Enforce max-doc-length for multi-line docstrings (#4347)

crates/ruff/resources/test/fixtures/pycodestyle/W505.py

@@ -2,7 +2,7 @@
 """Here's a top-level docstring that's over the limit."""
 
 
-def f():
+def f1():
     """Here's a docstring that's also over the limit."""
 
     x = 1  # Here's a comment that's over the limit, but it's not standalone.
@@ -16,3 +16,16 @@ def f():
 
 
 "This is also considered a docstring, and is over the limit."
+
+
+def f2():
+    """Here's a multi-line docstring.
+
+    It's over the limit on this line, which isn't the first line in the docstring.
+    """
+
+
+def f3():
+    """Here's a multi-line docstring.
+
+    It's over the limit on this line, which isn't the first line in the docstring."""

crates/ruff/src/checkers/physical_lines.rs

@@ -118,7 +118,7 @@ pub fn check_physical_lines(
         }
 
         while doc_lines_iter
-            .next_if(|doc_line_start| line.range().contains(**doc_line_start))
+            .next_if(|doc_line_start| line.range().contains_inclusive(**doc_line_start))
             .is_some()
         {
             if enforce_doc_line_too_long {

crates/ruff/src/doc_lines.rs

@@ -1,14 +1,15 @@
 //! Doc line extraction. In this context, a doc line is a line consisting of a
 //! standalone comment or a constant string statement.
 
-use ruff_text_size::{TextRange, TextSize};
 use std::iter::FusedIterator;
 
-use ruff_python_ast::source_code::Locator;
+use ruff_text_size::{TextRange, TextSize};
 use rustpython_parser::ast::{Constant, ExprKind, Stmt, StmtKind, Suite};
 use rustpython_parser::lexer::LexResult;
 use rustpython_parser::Tok;
 
+use ruff_python_ast::newlines::UniversalNewlineIterator;
+use ruff_python_ast::source_code::Locator;
 use ruff_python_ast::visitor;
 use ruff_python_ast::visitor::Visitor;
 
@@ -69,29 +70,43 @@ impl Iterator for DocLines<'_> {
 
 impl FusedIterator for DocLines<'_> {}
 
-#[derive(Default)]
-struct StringLinesVisitor {
+struct StringLinesVisitor<'a> {
     string_lines: Vec<TextSize>,
+    locator: &'a Locator<'a>,
 }
 
-impl Visitor<'_> for StringLinesVisitor {
+impl Visitor<'_> for StringLinesVisitor<'_> {
     fn visit_stmt(&mut self, stmt: &Stmt) {
         if let StmtKind::Expr { value } = &stmt.node {
             if let ExprKind::Constant {
                 value: Constant::Str(..),
                 ..
             } = &value.node
             {
-                self.string_lines.push(value.start());
+                for line in UniversalNewlineIterator::with_offset(
+                    self.locator.slice(value.range()),
+                    value.start(),
+                ) {
+                    self.string_lines.push(line.start());
+                }
             }
         }
         visitor::walk_stmt(self, stmt);
     }
 }
 
+impl<'a> StringLinesVisitor<'a> {
+    fn new(locator: &'a Locator<'a>) -> Self {
+        Self {
+            string_lines: Vec::new(),
+            locator,
+        }
+    }
+}
+
 /// Extract doc lines (standalone strings) start positions from an AST.
-pub fn doc_lines_from_ast(python_ast: &Suite) -> Vec<TextSize> {
-    let mut visitor = StringLinesVisitor::default();
+pub fn doc_lines_from_ast(python_ast: &Suite, locator: &Locator) -> Vec<TextSize> {
+    let mut visitor = StringLinesVisitor::new(locator);
     visitor.visit_body(python_ast);
     visitor.string_lines
 }

crates/ruff/src/linter.rs

@@ -163,7 +163,7 @@ pub fn check_path(
                     diagnostics.extend(import_diagnostics);
                 }
                 if use_doc_lines {
-                    doc_lines.extend(doc_lines_from_ast(&python_ast));
+                    doc_lines.extend(doc_lines_from_ast(&python_ast, locator));
                 }
             }
             Err(parse_error) => {

crates/ruff/src/rules/pycodestyle/snapshots/ruff__rules__pycodestyle__tests__max_doc_length.snap

@@ -10,7 +10,7 @@ W505.py:2:51: W505 Doc line too long (57 > 50 characters)
 
 W505.py:6:51: W505 Doc line too long (56 > 50 characters)
   |
-6 | def f():
+6 | def f1():
 7 |     """Here's a docstring that's also over the limit."""
   |                                                   ^^^^^^ W505
 8 | 
@@ -42,4 +42,21 @@ W505.py:18:51: W505 Doc line too long (61 > 50 characters)
    |                                                   ^^^^^^^^^^^ W505
    |
 
+W505.py:24:51: W505 Doc line too long (82 > 50 characters)
+   |
+24 |     """Here's a multi-line docstring.
+25 | 
+26 |     It's over the limit on this line, which isn't the first line in the docstring.
+   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ W505
+27 |     """
+   |
+
+W505.py:31:51: W505 Doc line too long (85 > 50 characters)
+   |
+31 |     """Here's a multi-line docstring.
+32 | 
+33 |     It's over the limit on this line, which isn't the first line in the docstring."""
+   |                                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ W505
+   |
+