feat: Add deprecated_attributes_without_note

Signed-off-by: hashcatHitman <155700084+hashcatHitman@users.noreply.github.com>

Author: hashcatHitman

CHANGELOG.md

@@ -6966,6 +6966,7 @@ Released 2018-09-13
 [`default_trait_access`]: https://rust-lang.github.io/rust-clippy/main/index.html#default_trait_access
 [`default_union_representation`]: https://rust-lang.github.io/rust-clippy/main/index.html#default_union_representation
 [`definition_in_module_root`]: https://rust-lang.github.io/rust-clippy/main/index.html#definition_in_module_root
+[`deprecated_attributes_without_note`]: https://rust-lang.github.io/rust-clippy/main/index.html#deprecated_attributes_without_note
 [`deprecated_attributes_without_since`]: https://rust-lang.github.io/rust-clippy/main/index.html#deprecated_attributes_without_since
 [`deprecated_cfg_attr`]: https://rust-lang.github.io/rust-clippy/main/index.html#deprecated_cfg_attr
 [`deprecated_clippy_cfg_attr`]: https://rust-lang.github.io/rust-clippy/main/index.html#deprecated_clippy_cfg_attr

clippy_lints/src/attrs/deprecated_attributes_without_note.rs

@@ -0,0 +1,36 @@
+use super::{Attribute, DEPRECATED_ATTRIBUTES_WITHOUT_NOTE};
+use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::is_from_proc_macro;
+use rustc_ast::{MetaItemInner, MetaItemKind};
+use rustc_lint::{EarlyContext, LintContext as _};
+use rustc_span::sym;
+
+pub(super) fn check<'cx>(cx: &EarlyContext<'cx>, items: Option<&[MetaItemInner]>, attr: &'cx Attribute) {
+    // Check if a note is present
+    if let Some(items) = items {
+        for item_inner in items {
+            if let Some(item) = MetaItemInner::meta_item(item_inner)
+                && let MetaItemKind::NameValue(_) = &item.kind
+                && item.path == sym::note
+            {
+                return;
+            }
+        }
+    }
+
+    // Check if the attribute is in an external macro and therefore out of the developer's control
+    if attr.span.in_external_macro(cx.sess().source_map()) || is_from_proc_macro(cx, attr) {
+        return;
+    }
+
+    #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
+    span_lint_and_then(
+        cx,
+        DEPRECATED_ATTRIBUTES_WITHOUT_NOTE,
+        attr.span,
+        "`deprecated` attribute without note",
+        |diag| {
+            diag.help("try adding a note at the end with `#[deprecated(note = \"..\", ..)]`");
+        },
+    );
+}

clippy_lints/src/attrs/mod.rs

@@ -1,6 +1,7 @@
 mod allow_attributes;
 mod allow_attributes_without_reason;
 mod blanket_clippy_restriction_lints;
+mod deprecated_attributes_without_note;
 mod deprecated_attributes_without_since;
 mod deprecated_cfg_attr;
 mod deprecated_semver;
@@ -106,6 +107,28 @@ declare_clippy_lint! {
     "enabling the complete restriction group"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for attributes that deprecate items without a `note` field.
+    ///
+    /// ### Why restrict this?
+    /// This is typically used to provide an explanation about the deprecation
+    /// and preferred alternatives.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// #[deprecated]
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// #[deprecated(note = "foo was rarely used. Users should instead use bar")]
+    /// ```
+    #[clippy::version = "1.100.0"]
+    pub DEPRECATED_ATTRIBUTES_WITHOUT_NOTE,
+    restriction,
+    "ensures that all `deprecated` attributes have a `note` field"
+}
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for attributes that deprecate items without a `since` field.
@@ -504,6 +527,7 @@ declare_clippy_lint! {
 }
 
