Make sure a windows drive letter segment always ends with a slash.

src/lib.rs

@@ -2508,6 +2508,7 @@ fn path_to_file_url_segments_windows(
     }
     let mut components = path.components();
 
+    let host_start = serialization.len() + 1;
     let host_end;
     let host_internal;
     match components.next() {
@@ -2534,15 +2535,24 @@ fn path_to_file_url_segments_windows(
         _ => return Err(()),
     }
 
+    let mut path_only_has_prefix = true;
     for component in components {
         if component == Component::RootDir {
             continue;
         }
+        path_only_has_prefix = false;
         // FIXME: somehow work with non-unicode?
         let component = component.as_os_str().to_str().ok_or(())?;
         serialization.push('/');
         serialization.extend(percent_encode(component.as_bytes(), PATH_SEGMENT));
     }
+    // A windows drive letter must end with a slash.
+    if serialization.len() > host_start
+        && parser::is_windows_drive_letter(&serialization[host_start..])
+        && path_only_has_prefix
+    {
+        serialization.push('/');
+    }
     Ok((host_end, host_internal))
 }
 
@@ -2567,6 +2577,14 @@ fn file_url_segments_to_pathbuf(
         bytes.push(b'/');
         bytes.extend(percent_decode(segment.as_bytes()));
     }
+    // A windows drive letter must end with a slash.
+    if bytes.len() > 2 {
+        if matches!(bytes[bytes.len() -2], b'a'..=b'z' | b'A'..=b'Z')
+            && matches!(bytes[bytes.len() - 1], b':' | b'|')
+        {
+            bytes.push(b'/');
+        }
+    }
     let os_str = OsStr::from_bytes(&bytes);
     let path = PathBuf::from(os_str);
     debug_assert!(

src/parser.rs

@@ -1571,7 +1571,8 @@ fn is_normalized_windows_drive_letter(segment: &str) -> bool {
 
 /// Wether the scheme is file:, the path has a single segment, and that segment
 /// is a Windows drive letter
-fn is_windows_drive_letter(segment: &str) -> bool {
+#[inline]
+pub fn is_windows_drive_letter(segment: &str) -> bool {
     segment.len() == 2 && starts_with_windows_drive_letter(segment)
 }
 

tests/unit.rs

@@ -564,3 +564,29 @@ fn test_options_reuse() {
     assert_eq!(url.as_str(), "http://mozilla.org/sub/path");
     assert_eq!(*violations.borrow(), vec!(ExpectedDoubleSlash, Backslash));
 }
+
+/// https://github.com/servo/rust-url/issues/505
+#[cfg(windows)]
+#[test]
+fn test_url_from_file_path() {
+    use std::path::PathBuf;
+    use url::Url;
+
+    let p = PathBuf::from("c:///");
+    let u = Url::from_file_path(p).unwrap();
+    let path = u.to_file_path().unwrap();
+    assert_eq!("C:\\", path.to_str().unwrap());
+}
+
+/// https://github.com/servo/rust-url/issues/505
+#[cfg(not(windows))]
+#[test]
+fn test_url_from_file_path() {
+    use std::path::PathBuf;
+    use url::Url;
+
+    let p = PathBuf::from("/c:/");
+    let u = Url::from_file_path(p).unwrap();
+    let path = u.to_file_path().unwrap();
+    assert_eq!("/c:/", path.to_str().unwrap());
+}