Fix panic in fuzzy-select when using non-ASCII characters

[stormshield-kg]

Fixes #181.

Use the str::char_indices() to keep valid byte offsets in memory.

Also add handling of the Delete key.

[Gordon01]

I tested this PR and it indeed fixes the problem with non-ASCII characters.

However, I believe that format_fuzzy_select_prompt() may be the only one that needs to be fixed to correctly support UTF-8.
Specifically replace indexing with .chars() method as described here: https://stackoverflow.com/questions/48642342/how-to-get-the-last-character-of-a-str

[Gordon01]

Thanks for this PR

[Gordon01]

I believe we don't need an optimization for search_term indexes.
It's small (will fit into the L1 cache) so recalculating it in a loop will not affect performance much.

Details

diff --git a/src/prompts/fuzzy_select.rs b/src/prompts/fuzzy_select.rs
index 39824be..3f83947 100644
--- a/src/prompts/fuzzy_select.rs
+++ b/src/prompts/fuzzy_select.rs
@@ -195,18 +195,9 @@ impl FuzzySelect<'_> {
 
     fn _interact_on(self, term: &Term, allow_quit: bool) -> Result<Option<usize>> {
         // Place cursor at the end of the search term
-        let mut bytes_position = self.initial_text.len();
+        let mut cursor = self.initial_text.chars().count();
         let mut search_term = self.initial_text.to_owned();
 
-        let mut position_indices = search_term
-            .char_indices()
-            .map(|(index, _)| index)
-            .collect::<Vec<_>>();
-
-        position_indices.push(search_term.len());
-
-        let mut char_index = position_indices.len() - 1;
-
         let mut render = TermThemeRenderer::new(term, self.theme);
         let mut sel = self.default;
 
@@ -233,8 +224,14 @@ impl FuzzySelect<'_> {
         let mut vim_mode = false;
 
         loop {
+            let mut byte_indices = search_term
+                .char_indices()
+                .map(|(index, _)| index)
+                .collect::<Vec<_>>();
+            byte_indices.push(search_term.len());
+
             render.clear()?;
-            render.fuzzy_select_prompt(self.prompt.as_str(), &search_term, bytes_position)?;
+            render.fuzzy_select_prompt(self.prompt.as_str(), &search_term, byte_indices[cursor])?;
 
             // Maps all items to a tuple of item and its match score.
             let mut filtered_list = self
@@ -313,16 +310,14 @@ impl FuzzySelect<'_> {
                     }
                     term.flush()?;
                 }
-                (Key::ArrowLeft, _, _) | (Key::Char('h'), _, true) if char_index > 0 => {
-                    char_index -= 1;
-                    bytes_position = position_indices[char_index];
+                (Key::ArrowLeft, _, _) | (Key::Char('h'), _, true) if cursor > 0 => {
+                    cursor -= 1;
                     term.flush()?;
                 }
                 (Key::ArrowRight, _, _) | (Key::Char('l'), _, true)
-                    if char_index < position_indices.len() - 1 =>
+                    if cursor < byte_indices.len() - 1 =>
                 {
-                    char_index += 1;
-                    bytes_position = position_indices[char_index];
+                    cursor += 1;
                     term.flush()?;
                 }
                 (Key::Enter, Some(sel), _) if !filtered_list.is_empty() => {
@@ -342,44 +337,18 @@ impl FuzzySelect<'_> {
                     term.show_cursor()?;
                     return Ok(sel_string_pos_in_items);
                 }
-                (Key::Backspace, _, _) if char_index > 0 => {
-                    let old_position = bytes_position;
-
-                    char_index -= 1;
-                    bytes_position = position_indices[char_index];
-
-                    let char_len = old_position - bytes_position;
-                    position_indices.remove(char_index);
-                    for index in &mut position_indices[char_index..] {
-                        *index -= char_len;
-                    }
-
-                    search_term.replace_range(bytes_position..old_position, "");
+                (Key::Backspace, _, _) if cursor > 0 => {
+                    cursor -= 1;
+                    search_term.remove(byte_indices[cursor]);
                     term.flush()?;
                 }
-                (Key::Del, _, _) if char_index < position_indices.len() - 1 => {
-                    let char_len = position_indices[char_index + 1] - bytes_position;
-                    position_indices.remove(char_index + 1);
-
-                    for index in &mut position_indices[char_index + 1..] {
-                        *index -= char_len;
-                    }
-
-                    search_term.replace_range(bytes_position..bytes_position + char_len, "");
+                (Key::Del, _, _) if cursor < byte_indices.len() - 1 => {
+                    search_term.remove(byte_indices[cursor]);
                     term.flush()?;
                 }
                 (Key::Char(chr), _, _) if !chr.is_ascii_control() => {
-                    let char_len = chr.len_utf8();
-                    let old_position = bytes_position;
-                    bytes_position += char_len;
-                    position_indices.insert(char_index, old_position);
-
-                    char_index += 1;
-                    for index in &mut position_indices[char_index..] {
-                        *index += char_len;
-                    }
-
-                    search_term.insert(old_position, chr);
+                    search_term.insert(byte_indices[cursor], chr);
+                    cursor += 1;
                     term.flush()?;
                     sel = Some(0);
                     starting_row = 0;

[Gordon01]

Please consider the attached diff.

Also, please update the changelog.

[Gordon01]

Just realized that Input builds a Vec of chars. That's also a way for code simplification. https://github.com/console-rs/dialoguer/blob/master/src/prompts/input.rs#L321

[Gordon01]

Let's add Delete key handling to Input too, since it also lacks this functionality.

[Gordon01]

Looks great, thank you!

@pksunkara please allow CI to run

[Gordon01]

LGTM