feat: expand completion snippets and navigate placeholders

src/tui.rs

@@ -340,6 +340,7 @@ fn translate(key: KeyEvent) -> Option<Input> {
         KeyCode::Home => Input::Home,
         KeyCode::End => Input::End,
         KeyCode::Tab => Input::Char('\t'),
+        KeyCode::BackTab => Input::BackTab,
         _ => return None,
     })
 }
@@ -683,7 +684,11 @@ fn draw(
                 }
             }
         }
-        for selection in selections.iter().filter(|_| !editor.visual_linewise()) {
+        for selection in selections
+            .iter()
+            .filter(|_| !editor.visual_linewise())
+            .chain(editor.snippet_selections())
+        {
             let first = selection.start.row.max(*top);
             let last = selection.end.row.min(top.saturating_add(height - 1));
             let style = Style::default().fg(Color::White).bg(Color::Blue);
@@ -1583,6 +1588,8 @@ fn semantic_style(token: &SemanticToken) -> Style {
 }
 
 #[cfg(test)]
+// These fixtures intentionally contain ranges, not lists of indices.
+#[allow(clippy::single_range_in_vec_init)]
 mod tests {
     use super::*;
     use std::{
@@ -1643,6 +1650,7 @@ mod tests {
                     detail: Some("\tTAIL".into()),
                     primary_edit: 0,
                     edits: vec![],
+                    snippet: None,
                 })
                 .collect(),
             selected: 20,
@@ -1707,6 +1715,78 @@ mod tests {
         }
     }
 
+    #[test]
+    fn snippet_highlight_tracks_argument_graphemes_without_filling_the_row() {
+        use crate::plugin::{
+            CompletionEdit, CompletionItem, CompletionSnippet, SnippetTabstop, TextPosition,
+        };
+        let mut editor = Editor::open(None, vec![]).unwrap();
+        editor.handle(Input::Char('i'));
+        editor
+            .show_completion(vec![CompletionItem {
+                label: "call".into(),
+                detail: None,
+                primary_edit: 0,
+                edits: vec![CompletionEdit {
+                    start: TextPosition { row: 0, column: 0 },
+                    end: TextPosition { row: 0, column: 0 },
+                    text: "call(界e\u{301}, tail)".into(),
+                }],
+                snippet: Some(CompletionSnippet {
+                    tabstops: vec![
+                        SnippetTabstop {
+                            index: 1,
+                            ranges: vec![5..11],
+                            ancestors: vec![vec![]],
+                        },
+                        SnippetTabstop {
+                            index: 2,
+                            ranges: vec![13..17],
+                            ancestors: vec![vec![]],
+                        },
+                        SnippetTabstop {
+                            index: 0,
+                            ranges: vec![18..18],
+                            ancestors: vec![vec![]],
+                        },
+                    ],
+                }),
+            }])
+            .unwrap();
+        let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(28, 6)).unwrap();
+        let mut viewports = BufferViewports::default();
+        for (key, selected, caret) in [
+            (None, 7..10, Position::new(7, 0)),
+            (Some(Input::Char('\t')), 12..16, Position::new(12, 0)),
+        ] {
+            if let Some(key) = key {
+                editor.handle(key);
+            }
+            terminal
+                .draw(|frame| viewports.draw(frame, &editor))
+                .unwrap();
+            let buffer = terminal.backend().buffer();
+            // A wide glyph's leading cell owns its terminal style.
+            for x in (0..28).filter(|x| *x != 8) {
+                assert_eq!(
+                    buffer[(x, 0)].bg == Color::Blue,
+                    selected.contains(&x),
+                    "column {x}, selection {:?}, screen:\n{}",
+                    editor.snippet_selections(),
+                    screen_text(&terminal),
+                );
+            }
+            assert_eq!(terminal.get_cursor_position().unwrap(), caret);
+        }
+        editor.handle(Input::Escape);
+        terminal
+            .draw(|frame| viewports.draw(frame, &editor))
+            .unwrap();
+        for x in 0..28 {
+            assert_ne!(terminal.backend().buffer()[(x, 0)].bg, Color::Blue);
+        }
+    }
+
     #[test]
     fn hover_shows_more_documentation_with_markdown_and_fenced_code_colors() {
         let mut editor = Editor::open(None, vec![]).unwrap();