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LibSQL: Parse EXISTS expressions

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The EXISTS expression is a bit of an odd-man-out because it can appear
as any of the following forms:

    EXISTS (select-stmt)
    NOT EXISTS (select-stmt)
    (select-stmt)

Which makes it the only keyword expression that doesn't require its
keyword to actually be used. The consequence is that we might come
across an EXISTS expression while parsing another expression type;
NOT would have triggered a unary operator expression, and an opening
parentheses would have triggered an expression chain.
This commit is contained in:
Timothy Flynn 2021-04-23 15:29:28 -04:00 • committed by Andreas Kling
parent e62e76ca1a
commit 99b38aa3fa
4 changed files with 80 additions and 5 deletions
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35
Userland/Libraries/LibSQL/Parser.cpp
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@ -215,7 +215,6 @@ NonnullRefPtr<Expression> Parser::parse_expression()
// FIXME: Parse 'bind-parameter'.
// FIXME: Parse 'function-name'.
// FIXME: Parse 'exists'.
// FIXME: Parse 'raise-function'.
return expression;
@ -241,6 +240,9 @@ NonnullRefPtr<Expression> Parser::parse_primary_expression()
if (auto expression = parse_case_expression(); expression.has_value())
return move(expression.value());
if (auto expression = parse_exists_expression(false); expression.has_value())
return move(expression.value());
expected("Primary Expression");
consume();
@ -381,8 +383,12 @@ Optional<NonnullRefPtr<Expression>> Parser::parse_unary_operator_expression()
if (consume_if(TokenType::Tilde))
return create_ast_node<UnaryOperatorExpression>(UnaryOperator::BitwiseNot, parse_expression());
if (consume_if(TokenType::Not))
return create_ast_node<UnaryOperatorExpression>(UnaryOperator::Not, parse_expression());
if (consume_if(TokenType::Not)) {
if (match(TokenType::Exists))
return parse_exists_expression(true);
else
return create_ast_node<UnaryOperatorExpression>(UnaryOperator::Not, parse_expression());
}
return {};
}
@ -448,11 +454,15 @@ Optional<NonnullRefPtr<Expression>> Parser::parse_binary_operator_expression(Non
Optional<NonnullRefPtr<Expression>> Parser::parse_chained_expression()
{
if (!match(TokenType::ParenOpen))
if (!consume_if(TokenType::ParenOpen))
return {};
if (match(TokenType::Select))
return parse_exists_expression(false, TokenType::Select);
NonnullRefPtrVector<Expression> expressions;
parse_comma_separated_list(true, [&]() { expressions.append(parse_expression()); });
parse_comma_separated_list(false, [&]() { expressions.append(parse_expression()); });
consume(TokenType::ParenClose);
return create_ast_node<ChainedExpression>(move(expressions));
}
@ -506,6 +516,21 @@ Optional<NonnullRefPtr<Expression>> Parser::parse_case_expression()
return create_ast_node<CaseExpression>(move(case_expression), move(when_then_clauses), move(else_expression));
}
Optional<NonnullRefPtr<Expression>> Parser::parse_exists_expression(bool invert_expression, TokenType opening_token)
{
VERIFY((opening_token == TokenType::Exists) || (opening_token == TokenType::Select));
if ((opening_token == TokenType::Exists) && !consume_if(TokenType::Exists))
return {};
if (opening_token == TokenType::Exists)
consume(TokenType::ParenOpen);
auto select_statement = parse_select_statement({});
consume(TokenType::ParenClose);
return create_ast_node<ExistsExpression>(move(select_statement), invert_expression);
}
Optional<NonnullRefPtr<Expression>> Parser::parse_collate_expression(NonnullRefPtr<Expression> expression)
{
if (!match(TokenType::Collate))