From 98209be8aa8f3fe20a8f3e97d2d8ffcc9bc6c3be Mon Sep 17 00:00:00 2001
From: Martin Packman <gzlist@googlemail.com>
Date: Fri, 3 Mar 2023 04:59:33 +0000
Subject: [PATCH] Detect quote style ignoring docstrings (#3306)

Currently the quote style of the first string in a file is used for autodetecting what to use when rewriting code for fixes. This is an okay heuristic, but often the first line in a file is a docstring, rather than a string constant, and it's not uncommon for pre-Black code to have different quoting styles for those.

For example, in the Google style guide:
https://google.github.io/styleguide/pyguide.html
> Be consistent with your choice of string quote character within a file. Pick ' or " and stick with it. ... Docstrings must use """ regardless.

This branch adjusts the logic to instead skip over any `"""` triple doublequote string tokens. The default, if there are no single quoted strings, is still to use double quote as the style.
---
 crates/ruff/src/source_code/stylist.rs | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/crates/ruff/src/source_code/stylist.rs b/crates/ruff/src/source_code/stylist.rs
index 8b4c726566..8bcf141be4 100644
--- a/crates/ruff/src/source_code/stylist.rs
+++ b/crates/ruff/src/source_code/stylist.rs
@@ -180,7 +180,9 @@ fn detect_quote(contents: &str, locator: &Locator) -> Option<Quote> {
         if let Tok::String { .. } = tok {
             let content = locator.slice(&Range::new(start, end));
             if let Some(pattern) = leading_quote(content) {
-                if pattern.contains('\'') {
+                if pattern.contains("\"\"\"") {
+                    continue;
+                } else if pattern.contains('\'') {
                     return Some(Quote::Single);
                 } else if pattern.contains('"') {
                     return Some(Quote::Double);
@@ -276,13 +278,27 @@ x = (
         let locator = Locator::new(contents);
         assert_eq!(detect_quote(contents, &locator), Some(Quote::Double));
 
+        let contents = r#"s = "It's done.""#;
+        let locator = Locator::new(contents);
+        assert_eq!(detect_quote(contents, &locator), Some(Quote::Double));
+
+        // No style if only double quoted docstring (will take default Double)
         let contents = r#"
 def f():
     """Docstring."""
     pass
 "#;
         let locator = Locator::new(contents);
-        assert_eq!(detect_quote(contents, &locator), Some(Quote::Double));
+        assert_eq!(detect_quote(contents, &locator), None);
+
+        // Detect from string literal appearing after docstring
+        let contents = r#"
+"""Module docstring."""
+
+a = 'v'
+"#;
+        let locator = Locator::new(contents);
+        assert_eq!(detect_quote(contents, &locator), Some(Quote::Single));
     }
 
     #[test]