use crate::{session::SessionInfo, Diagnostic, Metadata, Report, Rule, Suggestion}; use if_chain::if_chain; use macros::lint; use rnix::{ types::{KeyValue, LetIn, Paren, ParsedType, TypedNode, Wrapper}, NodeOrToken, SyntaxElement, SyntaxKind, }; /// ## What it does /// Checks for unnecessary parentheses. /// /// ## Why is this bad? /// Unnecessarily parenthesized code is hard to read. /// /// ## Example /// /// ```nix /// let /// double = (x: 2 * x); /// ls = map (double) [ 1 2 3 ]; /// in /// (2 + 3) /// ``` /// /// Remove unnecessary parentheses: /// /// ```nix /// let /// double = x: 2 * x; /// ls = map double [ 1 2 3 ]; /// in /// 2 + 3 /// ``` #[lint( name = "useless_parens", note = "These parentheses can be omitted", code = 8, match_with = [ SyntaxKind::NODE_KEY_VALUE, SyntaxKind::NODE_PAREN, SyntaxKind::NODE_LET_IN, ] )] struct UselessParens; impl Rule for UselessParens { fn validate(&self, node: &SyntaxElement, _sess: &SessionInfo) -> Option<Report> { if_chain! { if let NodeOrToken::Node(node) = node; if let Some(parsed_type_node) = ParsedType::cast(node.clone()); if let Some(diagnostic) = do_thing(parsed_type_node); then { let mut report = self.report(); report.diagnostics.push(diagnostic); Some(report) } else { None } } } } fn do_thing(parsed_type_node: ParsedType) -> Option<Diagnostic> { match parsed_type_node { ParsedType::KeyValue(kv) => if_chain! { if let Some(value_node) = kv.value(); let value_range = value_node.text_range(); if let Some(value_in_parens) = Paren::cast(value_node); if let Some(inner) = value_in_parens.inner(); then { let at = value_range; let message = "Useless parentheses around value in binding"; let replacement = inner; Some(Diagnostic::suggest(at, message, Suggestion::new(at, replacement))) } else { None } }, ParsedType::LetIn(let_in) => if_chain! { if let Some(body_node) = let_in.body(); let body_range = body_node.text_range(); if let Some(body_as_parens) = Paren::cast(body_node); if let Some(inner) = body_as_parens.inner(); then { let at = body_range; let message = "Useless parentheses around body of `let` expression"; let replacement = inner; Some(Diagnostic::suggest(at, message, Suggestion::new(at, replacement))) } else { None } }, ParsedType::Paren(paren_expr) => if_chain! { let paren_expr_range = paren_expr.node().text_range(); if let Some(father_node) = paren_expr.node().parent(); // ensure that we don't lint inside let-in statements // we already lint such cases in previous match stmt if KeyValue::cast(father_node.clone()).is_none(); // ensure that we don't lint inside let-bodies // if this primitive is a let-body, we have already linted it if LetIn::cast(father_node).is_none(); if let Some(inner_node) = paren_expr.inner(); if let Some(parsed_inner) = ParsedType::cast(inner_node); if matches!( parsed_inner, ParsedType::List(_) | ParsedType::Paren(_) | ParsedType::Str(_) | ParsedType::AttrSet(_) | ParsedType::Select(_) | ParsedType::Ident(_) ); then { let at = paren_expr_range; let message = "Useless parentheses around primitive expression"; let replacement = parsed_inner.node().clone(); Some(Diagnostic::suggest(at, message, Suggestion::new(at, replacement))) } else { None } }, _ => None, } }