Add new lint doc_overindented_list_item

Add a new lint `doc_overindented_list_item` to detect and fix list items
in docs that are overindented.

For example,

```rs
/// - first line
///      second line
fn foo() {}
```

this would be fixed to:

```rs
/// - first line
///   second line
fn foo() {}
```

This lint improves readabiliy and consistency in doc.

Author: ohno418

CHANGELOG.md

@@ -5492,6 +5492,7 @@ Released 2018-09-13
 [`doc_link_with_quotes`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_link_with_quotes
 [`doc_markdown`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_markdown
 [`doc_nested_refdefs`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_nested_refdefs
+[`doc_overindented_list_item`]: https://rust-lang.github.io/rust-clippy/master/index.html#doc_overindented_list_item
 [`double_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#double_comparisons
 [`double_must_use`]: https://rust-lang.github.io/rust-clippy/master/index.html#double_must_use
 [`double_neg`]: https://rust-lang.github.io/rust-clippy/master/index.html#double_neg

README.md

@@ -159,11 +159,11 @@ line. (You can swap `clippy::all` with the specific lint category you are target
 You can add options to your code to `allow`/`warn`/`deny` Clippy lints:
 
 * the whole set of `Warn` lints using the `clippy` lint group (`#![deny(clippy::all)]`).
-    Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).
+  Note that `rustc` has additional [lint groups](https://doc.rust-lang.org/rustc/lints/groups.html).
 
 * all lints using both the `clippy` and `clippy::pedantic` lint groups (`#![deny(clippy::all)]`,
-    `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
-    lints prone to false positives.
+  `#![deny(clippy::pedantic)]`). Note that `clippy::pedantic` contains some very aggressive
+  lints prone to false positives.
 
 * only some lints (`#![deny(clippy::single_match, clippy::box_vec)]`, etc.)
 

clippy_lints/src/declared_lints.rs

@@ -142,6 +142,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::doc::DOC_LINK_WITH_QUOTES_INFO,
     crate::doc::DOC_MARKDOWN_INFO,
     crate::doc::DOC_NESTED_REFDEFS_INFO,
+    crate::doc::DOC_OVERINDENTED_LIST_ITEM_INFO,
     crate::doc::EMPTY_DOCS_INFO,
     crate::doc::EMPTY_LINE_AFTER_DOC_COMMENTS_INFO,
     crate::doc::EMPTY_LINE_AFTER_OUTER_ATTR_INFO,

clippy_lints/src/doc/mod.rs

@@ -1,6 +1,7 @@
 #![allow(clippy::lint_without_lint_pass)]
 
 mod lazy_continuation;
+mod overindented_list_item;
 mod too_long_first_doc_paragraph;
 
 use clippy_config::Conf;
@@ -429,6 +430,39 @@ declare_clippy_lint! {
     "require every line of a paragraph to be indented and marked"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    ///
+    /// Detects overindented list items in doc comments where the continuation
+    /// lines are indented more than necessary.
+    ///
+    /// ### Why is this bad?
+    ///
+    /// Overindented list items in doc comments can lead to inconsistent and
+    /// poorly formatted documentation when rendered. Excessive indentation may
+    /// cause the text to be misinterpreted as a nested list item or code block,
+    /// affecting readability and the overall structure of the documentation.
+    ///
+    /// ### Example
+    ///
+    /// ```no_run
+    /// /// - This is the first item in a list
+    /// ///      and this line is overindented.
+    /// # fn foo() {}
+    /// ```
+    ///
+    /// Fixes this into:
+    /// ```no_run
+    /// /// - This is the first item in a list
+    /// ///   and this line is overindented.
+    /// # fn foo() {}
+    /// ```
+    #[clippy::version = "1.80.0"]
+    pub DOC_OVERINDENTED_LIST_ITEM,
+    style,
+    "ensure list items are not overindented"
+}
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks if the first paragraph in the documentation of items listed in the module page is too long.
@@ -618,6 +652,7 @@ impl_lint_pass!(Documentation => [
     SUSPICIOUS_DOC_COMMENTS,
     EMPTY_DOCS,
     DOC_LAZY_CONTINUATION,
+    DOC_OVERINDENTED_LIST_ITEM,
     EMPTY_LINE_AFTER_OUTER_ATTR,
     EMPTY_LINE_AFTER_DOC_COMMENTS,
     TOO_LONG_FIRST_DOC_PARAGRAPH,
@@ -1004,11 +1039,19 @@ fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize
                     && !in_footnote_definition
                     && !matches!(next_event, End(_))
                 {
+                    let span = Span::new(span.hi(), next_span.lo(), span.ctxt(), span.parent());
                     lazy_continuation::check(
                         cx,
                         doc,
                         range.end..next_range.start,
-                        Span::new(span.hi(), next_span.lo(), span.ctxt(), span.parent()),
+                        span,
+                        &containers[..],
+                    );
+                    overindented_list_item::check(
+                        cx,
+                        doc,
+                        range.end..next_range.start,
+                        span,
                         &containers[..],
                     );
                 }

