Ignore single quote docstrings with newline escape

**Summary** Ignore the edge case whether a single quoted string is multiple lines through an
escape, previously emitting invalid code. Single quote docstrings are
flagged by D300.
```python
"\
"
```

Fixes #7139

**Test Plan** New `D` fixture.

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

@@ -639,3 +639,8 @@ def starts_with_space_then_this():
 class SameLine: """This is a docstring on the same line"""
 
 def same_line(): """This is a docstring on the same line"""
+
+
+def single_line_docstring_with_an_escaped_backslash():
+    "\
+    "

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

@@ -90,13 +90,21 @@ pub(crate) fn ends_with_period(checker: &mut Checker, docstring: &Docstring) {
         let line = lines.nth(index).unwrap();
         let trimmed = line.trim_end();
 
+        if trimmed.ends_with("\\") {
+            // Ignore the edge case whether a single quoted string is multiple lines through an
+            // escape (https://github.com/astral-sh/ruff/issues/7139). Single quote docstrings are
+            // flagged by D300.
+            // ```python
+            // "\
+            // "
+            // ```
+            return;
+        }
+
         if !trimmed.ends_with('.') {
             let mut diagnostic = Diagnostic::new(EndsInPeriod, docstring.range());
             // Best-effort autofix: avoid adding a period after other punctuation marks.
-            if checker.patch(diagnostic.kind.rule())
-                && !trimmed.ends_with(':')
-                && !trimmed.ends_with(';')
-            {
+            if checker.patch(diagnostic.kind.rule()) && !trimmed.ends_with([':', ';']) {
                 diagnostic.set_fix(Fix::suggested(Edit::insertion(
                     ".".to_string(),
                     line.start() + trimmed.text_len(),

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

@@ -89,6 +89,17 @@ pub(crate) fn ends_with_punctuation(checker: &mut Checker, docstring: &Docstring
         let line = lines.next().unwrap();
         let trimmed = line.trim_end();
 
+        if trimmed.ends_with("\\") {
+            // Ignore the edge case whether a single quoted string is multiple lines through an
+            // escape (https://github.com/astral-sh/ruff/issues/7139). Single quote docstrings are
+            // flagged by D300.
+            // ```python
+            // "\
+            // "
+            // ```
+            return;
+        }
+
         if !trimmed.ends_with(['.', '!', '?']) {
             let mut diagnostic = Diagnostic::new(EndsInPunctuation, docstring.range());
             // Best-effort autofix: avoid adding a period after other punctuation marks.

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

@@ -151,6 +151,15 @@ pub(crate) fn multi_line_summary_start(checker: &mut Checker, docstring: &Docstr
             }
             checker.diagnostics.push(diagnostic);
         }
+    } else if first_line.as_str().ends_with("\\") {
+        // Ignore the edge case whether a single quoted string is multiple lines through an
+        // escape (https://github.com/astral-sh/ruff/issues/7139). Single quote docstrings are
+        // flagged by D300.
+        // ```python
+        // "\
+        // "
+        // ```
+        return;
     } else {
         if checker.enabled(Rule::MultiLineSummarySecondLine) {
             let mut diagnostic = Diagnostic::new(MultiLineSummarySecondLine, docstring.range());

crates/ruff/src/rules/pydocstyle/snapshots/ruff__rules__pydocstyle__tests__D200_D.py.snap

@@ -97,4 +97,14 @@ D.py:624:5: D200 One-line docstring should fit on one line
     |
     = help: Reformat to one line
 
+D.py:645:5: D200 One-line docstring should fit on one line
+    |
+644 |   def single_line_docstring_with_an_escaped_backslash():
+645 |       "\
+    |  _____^
+646 | |     "
+    | |_____^ D200
+    |
+    = help: Reformat to one line
+
 

crates/ruff/src/rules/pydocstyle/snapshots/ruff__rules__pydocstyle__tests__D300_D.py.snap

@@ -41,4 +41,13 @@ D.py:328:5: D300 Use triple double quotes `"""`
     |     ^^^^^^^^^^^^ D300
     |
 
+D.py:645:5: D300 Use triple double quotes `"""`
+    |
+644 |   def single_line_docstring_with_an_escaped_backslash():
+645 |       "\
+    |  _____^
+646 | |     "
+    | |_____^ D300
+    |
+
 

crates/ruff/src/rules/pydocstyle/snapshots/ruff__rules__pydocstyle__tests__D400_D.py.snap

@@ -289,6 +289,7 @@ D.py:639:17: D400 [*] First line should end with a period
     639 |+class SameLine: """This is a docstring on the same line."""
 640 640 | 
 641 641 | def same_line(): """This is a docstring on the same line"""
+642 642 | 
 
 D.py:641:18: D400 [*] First line should end with a period
     |
@@ -305,5 +306,8 @@ D.py:641:18: D400 [*] First line should end with a period
 640 640 | 
 641     |-def same_line(): """This is a docstring on the same line"""
     641 |+def same_line(): """This is a docstring on the same line."""
+642 642 | 
+643 643 | 
+644 644 | def single_line_docstring_with_an_escaped_backslash():
 
 

crates/ruff/src/rules/pydocstyle/snapshots/ruff__rules__pydocstyle__tests__D415_D.py.snap

@@ -271,6 +271,7 @@ D.py:639:17: D415 [*] First line should end with a period, question mark, or exc
     639 |+class SameLine: """This is a docstring on the same line."""
 640 640 | 
 641 641 | def same_line(): """This is a docstring on the same line"""
+642 642 | 
 
 D.py:641:18: D415 [*] First line should end with a period, question mark, or exclamation point
     |
@@ -287,5 +288,8 @@ D.py:641:18: D415 [*] First line should end with a period, question mark, or exc
 640 640 | 
 641     |-def same_line(): """This is a docstring on the same line"""
     641 |+def same_line(): """This is a docstring on the same line."""
+642 642 | 
+643 643 | 
+644 644 | def single_line_docstring_with_an_escaped_backslash():