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use crate::{make, Metadata, Report, Rule, Suggestion};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{Pattern, TypedNode},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for an empty variadic pattern: `{...}`, in a function
/// argument.
///
/// ## Why is this bad?
/// The intention with empty patterns is not instantly obvious. Prefer
/// an underscore identifier instead, to indicate that the argument
/// is being ignored.
///
/// ## Example
///
/// ```nix
/// client = { ... }: {
/// imports = [ self.nixosModules.irmaseal-pkg ];
/// services.irmaseal-pkg.enable = true;
/// };
/// ```
///
/// Replace the empty variadic pattern with `_` to indicate that you
/// intend to ignore the argument:
///
/// ```nix
/// client = _: {
/// imports = [ self.nixosModules.irmaseal-pkg ];
/// services.irmaseal-pkg.enable = true;
/// };
/// ```
#[lint(
name = "empty pattern",
note = "Found empty pattern in function argument",
code = 10,
match_with = SyntaxKind::NODE_PATTERN
)]
struct EmptyPattern;
impl Rule for EmptyPattern {
fn validate(&self, node: &SyntaxElement) -> Option<Report> {
if_chain! {
if let NodeOrToken::Node(node) = node;
if let Some(pattern) = Pattern::cast(node.clone());
// no patterns within `{ }`
if pattern.entries().count() == 0;
// pattern is not bound
if pattern.at().is_none();
then {
let at = node.text_range();
let message = "This pattern is empty, use `_` instead";
let replacement = make::ident("_").node().clone();
Some(self.report().suggest(at, message, Suggestion::new(at, replacement)))
} else {
None
}
}
}
}
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