Add autofix for F504 and F522 (#1184)

src/python/string.rs

@@ -1,3 +1,9 @@
+use once_cell::sync::Lazy;
+use regex::Regex;
+
+pub static STRING_QUOTE_PREFIX_REGEX: Lazy<Regex> =
+    Lazy::new(|| Regex::new(r#"^(?i)[urb]*['"](?P<raw>.*)['"]$"#).unwrap());
+
 pub fn is_lower(s: &str) -> bool {
     let mut cased = false;
     for c in s.chars() {
@@ -22,9 +28,22 @@ pub fn is_upper(s: &str) -> bool {
     cased
 }
 
+/// Remove prefixes (u, r, b) and quotes around a string. This expects the given
+/// string to be a valid Python string representation, it doesn't do any
+/// validation.
+pub fn strip_quotes_and_prefixes(s: &str) -> &str {
+    match STRING_QUOTE_PREFIX_REGEX.captures(s) {
+        Some(caps) => match caps.name("raw") {
+            Some(m) => m.as_str(),
+            None => s,
+        },
+        None => s,
+    }
+}
+
 #[cfg(test)]
 mod tests {
-    use crate::python::string::{is_lower, is_upper};
+    use crate::python::string::{is_lower, is_upper, strip_quotes_and_prefixes};
 
     #[test]
     fn test_is_lower() {
@@ -47,4 +66,12 @@ mod tests {
         assert!(!is_upper(""));
         assert!(!is_upper("_"));
     }
+
+    #[test]
+    fn test_strip_quotes_and_prefixes() {
+        assert_eq!(strip_quotes_and_prefixes(r#"'a'"#), "a");
+        assert_eq!(strip_quotes_and_prefixes(r#"bur'a'"#), "a");
+        assert_eq!(strip_quotes_and_prefixes(r#"UrB'a'"#), "a");
+        assert_eq!(strip_quotes_and_prefixes(r#""a""#), "a");
+    }
 }