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use crate::{make, Metadata, Report, Rule, Suggestion};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{Apply, Ident, TokenWrapper, TypedNode},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for usage of the `isNull` function.
///
/// ## Why is this bad?
/// `isNull` is deprecated.
///
/// ## Example
///
/// Instead of `isNull` for `null` checks,
///
/// ```nix
/// isNull e
/// ```
///
/// use the equality operator:
///
/// ```nix
/// e == null
/// ```
#[lint(
name = "deprecated_is_null",
note = "Found usage of deprecated builtin isNull",
code = 13,
match_with = SyntaxKind::NODE_APPLY
)]
struct DeprecatedIsNull;
impl Rule for DeprecatedIsNull {
fn validate(&self, node: &SyntaxElement) -> Option<Report> {
if_chain! {
if let NodeOrToken::Node(node) = node;
if let Some(apply) = Apply::cast(node.clone());
if let Some(ident) = Ident::cast(apply.lambda()?);
if ident.as_str() == "isNull";
if let Some(value) = apply.value();
then {
let null = make::ident("null");
let binop = make::binary(&value, "==", null.node());
let parenthesized = make::parenthesize(binop.node());
let at = node.text_range();
let replacement = parenthesized.node().clone();
let message = "`isNull` is deprecated, check equality with `null` instead";
Some(self.report().suggest(at, message, Suggestion::new(at, replacement)))
} else {
None
}
}
}
}
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