 impl_lint_pass!(Attributes => [
+    DEPRECATED_ATTRIBUTES_WITHOUT_NOTE,
     DEPRECATED_ATTRIBUTES_WITHOUT_SINCE,
     INLINE_ALWAYS,
     REPR_PACKED_WITHOUT_ABI,
@@ -618,6 +642,7 @@ impl EarlyLintPass for PostExpansionEarlyAttributes {
             }
             if matches!(name, sym::deprecated) {
                 deprecated_attributes_without_since::check(cx, Some(items), attr);
+                deprecated_attributes_without_note::check(cx, Some(items), attr);
             }
             if is_lint_level(name) {
                 blanket_clippy_restriction_lints::check(cx, name, items);
@@ -634,6 +659,11 @@ impl EarlyLintPass for PostExpansionEarlyAttributes {
                 }
             }
         } else if attr.has_name(sym::deprecated) {
+            if let AttrKind::Normal(normal_attr) = &attr.kind
+                && !matches!(normal_attr.item.args, AttrArgs::Eq { .. })
+            {
+                deprecated_attributes_without_note::check(cx, None, attr);
+            }
             deprecated_attributes_without_since::check(cx, None, attr);
         }
 

clippy_lints/src/declared_lints.rs

@@ -19,6 +19,7 @@ pub static LINTS: &[&::declare_clippy_lint::LintInfo] = &[
     crate::attrs::ALLOW_ATTRIBUTES_INFO,
     crate::attrs::ALLOW_ATTRIBUTES_WITHOUT_REASON_INFO,
     crate::attrs::BLANKET_CLIPPY_RESTRICTION_LINTS_INFO,
+    crate::attrs::DEPRECATED_ATTRIBUTES_WITHOUT_NOTE_INFO,
     crate::attrs::DEPRECATED_ATTRIBUTES_WITHOUT_SINCE_INFO,
     crate::attrs::DEPRECATED_CFG_ATTR_INFO,
     crate::attrs::DEPRECATED_CLIPPY_CFG_ATTR_INFO,

tests/ui/deprecated_attributes_without_note.rs

@@ -0,0 +1,46 @@
+//@aux-build:proc_macros.rs
+#![deny(clippy::deprecated_attributes_without_note)]
+
+extern crate proc_macros;
+use proc_macros::{external, with_span};
+
+// These should trigger the lint
+#[deprecated]
+//~^ deprecated_attributes_without_note
+fn foo() {}
+
+#[deprecated(since = "1.42.100")]
+//~^ deprecated_attributes_without_note
+fn quux() {}
+
+// These should be fine
+#[allow(deprecated)]
+#[allow(dead_code, reason = "This should be allowed")]
+#[expect(dead_code)]
+#[warn(dyn_drop, reason = "Warnings can also have reasons")]
+#[warn(deref_nullptr)]
+#[deny(deref_nullptr)]
+#[forbid(deref_nullptr)]
+fn main() {
+    external! {
+        #[deprecated]
+        fn a() {}
+    }
+    with_span! {
+        span
+        #[deprecated]
+        fn b() {}
+    }
+}
+
+#[deprecated(since = "TBD", note = "use qux instead")]
+fn baz() {}
+
+#[deprecated(note = "use quux instead", since = "0.0.1")]
+fn qux() {}
+
+#[deprecated(note = "I don't feel like maintaining this anymore, sorry")]
+fn bar() {}
+
+#[deprecated = "probably a bad idea to use this"]
+fn weird() {}

tests/ui/deprecated_attributes_without_note.stderr

@@ -0,0 +1,23 @@
+error: `deprecated` attribute without note
+  --> tests/ui/deprecated_attributes_without_note.rs:8:1
+   |
+LL | #[deprecated]
+   | ^^^^^^^^^^^^^
+   |
+   = help: try adding a note at the end with `#[deprecated(note = "..", ..)]`
+note: the lint level is defined here
+  --> tests/ui/deprecated_attributes_without_note.rs:2:9
+   |
+LL | #![deny(clippy::deprecated_attributes_without_note)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: `deprecated` attribute without note
+  --> tests/ui/deprecated_attributes_without_note.rs:12:1
+   |
+LL | #[deprecated(since = "1.42.100")]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: try adding a note at the end with `#[deprecated(note = "..", ..)]`
+
+error: aborting due to 2 previous errors
+