Keep a forward slash when autocomplete on Windows

When autocomplete path with `/` on Windows, paths remains with slash
instead of backslash(`\`).

If mixed both, path completion uses a last path seperator.

crates/nu-cli/src/completions/completion_common.rs

@@ -10,9 +10,7 @@ use nu_protocol::{
     levenshtein_distance, Span,
 };
 use nu_utils::get_ls_colors;
-use std::path::{
-    is_separator, Component, Path, PathBuf, MAIN_SEPARATOR as SEP, MAIN_SEPARATOR_STR,
-};
+use std::path::{is_separator, Component, Path, PathBuf, MAIN_SEPARATOR as SEP};
 
 use super::SortBy;
 
@@ -93,16 +91,16 @@ enum OriginalCwd {
 }
 
 impl OriginalCwd {
-    fn apply(&self, mut p: PathBuiltFromString) -> String {
+    fn apply(&self, mut p: PathBuiltFromString, path_separator: char) -> String {
         match self {
             Self::None => {}
             Self::Home => p.parts.insert(0, "~".to_string()),
             Self::Prefix(s) => p.parts.insert(0, s.clone()),
         };
 
-        let mut ret = p.parts.join(MAIN_SEPARATOR_STR);
+        let mut ret = p.parts.join(&path_separator.to_string());
         if p.isdir {
-            ret.push(SEP);
+            ret.push(path_separator);
         }
         ret
     }
@@ -133,6 +131,14 @@ pub fn complete_item(
 ) -> Vec<(nu_protocol::Span, String, Option<Style>)> {
     let partial = surround_remove(partial);
     let isdir = partial.ends_with(is_separator);
+
+    #[cfg(unix)]
+    let path_separator = SEP;
+    #[cfg(windows)]
+    let path_separator = partial
+        .chars()
+        .rfind(|c: &char| is_separator(*c))
+        .unwrap_or(SEP);
     let cwd_pathbuf = Path::new(cwd).to_path_buf();
     let ls_colors = (engine_state.config.use_ls_colors_completions
         && engine_state.config.use_ansi_coloring)
@@ -195,7 +201,7 @@ pub fn complete_item(
     )
     .into_iter()
     .map(|p| {
-        let path = original_cwd.apply(p);
+        let path = original_cwd.apply(p, path_separator);
         let style = ls_colors.as_ref().map(|lsc| {
             lsc.style_for_path_with_metadata(
                 &path,

crates/nu-cli/tests/completions/mod.rs

@@ -32,7 +32,6 @@ fn completer() -> NuCompleter {
 fn completer_strings() -> NuCompleter {
     // Create a new engine
     let (dir, _, mut engine, mut stack) = new_engine();
-
     // Add record value as example
     let record = r#"def animals [] { ["cat", "dog", "eel" ] }
     def my-command [animal: string@animals] { print $animal }"#;
@@ -258,6 +257,20 @@ fn file_completions() {
         folder(dir.join(".hidden_folder")),
     ];
 
+    #[cfg(windows)]
+    {
+        let separator = '/';
+        let target_dir = format!("cp {dir_str}{separator}");
+        let slash_suggestions = completer.complete(&target_dir, target_dir.len());
+
+        let expected_slash_paths = expected_paths
+            .iter()
+            .map(|s| s.replace('\\', "/"))
+            .collect();
+
+        match_suggestions(expected_slash_paths, slash_suggestions);
+    }
+
     // Match the results
     match_suggestions(expected_paths, suggestions);
 
@@ -272,12 +285,25 @@ fn file_completions() {
     match_suggestions(expected_paths, suggestions);
 
     // Test completions for hidden files
-    let target_dir = format!("ls {}/.", folder(dir.join(".hidden_folder")));
+    let target_dir = format!("ls {}{MAIN_SEPARATOR}.", folder(dir.join(".hidden_folder")));
     let suggestions = completer.complete(&target_dir, target_dir.len());
 
     let expected_paths: Vec<String> =
         vec![file(dir.join(".hidden_folder").join(".hidden_subfile"))];
 
+    #[cfg(windows)]
+    {
+        let target_dir = format!("ls {}/.", folder(dir.join(".hidden_folder")));
+        let slash_suggestions = completer.complete(&target_dir, target_dir.len());
+
+        let expected_slash = expected_paths
+            .iter()
+            .map(|s| s.replace('\\', "/"))
+            .collect();
+
+        match_suggestions(expected_slash, slash_suggestions)
+    }
+
     // Match the results
     match_suggestions(expected_paths, suggestions);
 }
@@ -464,6 +490,7 @@ fn command_ls_with_filecompletion() {
 
     match_suggestions(expected_paths, suggestions)
 }
+
 #[test]
 fn command_open_with_filecompletion() {
     let (_, _, engine, stack) = new_engine();
@@ -794,6 +821,19 @@ fn folder_with_directorycompletions() {
         folder(dir.join(".hidden_folder")),
     ];
 
+    #[cfg(windows)]
+    {
+        let target_dir = format!("cd {dir_str}/");
+        let slash_suggestions = completer.complete(&target_dir, target_dir.len());
+
+        let expected_slash_paths = expected_paths
+            .iter()
+            .map(|s| s.replace('\\', "/"))
+            .collect();
+
+        match_suggestions(expected_slash_paths, slash_suggestions);
+    }
+
     // Match the results
     match_suggestions(expected_paths, suggestions);
 }