Make sure we don't remove a windows drive slash when shortening a path.

Author: o0Ignition0o

src/parser.rs

@@ -1230,13 +1230,12 @@ impl<'a> Parser<'a> {
                 | ".%2E" => {
                     debug_assert!(self.serialization.as_bytes()[segment_start - 1] == b'/');
                     self.serialization.truncate(segment_start);
-                    // Do not remove the root slash
-                    if self.serialization.ends_with("/") && path_start + 1 < segment_start {
+                    if self.serialization.ends_with("/")
+                        && Parser::last_slash_can_be_removed(&self.serialization, path_start)
+                    {
                         self.serialization.pop();
-                        self.shorten_path(scheme_type, path_start);
-                    } else {
-                        self.shorten_path(scheme_type, path_start);
                     }
+                    self.shorten_path(scheme_type, path_start);
 
                     // and then if neither c is U+002F (/), nor url is special and c is U+005C (\), append the empty string to url’s path.
                     if ends_with_slash && !self.serialization.ends_with("/") {
@@ -1281,6 +1280,18 @@ impl<'a> Parser<'a> {
         input
     }
 
+    fn last_slash_can_be_removed(serialization: &String, path_start: usize) -> bool {
+        let url_before_segment = &serialization[..serialization.len() - 1];
+        if let Some(segment_before_start) = url_before_segment.rfind("/") {
+            // Do not remove the root slash
+            segment_before_start >= path_start
+                // Or a windows drive letter slash
+                && !path_starts_with_windows_drive_letter(&serialization[segment_before_start..])
+        } else {
+            false
+        }
+    }
+
     /// https://url.spec.whatwg.org/#shorten-a-urls-path
     fn shorten_path(&mut self, scheme_type: SchemeType, path_start: usize) {
         // If path is empty, then return.
@@ -1553,8 +1564,18 @@ fn is_windows_drive_letter(segment: &str) -> bool {
     segment.len() == 2 && starts_with_windows_drive_letter(segment)
 }
 
+/// Wether path starts with a root slash
+/// and a windows drive letter eg: "/c:" or "/a:/"
+fn path_starts_with_windows_drive_letter(s: &str) -> bool {
+    s.len() > 3
+        && matches!(s.as_bytes()[0], b'/' | b'\\' | b'?' | b'#')
+        && starts_with_windows_drive_letter(&s[1..])
+}
+
 fn starts_with_windows_drive_letter(s: &str) -> bool {
-    ascii_alpha(s.as_bytes()[0] as char) && matches!(s.as_bytes()[1], b':' | b'|')
+    ascii_alpha(s.as_bytes()[0] as char)
+        && matches!(s.as_bytes()[1], b':' | b'|')
+        && (s.len() == 2 || matches!(s.as_bytes()[2], b'/' | b'\\' | b'?' | b'#'))
 }
 
 /// https://url.spec.whatwg.org/#start-with-a-windows-drive-letter