clippy_lints/src/doc/overindented_list_item.rs

@@ -0,0 +1,51 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use itertools::Itertools;
+use rustc_errors::Applicability;
+use rustc_lint::LateContext;
+use rustc_span::Span;
+use std::ops::Range;
+
+use super::DOC_OVERINDENTED_LIST_ITEM;
+
+pub(super) fn check(cx: &LateContext<'_>, doc: &str, range: Range<usize>, span: Span, containers: &[super::Container]) {
+    if doc[range.clone()].contains('\t') {
+        // We don't do tab stops correctly.
+        return;
+    }
+
+    let is_blockquote = containers.iter().any(|c| matches!(c, super::Container::Blockquote));
+    if is_blockquote {
+        // If this doc is a blockquote, we don't go further.
+        return;
+    }
+
+    let leading_spaces = doc[range].chars().filter(|c| *c == ' ').count();
+    let list_indentation = containers
+        .iter()
+        .map(|c| {
+            if let super::Container::List(indent) = c {
+                *indent
+            } else {
+                0
+            }
+        })
+        .sum();
+
+    if leading_spaces > list_indentation {
+        span_lint_and_then(
+            cx,
+            DOC_OVERINDENTED_LIST_ITEM,
+            span,
+            "doc list item overindented",
+            |diag| {
+                diag.span_suggestion_verbose(
+                    span,
+                    "indent this line",
+                    std::iter::repeat(" ").take(list_indentation).join(""),
+                    Applicability::MaybeIncorrect,
+                );
+                diag.help("if this is supposed to be its own paragraph, add a blank line");
+            },
+        );
+    }
+}

tests/ui/doc/doc_lazy_list.fixed

@@ -1,4 +1,5 @@
 #![warn(clippy::doc_lazy_continuation)]
+#![allow(clippy::doc_overindented_list_item)]
 
 /// 1. nest here
 ///    lazy continuation

tests/ui/doc/doc_lazy_list.rs

@@ -1,4 +1,5 @@
 #![warn(clippy::doc_lazy_continuation)]
+#![allow(clippy::doc_overindented_list_item)]
 
