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use clippy_config::Conf;
use clippy_utils::diagnostics::span_lint;
use clippy_utils::source::snippet_opt;
use rustc_data_structures::fx::FxHashSet;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
use rustc_hir::{HirId, ItemKind, Node, Path};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::impl_lint_pass;
use rustc_span::symbol::kw;
declare_clippy_lint! {
/// ### What it does
/// Checks for usage of items through absolute paths, like `std::env::current_dir`.
///
/// ### Why restrict this?
/// Many codebases have their own style when it comes to importing, but one that is seldom used
/// is using absolute paths *everywhere*. This is generally considered unidiomatic, and you
/// should add a `use` statement.
///
/// The default maximum segments (2) is pretty strict, you may want to increase this in
/// `clippy.toml`.
///
/// Note: One exception to this is code from macro expansion - this does not lint such cases, as
/// using absolute paths is the proper way of referencing items in one.
///
/// ### Example
/// ```no_run
/// let x = std::f64::consts::PI;
/// ```
/// Use any of the below instead, or anything else:
/// ```no_run
/// use std::f64;
/// use std::f64::consts;
/// use std::f64::consts::PI;
/// let x = f64::consts::PI;
/// let x = consts::PI;
/// let x = PI;
/// use std::f64::consts as f64_consts;
/// let x = f64_consts::PI;
/// ```
#[clippy::version = "1.73.0"]
pub ABSOLUTE_PATHS,
restriction,
"checks for usage of an item without a `use` statement"
}
impl_lint_pass!(AbsolutePaths => [ABSOLUTE_PATHS]);
pub struct AbsolutePaths {
pub absolute_paths_max_segments: u64,
pub absolute_paths_allowed_crates: &'static FxHashSet<String>,
}
impl AbsolutePaths {
pub fn new(conf: &'static Conf) -> Self {
Self {
absolute_paths_max_segments: conf.absolute_paths_max_segments,
absolute_paths_allowed_crates: &conf.absolute_paths_allowed_crates,
}
}
}
impl LateLintPass<'_> for AbsolutePaths {
// We should only lint `QPath::Resolved`s, but since `Path` is only used in `Resolved` and `UsePath`
// we don't need to use a visitor or anything as we can just check if the `Node` for `hir_id` isn't
// a `Use`
#[expect(clippy::cast_possible_truncation)]
fn check_path(&mut self, cx: &LateContext<'_>, path: &Path<'_>, hir_id: HirId) {
let Self {
absolute_paths_max_segments,
absolute_paths_allowed_crates,
} = self;
if !path.span.from_expansion()
&& let node = cx.tcx.hir_node(hir_id)
&& !matches!(node, Node::Item(item) if matches!(item.kind, ItemKind::Use(_, _)))
&& let [first, rest @ ..] = path.segments
// Handle `::std`
&& let (segment, len) = if first.ident.name == kw::PathRoot {
// Indexing is fine as `PathRoot` must be followed by another segment. `len() - 1`
// is fine here for the same reason
(&rest[0], path.segments.len() - 1)
} else {
(first, path.segments.len())
}
&& len > *absolute_paths_max_segments as usize
&& let Some(segment_snippet) = snippet_opt(cx, segment.ident.span)
&& segment_snippet == segment.ident.as_str()
{
let is_abs_external =
matches!(segment.res, Res::Def(DefKind::Mod, DefId { index, .. }) if index == CRATE_DEF_INDEX);
let is_abs_crate = segment.ident.name == kw::Crate;
if is_abs_external && absolute_paths_allowed_crates.contains(segment.ident.name.as_str())
|| is_abs_crate && absolute_paths_allowed_crates.contains("crate")
{
return;
}
if is_abs_external || is_abs_crate {
span_lint(
cx,
ABSOLUTE_PATHS,
path.span,
"consider bringing this path into scope with the `use` keyword",
);
}
}
}
}
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