Rollup merge of #101366 - ChrisDenton:unc-forward-slash, r=m-ou-se

Restore old behaviour on broken UNC paths

This fixes #101358 by restoring the behaviour from previous stable Rust versions. I'm not convinced this is ultimately right but I think it's less wrong and maybe this should be backported to beta?

r? libs

library/std/src/sys/windows/path.rs

@@ -198,14 +198,7 @@ fn parse_next_component(path: &OsStr, verbatim: bool) -> (&OsStr, &OsStr) {
 
     match path.bytes().iter().position(|&x| separator(x)) {
         Some(separator_start) => {
-            let mut separator_end = separator_start + 1;
-
-            // a series of multiple separator characters is treated as a single separator,
-            // except in verbatim paths
-            while !verbatim && separator_end < path.len() && separator(path.bytes()[separator_end])
-            {
-                separator_end += 1;
-            }
+            let separator_end = separator_start + 1;
 
             let component = &path.bytes()[..separator_start];
 

library/std/src/sys/windows/path/tests.rs

@@ -31,16 +31,6 @@ fn test_parse_next_component() {
         parse_next_component(OsStr::new(r"servershare"), false),
         (OsStr::new(r"servershare"), OsStr::new(""))
     );
-
-    assert_eq!(
-        parse_next_component(OsStr::new(r"server/\//\/\\\\/////\/share"), false),
-        (OsStr::new(r"server"), OsStr::new(r"share"))
-    );
-
-    assert_eq!(
-        parse_next_component(OsStr::new(r"server\\\\\\\\\\\\\\share"), true),
-        (OsStr::new(r"server"), OsStr::new(r"\\\\\\\\\\\\\share"))
-    );
 }
 
 #[test]
@@ -126,3 +116,22 @@ fn test_windows_prefix_components() {
     assert_eq!(drive.as_os_str(), OsStr::new("C:"));
     assert_eq!(components.as_path(), Path::new(""));
 }
+
+/// See #101358.
+///
+/// Note that the exact behaviour here may change in the future.
+/// In which case this test will need to adjusted.
+#[test]
+fn broken_unc_path() {
+    use crate::path::Component;
+
+    let mut components = Path::new(r"\\foo\\bar\\").components();
+    assert_eq!(components.next(), Some(Component::RootDir));
+    assert_eq!(components.next(), Some(Component::Normal("foo".as_ref())));
+    assert_eq!(components.next(), Some(Component::Normal("bar".as_ref())));
+
+    let mut components = Path::new("//foo//bar//").components();
+    assert_eq!(components.next(), Some(Component::RootDir));
+    assert_eq!(components.next(), Some(Component::Normal("foo".as_ref())));
+    assert_eq!(components.next(), Some(Component::Normal("bar".as_ref())));
+}