 /// 1. nest here
 /// lazy continuation

tests/ui/doc/doc_lazy_list.stderr

@@ -1,5 +1,5 @@
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:4:5
+  --> tests/ui/doc/doc_lazy_list.rs:5:5
    |
 LL | /// lazy continuation
    |     ^
@@ -13,7 +13,7 @@ LL | ///    lazy continuation
    |     +++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:9:5
+  --> tests/ui/doc/doc_lazy_list.rs:10:5
    |
 LL | /// lazy list continuations don't make warnings with this lint
    |     ^
@@ -25,7 +25,7 @@ LL | ///    lazy list continuations don't make warnings with this lint
    |     +++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:11:5
+  --> tests/ui/doc/doc_lazy_list.rs:12:5
    |
 LL | /// because they don't have the
    |     ^
@@ -37,7 +37,7 @@ LL | ///    because they don't have the
    |     +++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:16:5
+  --> tests/ui/doc/doc_lazy_list.rs:17:5
    |
 LL | /// lazy continuation
    |     ^
@@ -49,7 +49,7 @@ LL | ///     lazy continuation
    |     ++++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:21:5
+  --> tests/ui/doc/doc_lazy_list.rs:22:5
    |
 LL | /// lazy list continuations don't make warnings with this lint
    |     ^
@@ -61,7 +61,7 @@ LL | ///     lazy list continuations don't make warnings with this lint
    |     ++++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:23:5
+  --> tests/ui/doc/doc_lazy_list.rs:24:5
    |
 LL | /// because they don't have the
    |     ^
@@ -73,7 +73,7 @@ LL | ///     because they don't have the
    |     ++++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:28:5
+  --> tests/ui/doc/doc_lazy_list.rs:29:5
    |
 LL | /// lazy continuation
    |     ^
@@ -85,7 +85,7 @@ LL | ///     lazy continuation
    |     ++++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:33:5
+  --> tests/ui/doc/doc_lazy_list.rs:34:5
    |
 LL | /// this will warn on the lazy continuation
    |     ^
@@ -97,7 +97,7 @@ LL | ///       this will warn on the lazy continuation
    |     ++++++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:35:5
+  --> tests/ui/doc/doc_lazy_list.rs:36:5
    |
 LL | ///     and so should this
    |     ^^^^
@@ -109,7 +109,7 @@ LL | ///       and so should this
    |         ++
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:56:5
+  --> tests/ui/doc/doc_lazy_list.rs:57:5
    |
 LL | ///  'protocol_descriptors': [
    |     ^
@@ -121,7 +121,7 @@ LL | ///   'protocol_descriptors': [
    |      +
 
 error: doc list item without indentation
-  --> tests/ui/doc/doc_lazy_list.rs:75:5
+  --> tests/ui/doc/doc_lazy_list.rs:76:5
    |
 LL | ///  ]
    |     ^

tests/ui/doc/doc_overindented_list_item.fixed

@@ -0,0 +1,28 @@
+#![warn(clippy::doc_overindented_list_item)]
+
+#[rustfmt::skip]
+/// - first list item
+///   overindented line
+//~^ ERROR: doc list item overindented
+///   this is overindented line too
+//~^ ERROR: doc list item overindented
+/// - second list item
+fn foo() {}
+
+#[rustfmt::skip]
+///   - first list item
+///     overindented line
+//~^ ERROR: doc list item overindented
+///     this is overindented line too
+//~^ ERROR: doc list item overindented
+///   - second list item
+fn bar() {}
+
+#[rustfmt::skip]
+/// * first list item
+///   overindented line
+//~^ ERROR: doc list item overindented
+///   this is overindented line too
+//~^ ERROR: doc list item overindented
+/// * second list item
+fn baz() {}

tests/ui/doc/doc_overindented_list_item.rs

@@ -0,0 +1,28 @@
+#![warn(clippy::doc_overindented_list_item)]
+
+#[rustfmt::skip]
+/// - first list item
+///        overindented line
+//~^ ERROR: doc list item overindented
+///      this is overindented line too
+//~^ ERROR: doc list item overindented
+/// - second list item
+fn foo() {}
+
+#[rustfmt::skip]
+///   - first list item
+///        overindented line
+//~^ ERROR: doc list item overindented
+///      this is overindented line too
+//~^ ERROR: doc list item overindented
+///   - second list item
+fn bar() {}
+
+#[rustfmt::skip]
+/// * first list item
+///        overindented line
+//~^ ERROR: doc list item overindented
+///      this is overindented line too
+//~^ ERROR: doc list item overindented
+/// * second list item
+fn baz() {}