Fix menu::menu_functions::find_common_string (#363)

* Fix `menu::menu_functions::find_common_string`

* Add test for `DefaultCompleter`

* Add test strings

src/completion/default.rs

@@ -348,3 +348,40 @@ impl CompletionNode {
         completions
     }
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn default_completer_with_non_ansi() {
+        use super::*;
+
+        let mut completions = DefaultCompleter::default();
+        completions.insert(
+            vec!["ｎｕｓｈｅｌｌ", "ｎｕｌｌ", "ｎｕｍｂｅｒ"]
+                .iter()
+                .map(|s| s.to_string())
+                .collect(),
+        );
+
+        assert_eq!(
+            completions.complete("ｎ", 3),
+            vec![
+                Suggestion {
+                    value: "ｎｕｌｌ".into(),
+                    description: None,
+                    span: Span { start: 0, end: 3 },
+                },
+                Suggestion {
+                    value: "ｎｕｍｂｅｒ".into(),
+                    description: None,
+                    span: Span { start: 0, end: 3 },
+                },
+                Suggestion {
+                    value: "ｎｕｓｈｅｌｌ".into(),
+                    description: None,
+                    span: Span { start: 0, end: 3 },
+                },
+            ]
+        );
+    }
+}

src/main.rs

@@ -61,6 +61,8 @@ fn main() -> Result<()> {
         "abaaac".into(),
         "abaaaxyc".into(),
         "abaaarabc".into(),
+        "こんにちは世界".into(),
+        "こんばんは世界".into(),
     ];
 
     let completer = Box::new(DefaultCompleter::new_with_wordlen(commands.clone(), 2));

src/menu/menu_functions.rs

@@ -138,15 +138,15 @@ pub fn find_common_string(values: &[Suggestion]) -> (Option<&Suggestion>, Option
             } else {
                 first
                     .value
-                    .chars()
-                    .zip(suggestion.value.chars())
-                    .position(|(mut lhs, mut rhs)| {
+                    .char_indices()
+                    .zip(suggestion.value.char_indices())
+                    .find(|((_, mut lhs), (_, mut rhs))| {
                         lhs.make_ascii_lowercase();
                         rhs.make_ascii_lowercase();
 
                         lhs != rhs
                     })
-                    .map(|new_index| match index {
+                    .map(|((new_index, _), _)| match index {
                         Some(index) => {
                             if index <= new_index {
                                 index
@@ -403,4 +403,38 @@ mod tests {
         let res = string_difference(new_string, old_string);
         assert_eq!(res, (4, "b = ñ "));
     }
+
+    #[test]
+    fn find_common_string_with_ansi() {
+        use crate::Span;
+
+        let input: Vec<_> = ["nushell", "null"]
+            .into_iter()
+            .map(|s| Suggestion {
+                value: s.into(),
+                description: None,
+                span: Span::new(0, s.len()),
+            })
+            .collect();
+        let res = find_common_string(&input);
+
+        assert!(matches!(res, (Some(elem), Some(2)) if elem == &input[0]));
+    }
+
+    #[test]
+    fn find_common_string_with_non_ansi() {
+        use crate::Span;
+
+        let input: Vec<_> = ["ｎｕｓｈｅｌｌ", "ｎｕｌｌ"]
+            .into_iter()
+            .map(|s| Suggestion {
+                value: s.into(),
+                description: None,
+                span: Span::new(0, s.len()),
+            })
+            .collect();
+        let res = find_common_string(&input);
+
+        assert!(matches!(res, (Some(elem), Some(6)) if elem == &input[0]));
+    }
 }