Don't slice line in DefaultCompleter (#695)

* Don't slice line in DefaultCompleter

* Revert completions example

* Fix clippy lint

* Treat input as '' if None

* Update values even if string_difference empty

* Rename start to pos in list_menu

* Fix string_diff bug with repeated char

* Trim before completing in DefaultCompleter

* Remove TODO

* Make HistoryCompleter take end as pos

src/completion/base.rs

@@ -24,7 +24,8 @@ impl Span {
     }
 }
 
-/// A trait that defines how to convert a line and position to a list of potential completions in that position.
+/// A trait that defines how to convert some text and a position to a list of potential completions in that position.
+/// The text could be a part of the whole line, and the position is the index of the end of the text in the original line.
 pub trait Completer: Send {
     /// the action that will take the line and position and convert it to a vector of completions, which include the
     /// span to replace and the contents of that replacement

src/completion/default.rs

@@ -71,8 +71,11 @@ impl Completer for DefaultCompleter {
     fn complete(&mut self, line: &str, pos: usize) -> Vec<Suggestion> {
         let mut span_line_whitespaces = 0;
         let mut completions = vec![];
+        // Trimming in case someone passes in text containing stuff after the cursor, if
+        // `only_buffer_difference` is false
+        let line = if line.len() > pos { &line[..pos] } else { line };
         if !line.is_empty() {
-            let mut split = line[0..pos].split(' ').rev();
+            let mut split = line.split(' ').rev();
             let mut span_line: String = String::new();
             for _ in 0..split.clone().count() {
                 if let Some(s) = split.next() {

src/completion/history.rs

@@ -52,8 +52,8 @@ impl<'menu> HistoryCompleter<'menu> {
 
     fn create_suggestion(&self, line: &str, pos: usize, value: &str) -> Suggestion {
         let span = Span {
-            start: pos,
-            end: pos + line.len(),
+            start: pos - line.len(),
+            end: pos,
         };
 
         Suggestion {

src/menu/columnar_menu.rs

@@ -526,13 +526,16 @@ impl Menu for ColumnarMenu {
 
     /// Updates menu values
     fn update_values(&mut self, editor: &mut Editor, completer: &mut dyn Completer) {
-        if self.only_buffer_difference {
+        self.values = if self.only_buffer_difference {
             if let Some(old_string) = &self.input {
                 let (start, input) = string_difference(editor.get_buffer(), old_string);
                 if !input.is_empty() {
-                    self.values = completer.complete(input, start);
-                    self.reset_position();
+                    completer.complete(input, start + input.len())
+                } else {
+                    completer.complete("", editor.insertion_point())
                 }
+            } else {
+                completer.complete("", editor.insertion_point())
             }
         } else {
             // If there is a new line character in the line buffer, the completer
@@ -541,9 +544,13 @@ impl Menu for ColumnarMenu {
             // Also, by replacing the new line character with a space, the insert
             // position is maintain in the line buffer.
             let trimmed_buffer = editor.get_buffer().replace('\n', " ");
-            self.values = completer.complete(trimmed_buffer.as_str(), editor.insertion_point());
-            self.reset_position();
-        }
+            completer.complete(
+                &trimmed_buffer[..editor.insertion_point()],
+                editor.insertion_point(),
+            )
+        };
+
+        self.reset_position();
     }
 
     /// The working details for the menu changes based on the size of the lines

src/menu/list_menu.rs

@@ -395,20 +395,23 @@ impl Menu for ListMenu {
     /// Collecting the value from the completer to be shown in the menu
     fn update_values(&mut self, editor: &mut Editor, completer: &mut dyn Completer) {
         let line_buffer = editor.line_buffer();
-        let (start, input) = if self.only_buffer_difference {
+        let (pos, input) = if self.only_buffer_difference {
             match &self.input {
                 Some(old_string) => {
                     let (start, input) = string_difference(line_buffer.get_buffer(), old_string);
                     if input.is_empty() {
                         (line_buffer.insertion_point(), "")
                     } else {
-                        (start, input)
+                        (start + input.len(), input)
                     }
                 }
                 None => (line_buffer.insertion_point(), ""),
             }
         } else {
-            (line_buffer.insertion_point(), line_buffer.get_buffer())
+            (
+                line_buffer.insertion_point(),
+                &line_buffer.get_buffer()[..line_buffer.insertion_point()],
+            )
         };
 
         let parsed = parse_selection_char(input, SELECTION_CHAR);
@@ -421,7 +424,7 @@ impl Menu for ListMenu {
         }
 
         self.values = if parsed.remainder.is_empty() {
-            self.query_size = Some(completer.total_completions(parsed.remainder, start));
+            self.query_size = Some(completer.total_completions(parsed.remainder, pos));
 
             let skip = self.pages.iter().take(self.page).sum::<Page>().size;
             let take = self
@@ -430,10 +433,10 @@ impl Menu for ListMenu {
                 .map(|page| page.size)
                 .unwrap_or(self.page_size);
 
-            completer.partial_complete(input, start, skip, take)
+            completer.partial_complete(input, pos, skip, take)
         } else {
             self.query_size = None;
-            completer.complete(input, start)
+            completer.complete(input, pos)
         }
     }
 

src/menu/menu_functions.rs

@@ -209,7 +209,7 @@ pub fn string_difference<'a>(new_string: &'a str, old_string: &str) -> (usize, &
                     false
                 }
             } else {
-                *c == old_chars[old_char_index].1
+                old_char_index == new_char_index && *c == old_chars[old_char_index].1
             };
 
             if equal {
@@ -479,6 +479,15 @@ mod tests {
         assert_eq!(res, (6, "ｓｈｅ"));
     }
 
+    #[test]
+    fn string_difference_with_repeat() {
+        let new_string = "ee";
+        let old_string = "e";
+
+        let res = string_difference(new_string, old_string);
+        assert_eq!(res, (1, "e"));
+    }
+
     #[test]
     fn find_common_string_with_ansi() {
         use crate::Span;