get back the ranges of the strings from the completer used for generating completions

src/completion/base.rs

@@ -1,3 +1,5 @@
+use std::ops::Range;
+
 /// A span of source code, with positions in bytes
 #[derive(Debug, Default, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash)]
 pub struct Span {
@@ -31,6 +33,22 @@ pub trait Completer: Send {
     /// span to replace and the contents of that replacement
     fn complete(&mut self, line: &str, pos: usize) -> Vec<Suggestion>;
 
+    /// same as [`Completer::complete`] but it will return a vector of ranges of the strings
+    /// the suggestions are based on
+    fn complete_with_base_ranges(
+        &mut self,
+        line: &str,
+        pos: usize,
+    ) -> (Vec<Suggestion>, Vec<Range<usize>>) {
+        let mut ranges = vec![];
+        let suggestions = self.complete(line, pos);
+        for suggestion in &suggestions {
+            ranges.push(suggestion.span.start..suggestion.span.end);
+        }
+        ranges.dedup();
+        (suggestions, ranges)
+    }
+
     /// action that will return a partial section of available completions
     /// this command comes handy when trying to avoid to pull all the data at once
     /// from the completer

src/completion/default.rs

@@ -356,10 +356,10 @@ impl CompletionNode {
 
 #[cfg(test)]
 mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
     #[test]
     fn default_completer_with_non_ansi() {
-        use super::*;
-
         let mut completions = DefaultCompleter::default();
         completions.insert(
             ["ｎｕｓｈｅｌｌ", "ｎｕｌｌ", "ｎｕｍｂｅｒ"]
@@ -395,4 +395,51 @@ mod tests {
             ]
         );
     }
+
+    #[test]
+    fn default_completer_with_start_strings() {
+        let mut completions = DefaultCompleter::default();
+        completions.insert(
+            ["this is the reedline crate", "test"]
+                .iter()
+                .map(|s| s.to_string())
+                .collect(),
+        );
+
+        let buffer = "this is t";
+
+        let (suggestions, ranges) = completions.complete_with_base_ranges(buffer, 9);
+        assert_eq!(
+            suggestions,
+            [
+                Suggestion {
+                    value: "test".into(),
+                    description: None,
+                    extra: None,
+                    span: Span { start: 8, end: 9 },
+                    append_whitespace: false,
+                },
+                Suggestion {
+                    value: "this is the reedline crate".into(),
+                    description: None,
+                    extra: None,
+                    span: Span { start: 8, end: 9 },
+                    append_whitespace: false,
+                },
+                Suggestion {
+                    value: "this is the reedline crate".into(),
+                    description: None,
+                    extra: None,
+                    span: Span { start: 0, end: 9 },
+                    append_whitespace: false,
+                },
+            ]
+        );
+
+        assert_eq!(ranges, [8..9, 0..9]);
+        assert_eq!(
+            ["t", "this is t"],
+            [&buffer[ranges[0].clone()], &buffer[ranges[1].clone()]]
+        );
+    }
 }

src/menu/columnar_menu.rs

@@ -728,10 +728,6 @@ impl Menu for ColumnarMenu {
                 .collect()
         }
     }
-
-    fn set_cursor_pos(&mut self, _pos: (u16, u16)) {
-        // The columnar menu does not need the cursor position
-    }
 }
 
 #[cfg(test)]

src/menu/ide_menu.rs

@@ -75,6 +75,14 @@ struct DefaultIdeMenuDetails {
     pub max_description_height: u16,
     /// Offset from the suggestion box to the description box
     pub description_offset: u16,
+    /// If true, the cursor pos will be corrected, so the suggestions match up with the typed text
+    /// ```text
+    /// C:\> str
+    ///      str join
+    ///      str trim
+    ///      str split
+    /// ```
+    pub correct_cursor_pos: bool,
 }
 
 impl Default for DefaultIdeMenuDetails {
@@ -91,6 +99,7 @@ impl Default for DefaultIdeMenuDetails {
             max_description_width: 50,
             max_description_height: 10,
             description_offset: 1,
+            correct_cursor_pos: false,
         }
     }
 }
@@ -114,6 +123,9 @@ struct IdeMenuDetails {
     pub space_right: u16,
     /// Corrected description offset, based on the available space
     pub description_offset: u16,
+    /// The ranges of the strings, the suggestions are based on (ranges in [`Editor::get_buffer`])
+    /// This is required to adjust the suggestion boxes position, when `correct_cursor_pos` in [`DefaultIdeMenuDetails`] is true
+    pub base_strings: Vec<String>,
 }
 
