new lint: use_crate_prefix_for_self_imports

CHANGELOG.md

@@ -6940,6 +6940,7 @@ Released 2018-09-13
 [`unwrap_or_else_default`]: https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_or_else_default
 [`unwrap_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#unwrap_used
 [`upper_case_acronyms`]: https://rust-lang.github.io/rust-clippy/master/index.html#upper_case_acronyms
+[`use_crate_prefix_for_self_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#use_crate_prefix_for_self_imports
 [`use_debug`]: https://rust-lang.github.io/rust-clippy/master/index.html#use_debug
 [`use_self`]: https://rust-lang.github.io/rust-clippy/master/index.html#use_self
 [`used_underscore_binding`]: https://rust-lang.github.io/rust-clippy/master/index.html#used_underscore_binding

clippy_lints/src/declared_lints.rs

@@ -774,6 +774,7 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::unwrap::UNNECESSARY_UNWRAP_INFO,
     crate::unwrap_in_result::UNWRAP_IN_RESULT_INFO,
     crate::upper_case_acronyms::UPPER_CASE_ACRONYMS_INFO,
+    crate::use_crate_prefix_for_self_imports::USE_CRATE_PREFIX_FOR_SELF_IMPORTS_INFO,
     crate::use_self::USE_SELF_INFO,
     crate::useless_concat::USELESS_CONCAT_INFO,
     crate::useless_conversion::USELESS_CONVERSION_INFO,

clippy_lints/src/lib.rs

@@ -394,6 +394,7 @@ mod unused_unit;
 mod unwrap;
 mod unwrap_in_result;
 mod upper_case_acronyms;
+mod use_crate_prefix_for_self_imports;
 mod use_self;
 mod useless_concat;
 mod useless_conversion;
@@ -834,5 +835,8 @@ pub fn register_lint_passes(store: &mut rustc_lint::LintStore, conf: &'static Co
     store.register_late_pass(|_| Box::new(toplevel_ref_arg::ToplevelRefArg));
     store.register_late_pass(|_| Box::new(volatile_composites::VolatileComposites));
     store.register_late_pass(|_| Box::new(replace_box::ReplaceBox));
+    store.register_late_pass(|_| {
+        Box::<use_crate_prefix_for_self_imports::UseCratePrefixForSelfImports<'_, '_>>::default()
+    });
     // add lints here, do not remove this comment, it's used in `new_lint`
 }

clippy_lints/src/use_crate_prefix_for_self_imports.rs

@@ -0,0 +1,156 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::SpanRangeExt;
+use clippy_utils::tokenize_with_text;
+use def_id::LOCAL_CRATE;
+use rustc_data_structures::fx::FxHashSet;
+use rustc_errors::Applicability;
+use rustc_hir::def::Res;
+use rustc_hir::{Item, ItemKind, UsePath, def_id};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_session::impl_lint_pass;
+use rustc_span::{FileName, RealFileName, Span, Symbol, kw};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// This lint checks for imports from the current crate that do not use the `crate::` prefix.
+    /// It suggests using `crate::` to make it clear that the item is from the same crate.
+    ///
+    /// ### Why is this bad?
+    /// When imports from the current crate lack the `crate::` prefix, it can make the code less readable
+    /// because it’s not immediately clear if the imported item is from the current crate or an external dependency.
+    /// Using `crate::` for self-imports provides a consistent style, making the origin of each import clear.
+    /// This helps reduce confusion and maintain a uniform codebase.
+    ///
+    /// ### Example
+    /// ```rust,ignore
+    /// // lib.rs
+    /// mod foo;
+    /// use foo::bar;
+    /// ```
+    ///
+    /// ```rust,ignore
+    /// // foo.rs
+    /// #[path = "./foo.rs"]
+    /// pub fn bar() {}
+    /// ```
+    ///
+    /// Use instead:
+    /// ```rust,ignore
+    /// // lib.rs
+    /// mod foo;
+    /// use crate::foo::bar;
+    /// ```
+    ///
+    /// ```rust,ignore
+    /// // foo.rs
+    /// #[path = "./foo.rs"]
+    /// pub fn bar() {}
+    /// ```
+    #[clippy::version = "1.92.0"]
+    pub USE_CRATE_PREFIX_FOR_SELF_IMPORTS,
+    nursery,
+    "checks that imports from the current crate use the `crate::` prefix"
+}
+
+#[derive(Clone, Default)]
+pub struct UseCratePrefixForSelfImports<'a, 'tcx> {
+    /// collect `use` in current block
+    use_block: Vec<&'a UsePath<'tcx>>,
+    /// collect `mod` in current block
+    mod_names: FxHashSet<Symbol>,
+    latest_span: Option<Span>,
+}
+
+impl_lint_pass!(UseCratePrefixForSelfImports<'_, '_> => [USE_CRATE_PREFIX_FOR_SELF_IMPORTS]);
+
+impl<'a, 'tcx> LateLintPass<'tcx> for UseCratePrefixForSelfImports<'a, 'tcx> {
+    fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'a Item<'tcx>) {
+        let FileName::Real(RealFileName::LocalPath(p)) = cx.sess().source_map().span_to_filename(item.span) else {
+            self.clear();
+            return;
+        };
+        let Some(file_name) = p.file_name() else {
+            self.clear();
+            return;
+        };
+        // only check `main.rs` and `lib.rs`
+        if !(file_name == "main.rs" || file_name == "lib.rs") {
+            return;
+        }
+
+        self.insert_item(cx, item);
+    }
+}
+
+impl<'tcx> UseCratePrefixForSelfImports<'_, 'tcx> {
+    fn in_same_block(&self, cx: &LateContext<'tcx>, span: Span) -> bool {
+        match self.latest_span {
+            Some(latest_span) => {
+                if latest_span.contains(span) {
+                    return true;
+                }
+                let gap_span = latest_span.between(span);
+                let gap_snippet = gap_span.get_source_text(cx).unwrap();
+                for (token, source, _) in tokenize_with_text(&gap_snippet) {
+                    if token == rustc_lexer::TokenKind::Whitespace && source.chars().filter(|c| *c == '\n').count() > 1
+                    {
+                        return false;
+                    }
+                }
+                true
+            },
+            None => true,
+        }
+    }
+
+    fn insert_item(&mut self, cx: &LateContext<'tcx>, item: &Item<'tcx>) {
+        if item.span.from_expansion() {
+            return;
+        }
+        if !self.in_same_block(cx, item.span) {
+            self.try_lint(cx);
+            self.clear();
+        }
+        match item.kind {
+            ItemKind::Mod(ident, _) => {
+                self.mod_names.insert(ident.name);
+            },
+            ItemKind::Use(use_tree, _) => {
+                self.use_block.push(use_tree);
+            },
+            _ => {},
+        }
+        self.latest_span = match self.latest_span {
+            Some(latest_span) => Some(latest_span.with_hi(item.span.hi())),
+            None => Some(item.span),
+        };
+    }
+
+    fn try_lint(&self, cx: &LateContext<'tcx>) {
+        for use_path in &self.use_block {
+            if let [segment, ..] = &use_path.segments
+                && let Res::Def(_, def_id) = segment.res
+                && def_id.krate == LOCAL_CRATE
+            {
+                let root = segment.ident.name;
+                if !matches!(root, kw::Crate | kw::Super | kw::SelfLower) && !self.mod_names.contains(&root) {
+                    span_lint_and_sugg(
+                        cx,
+                        USE_CRATE_PREFIX_FOR_SELF_IMPORTS,
+                        segment.ident.span,
+                        "this import is not clear",
+                        "prefix with `crate::`",
+                        format!("crate::{root}"),
+                        Applicability::MachineApplicable,
+                    );
+                }
+            }
+        }
+    }
+
+    fn clear(&mut self) {
+        self.use_block.clear();
+        self.mod_names.clear();
+        self.latest_span = None;
+    }
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/fail/Cargo.stderr

