preserve trailing slash on Windows

src/lib.rs

@@ -65,6 +65,33 @@ use std::borrow::Cow;
 use std::ffi::OsStr;
 use std::path::{Path, PathBuf, MAIN_SEPARATOR};
 
+#[cfg(target_os = "windows")]
+mod windows {
+    use super::*;
+    use std::io::{self, Write};
+
+    #[derive(Default)]
+    struct EndsWithMainSep(bool);
+
+    impl io::Write for EndsWithMainSep {
+        fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+            self.0 = buf.ends_with(&[MAIN_SEPARATOR as u8]);
+            Ok(buf.len())
+        }
+        fn flush(&mut self) -> io::Result<()> {
+            Ok(())
+        }
+    }
+
+    // Workaround for Windows. There is no way to extract raw byte sequence from `OsStr` (in `Path`).
+    // And `OsStr::to_string_lossy` may cause extra heap allocation.
+    pub fn ends_with_main_sep(p: &Path) -> bool {
+        let mut w = EndsWithMainSep::default();
+        write!(&mut w, "{}", p.display()).unwrap();
+        w.0
+    }
+}
+
 fn str_to_path(s: &str, sep: char) -> Cow<'_, Path> {
     let mut buf = String::new();
 
@@ -155,7 +182,7 @@ impl PathExt for Path {
             buf.push('/');
         }
 
-        if buf != "/" && buf.ends_with('/') {
+        if !windows::ends_with_main_sep(self) && buf != "/" && buf.ends_with('/') {
             buf.pop(); // Pop last '/'
         }
 
@@ -204,7 +231,7 @@ impl PathExt for Path {
             buf.push('/');
         }
 
-        if buf != "/" && buf.ends_with('/') {
+        if !windows::ends_with_main_sep(self) && buf != "/" && buf.ends_with('/') {
             buf.pop(); // Pop last '/'
         }
 

src/test.rs

@@ -13,8 +13,8 @@ lazy_static! {
             ("//", "/"),
             ("foo", "foo"),
             ("/foo", "/foo"),
-            ("foo/", "foo"),
-            ("/foo/", "/foo"),
+            ("foo/", "foo/"),
+            ("/foo/", "/foo/"),
             ("./foo", "./foo"),
             ("../foo", "../foo"),
             ("foo/.", "foo/."),
@@ -116,8 +116,8 @@ lazy_static! {
             "/",
             "foo",
             "/foo",
-            "foo",
-            "/foo",
+            "foo/",
+            "/foo/",
             "./foo",
             "../foo",
             "foo/..",