rust/crates/ide-assists/src/handlers/remove_parentheses.rs

use syntax::{ast, AstNode};

use crate::{AssistContext, AssistId, AssistKind, Assists};

// Assist: remove_parentheses
//
// Removes redundant parentheses.
//
// ```
// fn main() {
//     _ = $0(2) + 2;
// }
// ```
// ->
// ```
// fn main() {
//     _ = 2 + 2;
// }
// ```
pub(crate) fn remove_parentheses(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
    let parens = ctx.find_node_at_offset::<ast::ParenExpr>()?;

    let cursor_in_range =
        parens.l_paren_token()?.text_range().contains_range(ctx.selection_trimmed())
            || parens.r_paren_token()?.text_range().contains_range(ctx.selection_trimmed());
    if !cursor_in_range {
        return None;
    }

    let expr = parens.expr()?;

    let parent = ast::Expr::cast(parens.syntax().parent()?);
    let is_ok_to_remove = expr.precedence() >= parent.as_ref().and_then(ast::Expr::precedence);
    if !is_ok_to_remove {
        return None;
    }

    let target = parens.syntax().text_range();
    acc.add(
        AssistId("remove_parentheses", AssistKind::Refactor),
        "Remove redundant parentheses",
        target,
        |builder| builder.replace_ast(parens.into(), expr),
    )
}

#[cfg(test)]
mod tests {
    use crate::tests::{check_assist, check_assist_not_applicable};

    use super::*;

    #[test]
    fn remove_parens_simple() {
        check_assist(remove_parentheses, r#"fn f() { $0(2) + 2; }"#, r#"fn f() { 2 + 2; }"#);
        check_assist(remove_parentheses, r#"fn f() { ($02) + 2; }"#, r#"fn f() { 2 + 2; }"#);
        check_assist(remove_parentheses, r#"fn f() { (2)$0 + 2; }"#, r#"fn f() { 2 + 2; }"#);
        check_assist(remove_parentheses, r#"fn f() { (2$0) + 2; }"#, r#"fn f() { 2 + 2; }"#);
    }

    #[test]
    fn remove_parens_precedence() {
        check_assist(
            remove_parentheses,
            r#"fn f() { $0(2 * 3) + 1; }"#,
            r#"fn f() { 2 * 3 + 1; }"#,
        );
        check_assist(remove_parentheses, r#"fn f() { ( $0(2) ); }"#, r#"fn f() { ( 2 ); }"#);
        check_assist(remove_parentheses, r#"fn f() { $0(2?)?; }"#, r#"fn f() { 2??; }"#);
        check_assist(remove_parentheses, r#"fn f() { f(($02 + 2)); }"#, r#"fn f() { f(2 + 2); }"#);
        check_assist(
            remove_parentheses,
            r#"fn f() { (1<2)&&$0(3>4); }"#,
            r#"fn f() { (1<2)&&3>4; }"#,
        );
    }

    #[test]
    fn remove_parens_doesnt_apply_precedence() {
        check_assist_not_applicable(remove_parentheses, r#"fn f() { $0(2 + 2) * 8; }"#);
        check_assist_not_applicable(remove_parentheses, r#"fn f() { $0(2 + 2).f(); }"#);
        check_assist_not_applicable(remove_parentheses, r#"fn f() { $0(2 + 2).await; }"#);
        check_assist_not_applicable(remove_parentheses, r#"fn f() { $0!(2..2); }"#);
    }

    #[test]
    fn remove_parens_doesnt_apply_with_cursor_not_on_paren() {
        check_assist_not_applicable(remove_parentheses, r#"fn f() { (2 +$0 2) }"#);
        check_assist_not_applicable(remove_parentheses, r#"fn f() {$0 (2 + 2) }"#);
    }
}