@@ -0,0 +1,10 @@
+error: this import is not clear
+ --> src/main.rs:3:5
+  |
+3 | use foo::Foo;
+  |     ^^^ help: prefix with `crate::`: `crate::foo`
+  |
+  = note: `-D clippy::use-crate-prefix-for-self-imports` implied by `-D warnings`
+  = help: to override `-D warnings` add `#[allow(clippy::use_crate_prefix_for_self_imports)]`
+
+error: could not compile `fail` (bin "fail") due to 1 previous error

tests/ui-cargo/use_crate_prefix_for_self_imports/fail/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "fail"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/fail/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/fail/src/main.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+use foo::Foo;
+
+mod foo;
+
+fn main() {
+    let _foo = Foo;
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/pass/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass/src/main.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+use crate::foo::Foo;
+
+mod foo;
+
+fn main() {
+    let _foo = Foo;
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "pass_attribute"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]
+
+[features]
+default = ["bar"]
+bar = []

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute/src/lib.rs

@@ -0,0 +1,6 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+#[cfg(feature = "bar")]
+mod foo;
+#[cfg(feature = "bar")]
+pub use foo::Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute_2/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass_attribute_2"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute_2/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_attribute_2/src/lib.rs

@@ -0,0 +1,5 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+mod foo;
+#[doc(hidden)]
+pub use foo::Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_2/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass_sibling_2"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_2/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_2/src/main.rs

@@ -0,0 +1,8 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+use foo::Foo;
+mod foo;
+
+fn main() {
+    let _foo = Foo;
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_3/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass_sibling_3"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_3/src/foo.rs

@@ -0,0 +1,2 @@
+pub struct Foo;
+pub struct Bar;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_3/src/main.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+mod foo;
+pub use foo::{Bar, Foo};
+
+fn main() {
+    let _foo = Foo;
+    let _bar = Bar;
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_4/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass_sibling_4"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_4/src/foo.rs

@@ -0,0 +1,2 @@
+pub struct Foo;
+pub struct Bar;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_4/src/main.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+pub use foo::{Bar, Foo};
+mod foo;
+
+fn main() {
+    let _foo = Foo;
+    let _bar = Bar;
+}

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_comment/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "pass_sibling_comment"
+version = "0.1.0"
+edition = "2024"
+publish = false
+
+[dependencies]

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_comment/src/foo.rs

@@ -0,0 +1 @@
+pub struct Foo;

tests/ui-cargo/use_crate_prefix_for_self_imports/pass_sibling_comment/src/main.rs

@@ -0,0 +1,9 @@
+#![warn(clippy::use_crate_prefix_for_self_imports)]
+
+mod foo;
+// some comments here
+use foo::Foo;
+
+fn main() {
+    let _foo = Foo;
+}