 /// Menu to present suggestions like similar to Ide completion menus
@@ -306,6 +318,13 @@ impl IdeMenu {
         self.default_details.description_offset = description_offset;
         self
     }
+
+    /// Menu builder with new correct cursor pos
+    #[must_use]
+    pub fn with_correct_cursor_pos(mut self, correct_cursor_pos: bool) -> Self {
+        self.default_details.correct_cursor_pos = correct_cursor_pos;
+        self
+    }
 }
 
 // Menu functionality
@@ -662,16 +681,16 @@ impl Menu for IdeMenu {
 
     /// Update menu values
     fn update_values(&mut self, editor: &mut Editor, completer: &mut dyn Completer) {
-        self.values = if self.only_buffer_difference {
+        let (values, base_ranges) = 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() {
-                    completer.complete(input, start + input.len())
+                    completer.complete_with_base_ranges(input, start + input.len())
                 } else {
-                    completer.complete("", editor.insertion_point())
+                    completer.complete_with_base_ranges("", editor.insertion_point())
                 }
             } else {
-                completer.complete("", editor.insertion_point())
+                completer.complete_with_base_ranges("", editor.insertion_point())
             }
         } else {
             // If there is a new line character in the line buffer, the completer
@@ -680,12 +699,18 @@ impl Menu for IdeMenu {
             // 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("\r\n", "  ").replace('\n', " ");
-            completer.complete(
+            completer.complete_with_base_ranges(
                 &trimmed_buffer[..editor.insertion_point()],
                 editor.insertion_point(),
             )
         };
 
+        self.values = values;
+        self.working_details.base_strings = base_ranges
+            .iter()
+            .map(|range| editor.get_buffer()[range.clone()].to_string())
+            .collect::<Vec<String>>();
+
         self.reset_position();
     }
 
@@ -739,7 +764,18 @@ impl Menu for IdeMenu {
             });
 
             let terminal_width = painter.screen_width();
-            let cursor_pos = self.working_details.cursor_col;
+            let mut cursor_pos = self.working_details.cursor_col;
+
+            if self.default_details.correct_cursor_pos {
+                let base_string = self
+                    .working_details
+                    .base_strings
+                    .iter()
+                    .min_by_key(|s| s.len())
+                    .cloned()
+                    .unwrap_or_default();
+                cursor_pos = cursor_pos.saturating_sub(base_string.width() as u16);
+            }
 
             let border_width = if self.default_details.border.is_some() {
                 2

src/menu/list_menu.rs

@@ -670,10 +670,6 @@ impl Menu for ListMenu {
     fn min_rows(&self) -> u16 {
         self.max_lines + 1
     }
-
-    fn set_cursor_pos(&mut self, _pos: (u16, u16)) {
-        // The list menu does not need the cursor position
-    }
 }
 
 fn number_of_lines(entry: &str, max_lines: usize, terminal_columns: u16) -> u16 {

src/menu/mod.rs

@@ -123,7 +123,9 @@ pub trait Menu: Send {
     /// Gets cached values from menu that will be displayed
     fn get_values(&self) -> &[Suggestion];
     /// Sets the position of the cursor (currently only required by the IDE menu)
-    fn set_cursor_pos(&mut self, pos: (u16, u16));
+    fn set_cursor_pos(&mut self, _pos: (u16, u16)) {
+        // empty implementation to make it optional
+    }
 }
 
 /// Allowed menus in Reedline