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use crate::{
make,
session::{SessionInfo, Version},
Metadata, Report, Rule, Suggestion,
};
use if_chain::if_chain;
use macros::lint;
use rnix::{
types::{Select, TypedNode},
NodeOrToken, SyntaxElement, SyntaxKind,
};
/// ## What it does
/// Checks for `lib.groupBy`.
///
/// ## Why is this bad?
/// Nix 2.5 introduces `builtins.groupBy` which is faster and does
/// not require a lib import.
///
/// ## Example
///
/// ```nix
/// lib.groupBy (x: if x > 2 then "big" else "small") [ 1 2 3 4 5 6 ];
/// # { big = [ 3 4 5 6 ]; small = [ 1 2 ]; }
/// ```
///
/// Replace `lib.groupBy` with `builtins.groupBy`:
///
/// ```nix
/// builtins.groupBy (x: if x > 2 then "big" else "small") [ 1 2 3 4 5 6 ];
/// ```
#[lint(
name = "faster_groupby",
note = "Found lib.groupBy",
code = 15,
match_with = SyntaxKind::NODE_SELECT
)]
struct FasterGroupBy;
impl Rule for FasterGroupBy {
fn validate(&self, node: &SyntaxElement, sess: &SessionInfo) -> Option<Report> {
let lint_version = "2.5".parse::<Version>().unwrap();
if_chain! {
if sess.version() >= &lint_version;
if let NodeOrToken::Node(node) = node;
if let Some(select_expr) = Select::cast(node.clone());
if let Some(select_from) = select_expr.set();
if let Some(group_by_attr) = select_expr.index();
// a heuristic to lint on nixpkgs.lib.groupBy
// and lib.groupBy and its variants
if select_from.text().to_string() != "builtins";
if group_by_attr.text().to_string() == "groupBy";
then {
let at = node.text_range();
let replacement = {
let builtins = make::ident("builtins");
make::select(builtins.node(), &group_by_attr).node().clone()
};
let message = format!("Prefer `builtins.groupBy` over `{}.groupBy`", select_from);
Some(
self.report()
.suggest(at, message, Suggestion::new(at, replacement)),
)
} else {
None
}
}
}
}
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