Support negative line numbers for goto

crates/edit/src/bin/edit/documents.rs

@@ -105,6 +105,20 @@ impl Document {
 
         None
     }
+
+    /// Moves the cursor to a 1-based line/char position.
+    /// A negative line counts backwards from the end
+    /// of the document, e.g. -1 is the last line.
+    pub fn cursor_move_to_goto(&self, goto: Point) {
+        let mut tb = self.buffer.borrow_mut();
+        let x = goto.x.saturating_sub(1);
+        let y = if goto.y < 0 {
+            tb.logical_line_count().saturating_add(goto.y)
+        } else {
+            goto.y.saturating_sub(1)
+        };
+        tb.cursor_move_to_logical(Point { x, y });
+    }
 }
 
 #[derive(Default)]
@@ -281,22 +295,26 @@ impl DocumentManager {
 }
 
 /// Parse a filename in the form of "filename:line:char".
-/// Returns the position of the first colon and the line/char coordinates.
+/// Returns the filename and the [`Document::cursor_move_to_goto`] coordinates.
 pub fn parse_filename_goto(path: &Path) -> (&Path, Option<Point>) {
     fn parse(s: &[u8]) -> Option<CoordType> {
-        if s.is_empty() {
+        let (negative, digits) = match s {
+            [b'-', rest @ ..] => (true, rest),
+            _ => (false, s),
+        };
+        if digits.is_empty() {
             return None;
         }
 
         let mut num: CoordType = 0;
-        for &b in s {
+        for &b in digits {
             if !b.is_ascii_digit() {
                 return None;
             }
             let digit = (b - b'0') as CoordType;
             num = num.checked_mul(10)?.checked_add(digit)?;
         }
-        Some(num)
+        Some(if negative { -num } else { num })
     }
 
     fn find_colon_rev(bytes: &[u8], offset: usize) -> Option<usize> {
@@ -315,19 +333,19 @@ pub fn parse_filename_goto(path: &Path) -> (&Path, Option<Point>) {
         Some(last) => last,
         None => return (path, None),
     };
-    let last = (last - 1).max(0);
     let mut len = colend;
-    let mut goto = Point { x: 0, y: last };
+    let mut goto = Point { x: 1, y: last };
 
-    if let Some(colbeg) = find_colon_rev(bytes, colend) {
+    // Counting backwards is only supported for lines,
+    // so a negative `last` rules out a char position.
+    if last >= 0
+        && let Some(colbeg) = find_colon_rev(bytes, colend)
         // Same here: Don't allow empty filenames.
-        if colbeg != 0
-            && let Some(first) = parse(&bytes[colbeg + 1..colend])
-        {
-            let first = (first - 1).max(0);
-            len = colbeg;
-            goto = Point { x: last, y: first };
-        }
+        && colbeg != 0
+        && let Some(first) = parse(&bytes[colbeg + 1..colend])
+    {
+        len = colbeg;
+        goto = Point { x: last, y: first };
     }
 
