Add tests for escape-sequence-in-docstring (#5362)

## Summary

Looks like I added a regression in #5360. This PR fixes it and adds
dedicated tests to avoid it in the future.

crates/ruff/resources/test/fixtures/pydocstyle/D301.py

@@ -0,0 +1,29 @@
+def double_quotes_backslash():
+    """Sum\\mary."""
+
+
+def double_quotes_backslash_raw():
+    r"""Sum\mary."""
+
+
+def double_quotes_backslash_uppercase():
+    R"""Sum\\mary."""
+
+
+def make_unique_pod_id(pod_id: str) -> str | None:
+    r"""
+    Generate a unique Pod name.
+
+    Kubernetes pod names must consist of one or more lowercase
+    rfc1035/rfc1123 labels separated by '.' with a maximum length of 253
+    characters.
+
+    Name must pass the following regex for validation
+    ``^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$``
+
+    For more details, see:
+    https://github.com/kubernetes/kubernetes/blob/release-1.1/docs/design/identifiers.md
+
+    :param pod_id: requested pod name
+    :return: ``str`` valid Pod name of appropriate length
+    """

crates/ruff/src/rules/pydocstyle/mod.rs

@@ -82,6 +82,7 @@ mod tests {
     #[test_case(Rule::SectionUnderlineNotOverIndented, Path::new("sections.py"))]
     #[test_case(Rule::OverloadWithDocstring, Path::new("D.py"))]
     #[test_case(Rule::EscapeSequenceInDocstring, Path::new("D.py"))]
+    #[test_case(Rule::EscapeSequenceInDocstring, Path::new("D301.py"))]
     #[test_case(Rule::TripleSingleQuotes, Path::new("D.py"))]
     fn rules(rule_code: Rule, path: &Path) -> Result<()> {
         let snapshot = format!("{}_{}", rule_code.noqa_code(), path.to_string_lossy());

crates/ruff/src/rules/pydocstyle/rules/backslashes.rs

@@ -54,14 +54,14 @@ impl Violation for EscapeSequenceInDocstring {
 
 /// D301
 pub(crate) fn backslashes(checker: &mut Checker, docstring: &Docstring) {
-    let body = docstring.body();
-
     // Docstring is already raw.
-    if body.starts_with('r') || body.starts_with("ur") {
+    let contents = docstring.contents;
+    if contents.starts_with('r') || contents.starts_with("ur") {
         return;
     }
 
     // Docstring contains at least one backslash.
+    let body = docstring.body();
     let bytes = body.as_bytes();
     if memchr_iter(b'\\', bytes).any(|position| {
         let escaped_char = bytes.get(position.saturating_add(1));

crates/ruff/src/rules/pydocstyle/snapshots/ruff__rules__pydocstyle__tests__D301_D301.py.snap

@@ -0,0 +1,18 @@
+---
+source: crates/ruff/src/rules/pydocstyle/mod.rs
+---
+D301.py:2:5: D301 Use `r"""` if any backslashes in a docstring
+  |
+1 | def double_quotes_backslash():
+2 |     """Sum\\mary."""
+  |     ^^^^^^^^^^^^^^^^ D301
+  |
+
+D301.py:10:5: D301 Use `r"""` if any backslashes in a docstring
+   |
+ 9 | def double_quotes_backslash_uppercase():
+10 |     R"""Sum\\mary."""
+   |     ^^^^^^^^^^^^^^^^^ D301
+   |
+
+