: false }))
            } else {
                None
            }
        }
    }

    let dialect = MyDialect {};
    let sql = "SELECT 1 + 2";
    let ast = Parser::parse_sql(&dialect, sql)?;
    let query = &ast[0];
    assert_eq!("COMMIT", &format!("{}", query));
    Ok(())
}

fn is_identifier_start(ch: char) -> bool {
    ('a'..='z').contains(&ch) || ('A'..='Z').contains(&ch) || ch == '_'
}

fn is_identifier_part(ch: char) -> bool {
    ('a'..='z').contains(&ch)
        || ('A'..='Z').contains(&ch)
        || ('0'..='9').contains(&ch)
        || ch == '$'
        || ch == '_'
}