     // Strip off the :line:char suffix.
@@ -351,20 +369,24 @@ mod tests {
         assert_eq!(parse("123"), ("123", None));
         assert_eq!(parse("abc"), ("abc", None));
         assert_eq!(parse(":123"), (":123", None));
-        assert_eq!(parse("abc:123"), ("abc", Some(Point { x: 0, y: 122 })));
-        assert_eq!(parse("45:123"), ("45", Some(Point { x: 0, y: 122 })));
-        assert_eq!(parse(":45:123"), (":45", Some(Point { x: 0, y: 122 })));
-        assert_eq!(parse("abc:45:123"), ("abc", Some(Point { x: 122, y: 44 })));
-        assert_eq!(parse("abc:def:123"), ("abc:def", Some(Point { x: 0, y: 122 })));
-        assert_eq!(parse("1:2:3"), ("1", Some(Point { x: 2, y: 1 })));
-        assert_eq!(parse("::3"), (":", Some(Point { x: 0, y: 2 })));
-        assert_eq!(parse("1::3"), ("1:", Some(Point { x: 0, y: 2 })));
+        assert_eq!(parse("abc:123"), ("abc", Some(Point { x: 1, y: 123 })));
+        assert_eq!(parse("45:123"), ("45", Some(Point { x: 1, y: 123 })));
+        assert_eq!(parse(":45:123"), (":45", Some(Point { x: 1, y: 123 })));
+        assert_eq!(parse("abc:45:123"), ("abc", Some(Point { x: 123, y: 45 })));
+        assert_eq!(parse("abc:def:123"), ("abc:def", Some(Point { x: 1, y: 123 })));
+        assert_eq!(parse("1:2:3"), ("1", Some(Point { x: 3, y: 2 })));
+        assert_eq!(parse("::3"), (":", Some(Point { x: 1, y: 3 })));
+        assert_eq!(parse("1::3"), ("1:", Some(Point { x: 1, y: 3 })));
         assert_eq!(parse(""), ("", None));
         assert_eq!(parse(":"), (":", None));
         assert_eq!(parse("::"), ("::", None));
-        assert_eq!(parse("a:1"), ("a", Some(Point { x: 0, y: 0 })));
+        assert_eq!(parse("a:1"), ("a", Some(Point { x: 1, y: 1 })));
         assert_eq!(parse("1:a"), ("1:a", None));
-        assert_eq!(parse("file.txt:10"), ("file.txt", Some(Point { x: 0, y: 9 })));
-        assert_eq!(parse("file.txt:10:5"), ("file.txt", Some(Point { x: 4, y: 9 })));
+        assert_eq!(parse("file.txt:10"), ("file.txt", Some(Point { x: 1, y: 10 })));
+        assert_eq!(parse("file.txt:10:5"), ("file.txt", Some(Point { x: 5, y: 10 })));
+        assert_eq!(parse("file.txt:-1"), ("file.txt", Some(Point { x: 1, y: -1 })));
+        assert_eq!(parse("file.txt:-10:5"), ("file.txt", Some(Point { x: 5, y: -10 })));
+        assert_eq!(parse("file.txt:10:-5"), ("file.txt:10", Some(Point { x: 1, y: -5 })));
+        assert_eq!(parse("file.txt:-"), ("file.txt:-", None));
     }
 }

crates/edit/src/bin/edit/draw_editor.rs

@@ -1,8 +1,6 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-use std::num::ParseIntError;
-
 use edit::framebuffer::IndexedColor;
 use edit::helpers::*;
 use edit::icu;
@@ -319,14 +317,12 @@ pub fn draw_goto_menu(ctx: &mut Context, state: &mut State) {
             ctx.steal_focus();
 
             if ctx.consume_shortcut(vk::RETURN) {
-                match validate_goto_point(&state.goto_target) {
-                    Ok(point) => {
-                        let mut buf = doc.buffer.borrow_mut();
-                        buf.cursor_move_to_logical(point);
-                        buf.make_cursor_visible();
-                        done = true;
-                    }
-                    Err(_) => state.goto_invalid = true,
+                if let Some(goto) = validate_goto_point(&state.goto_target) {
+                    doc.cursor_move_to_goto(goto);
+                    doc.buffer.borrow_mut().make_cursor_visible();
+                    done = true;
+                } else {
+                    state.goto_invalid = true;
                 }
                 ctx.needs_rerender();
             }
@@ -344,13 +340,17 @@ pub fn draw_goto_menu(ctx: &mut Context, state: &mut State) {
     }
 }
 
-fn validate_goto_point(line: &str) -> Result<Point, ParseIntError> {
+fn validate_goto_point(line: &str) -> Option<Point> {
     let mut coords = [0; 2];
-    let (y, x) = line.split_once(':').unwrap_or((line, "0"));
+    let (y, x) = line.split_once(':').unwrap_or((line, "1"));
     // Using a loop here avoids 2 copies of the str->int code.
     // This makes the binary more compact.
     for (i, s) in [x, y].iter().enumerate() {
-        coords[i] = s.parse::<CoordType>()?.saturating_sub(1);
+        coords[i] = s.parse::<CoordType>().ok()?;
+    }
+    // Counting backwards is only supported for lines.
+    if coords[0] < 1 {
+        return None;
     }
-    Ok(Point { x: coords[0], y: coords[1] })
+    Some(Point { x: coords[0], y: coords[1] })
 }

crates/edit/src/bin/edit/main.rs

@@ -291,7 +291,7 @@ fn handle_args(state: &mut State) -> apperr::Result<bool> {
     for (p, goto) in &paths {
         let doc = state.documents.add_file_path(p)?;
         if let Some(goto) = goto {
-            doc.buffer.borrow_mut().cursor_move_to_logical(*goto);
+            doc.cursor_move_to_goto(*goto);
         }
     }