Empty docs

CHANGELOG.md

@@ -5158,6 +5158,7 @@ Released 2018-09-13
 [`duration_subsec`]: https://rust-lang.github.io/rust-clippy/master/index.html#duration_subsec
 [`eager_transmute`]: https://rust-lang.github.io/rust-clippy/master/index.html#eager_transmute
 [`else_if_without_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#else_if_without_else
+[`empty_docs`]: https://rust-lang.github.io/rust-clippy/master/index.html#empty_docs
 [`empty_drop`]: https://rust-lang.github.io/rust-clippy/master/index.html#empty_drop
 [`empty_enum`]: https://rust-lang.github.io/rust-clippy/master/index.html#empty_enum
 [`empty_enum_variants_with_brackets`]: https://rust-lang.github.io/rust-clippy/master/index.html#empty_enum_variants_with_brackets

clippy_lints/src/declared_lints.rs

@@ -139,6 +139,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::disallowed_types::DISALLOWED_TYPES_INFO,
     crate::doc::DOC_LINK_WITH_QUOTES_INFO,
     crate::doc::DOC_MARKDOWN_INFO,
+    crate::doc::EMPTY_DOCS_INFO,
     crate::doc::MISSING_ERRORS_DOC_INFO,
     crate::doc::MISSING_PANICS_DOC_INFO,
     crate::doc::MISSING_SAFETY_DOC_INFO,

clippy_lints/src/doc/empty_docs.rs

@@ -0,0 +1,25 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use rustc_ast::Attribute;
+use rustc_lint::LateContext;
+
+use super::EMPTY_DOCS;
+
+// TODO: Adjust the parameters as necessary
+pub(super) fn check(cx: &LateContext<'_>, attrs: &[Attribute]) {
+    let doc_attrs: Vec<_> = attrs.iter().filter(|attr| attr.doc_str().is_some()).collect();
+
+    let span;
+    if let Some(first) = doc_attrs.first()
+        && let Some(last) = doc_attrs.last()
+    {
+        span = first.span.with_hi(last.span.hi());
+        span_lint_and_help(
+            cx,
+            EMPTY_DOCS,
+            span,
+            "empty doc comment",
+            None,
+            "consider removing or filling it",
+        );
+    }
+}

clippy_lints/src/doc/mod.rs

@@ -27,6 +27,7 @@ use rustc_span::{sym, Span};
 use std::ops::Range;
 use url::Url;
 
+mod empty_docs;
 mod link_with_quotes;
 mod markdown;
 mod missing_headers;
@@ -338,6 +339,29 @@ declare_clippy_lint! {
     "suspicious usage of (outer) doc comments"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Detects documentation that is empty.
+    /// ### Why is this bad?
+    /// It is unlikely that there is any reason to have empty documentation for an item
+    /// ### Example
+    /// ```rust
+    /// ///
+    /// fn returns_true() -> bool {
+    ///     true
+    /// }
+    /// Use instead:
+    /// ```rust
+    /// fn returns_true() -> bool {
+    ///     true
+    /// }
+    /// ```
+    #[clippy::version = "1.78.0"]
+    pub EMPTY_DOCS,
+    suspicious,
+    "docstrings exist but documentation is empty"
+}
+
 #[derive(Clone)]
 pub struct Documentation {
     valid_idents: FxHashSet<String>,
@@ -364,7 +388,8 @@ impl_lint_pass!(Documentation => [
     NEEDLESS_DOCTEST_MAIN,
     TEST_ATTR_IN_DOCTEST,
     UNNECESSARY_SAFETY_DOC,
-    SUSPICIOUS_DOC_COMMENTS
+    SUSPICIOUS_DOC_COMMENTS,
+    EMPTY_DOCS,
 ]);
 
 impl<'tcx> LateLintPass<'tcx> for Documentation {
@@ -378,6 +403,11 @@ impl<'tcx> LateLintPass<'tcx> for Documentation {
         let Some(headers) = check_attrs(cx, &self.valid_idents, attrs) else {
             return;
         };
+
+        if headers.empty && !item.span.is_dummy() {
+            empty_docs::check(cx, attrs);
+        }
+
         match item.kind {
             hir::ItemKind::Fn(ref sig, _, body_id) => {
                 if !(is_entrypoint_fn(cx, item.owner_id.to_def_id()) || in_external_macro(cx.tcx.sess, item.span)) {
@@ -477,6 +507,7 @@ struct DocHeaders {
     safety: bool,
     errors: bool,
     panics: bool,
+    empty: bool,
 }
 
 /// Does some pre-processing on raw, desugared `#[doc]` attributes such as parsing them and
@@ -502,14 +533,21 @@ fn check_attrs(cx: &LateContext<'_>, valid_idents: &FxHashSet<String>, attrs: &[
     suspicious_doc_comments::check(cx, attrs);
 
     let (fragments, _) = attrs_to_doc_fragments(attrs.iter().map(|attr| (attr, None)), true);
-    let mut doc = String::new();
-    for fragment in &fragments {
-        add_doc_fragment(&mut doc, fragment);
-    }
+    let mut doc = fragments
+        .iter()
+        .fold(String::new(), |mut acc, fragment| {
+            add_doc_fragment(&mut acc, fragment);
+            acc
+        })
+        .trim()
+        .to_string();
     doc.pop();
 
     if doc.is_empty() {
-        return Some(DocHeaders::default());
+        return Some(DocHeaders {
+            empty: true,
+            ..DocHeaders::default()
+        });
     }
 
     let mut cb = fake_broken_link_callback;

tests/ui/empty_docs.rs

@@ -0,0 +1,61 @@
+#![allow(unused)]
+#![warn(clippy::empty_docs)]
+
+/// this is a struct
+struct Bananas {
+    /// count
+    count: usize,
+}
+
+///
+enum Warn {
+    ///
+    A,
+    ///
+    B,
+}
+
+enum WarnA {
+    ///
+    A,
+    B,
+}
+
+enum DontWarn {
+    /// it's ok
+    A,
+    ///
+    B,
+}
+
+#[doc = ""]
+fn warn_about_this() {}
+
+#[doc = ""]
+#[doc = ""]
+fn this_doesn_warn() {}
+
+#[doc = "a fine function"]
+fn this_is_fine() {}
+
+fn warn_about_this_as_well() {
+    //!
+}
+
+///
+fn warn_inner_outer() {
+    //! what
+}
+
+fn this_is_ok() {
+    //!
+    //! inside the function
+}
+
+fn warn() {
+    /*! */
+}
+
+fn dont_warn() {
+    /*! dont warn me */
+}

tests/ui/empty_docs.stderr

@@ -0,0 +1,45 @@
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:10:1
+   |
+LL | ///
+   | ^^^
+   |
+   = help: consider removing or filling it
+   = note: `-D clippy::empty-docs` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::empty_docs)]`
+
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:31:1
+   |
+LL | #[doc = ""]
+   | ^^^^^^^^^^^
+   |
+   = help: consider removing or filling it
+
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:34:1
+   |
+LL | / #[doc = ""]
+LL | | #[doc = ""]
+   | |___________^
+   |
+   = help: consider removing or filling it
+
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:42:5
+   |
+LL |     //!
+   |     ^^^
+   |
+   = help: consider removing or filling it
+
+error: empty doc comment
+  --> tests/ui/empty_docs.rs:56:5
+   |
+LL |     /*! */
+   |     ^^^^^^
+   |
+   = help: consider removing or filling it
+
+error: aborting due to 5 previous errors
+