feat(diff): open editor at cursor line

- extend OpenExternalEditor event to carry an optional line number
- use the selection cursor index into the flat line list to find the
  exact line, using the same index space as selected_lines()
- add editor_goto_style() to map editor name to the correct
  goto-line argument style (hx: file:line, code: --goto file:line,
  vi/vim/nvim/emacs/nano/etc: +line file)

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Code 2.1.143 (Claude Code)
Signed-Off-By: Paal Øye-Strømme <paal.o.eye@gmail.com>

src/app.rs

@@ -119,6 +119,7 @@ pub struct App {
 	// "Flags"
 	requires_redraw: Cell<bool>,
 	file_to_open: Option<String>,
+	line_to_open: Option<u32>,
 }
 
 pub struct Environment {
@@ -244,6 +245,7 @@ impl App {
 			key_config: env.key_config,
 			requires_redraw: Cell::new(false),
 			file_to_open: None,
+			line_to_open: None,
 			repo: env.repo,
 			repo_path_text,
 			popup_stack: PopupStack::default(),
@@ -376,6 +378,7 @@ impl App {
 						ExternalEditorPopup::open_file_in_editor(
 							&self.repo.borrow(),
 							Path::new(&path),
+							self.line_to_open.take(),
 						)
 					} else {
 						let changes =
@@ -815,10 +818,11 @@ impl App {
 					flags.insert(NeedsUpdate::ALL);
 				}
 			}
-			InternalEvent::OpenExternalEditor(path) => {
+			InternalEvent::OpenExternalEditor(path, line) => {
 				self.input.set_polling(false);
 				self.external_editor_popup.show()?;
 				self.file_to_open = path;
+				self.line_to_open = line;
 				flags.insert(NeedsUpdate::COMMANDS);
 			}
 			InternalEvent::Push(branch, push_type, force, delete) => {

src/components/diff.rs

@@ -888,10 +888,32 @@ impl Component for DiffComponent {
 				} else if key_match(e, self.key_config.keys.edit_file)
 					&& self.can_edit_file()
 				{
+					let line = self.diff.as_ref().and_then(|d| {
+						let cursor = self.selection.get_start();
+						// walk the flat line list to the cursor position,
+						// same index space as selected_lines()
+						d.hunks
+							.iter()
+							.flat_map(|h| h.lines.iter())
+							.nth(cursor)
+							.and_then(|l| l.position.new_lineno)
+							.or_else(|| {
+								// cursor is on a deletion — use old_lineno
+								// as a best-effort fallback
+								d.hunks
+									.iter()
+									.flat_map(|h| h.lines.iter())
+									.nth(cursor)
+									.and_then(|l| {
+										l.position.old_lineno
+									})
+							})
+					});
 					self.queue.push(
-						InternalEvent::OpenExternalEditor(Some(
-							self.current.path.clone(),
-						)),
+						InternalEvent::OpenExternalEditor(
+							Some(self.current.path.clone()),
+							line,
+						),
 					);
 					Ok(EventState::Consumed)
 				} else if key_match(
@@ -1055,7 +1077,7 @@ mod tests {
 		let event = env.queue.pop();
 		assert!(matches!(
 			event,
-			Some(InternalEvent::OpenExternalEditor(Some(path)))
+			Some(InternalEvent::OpenExternalEditor(Some(path), _))
 				if path == "src/main.rs"
 		));
 	}

src/components/revision_files.rs

@@ -524,7 +524,10 @@ impl Component for RevisionFilesComponent {
 					// not altering a file inside a revision here
 					self.queue.push(InternalEvent::TabSwitchStatus);
 					self.queue.push(
-						InternalEvent::OpenExternalEditor(Some(file)),
+						InternalEvent::OpenExternalEditor(
+							Some(file),
+							None,
+						),
 					);
 					return Ok(EventState::Consumed);
 				}

src/components/status_tree.rs

@@ -509,9 +509,10 @@ impl Component for StatusTreeComponent {
 				{
 					if let Some(status_item) = self.selection_file() {
 						self.queue.push(
-							InternalEvent::OpenExternalEditor(Some(
-								status_item.path,
-							)),
+							InternalEvent::OpenExternalEditor(
+								Some(status_item.path),
+								None,
+							),
 						);
 					}
 					Ok(EventState::Consumed)

src/popups/commit.rs

@@ -189,6 +189,7 @@ impl CommitPopup {
 		ExternalEditorPopup::open_file_in_editor(
 			&self.repo.borrow(),
 			&file_path,
+			None,
 		)?;
 
 		let mut message = String::new();
@@ -587,7 +588,9 @@ impl Component for CommitPopup {
 						self.key_config.keys.open_commit_editor,
 					) {
 						self.queue.push(
-							InternalEvent::OpenExternalEditor(None),
+							InternalEvent::OpenExternalEditor(
+								None, None,
+							),
 						);
 						self.hide();
 						true

src/popups/externaleditor.rs

@@ -27,6 +27,28 @@ use scopeguard::defer;
 use std::ffi::OsStr;
 use std::{env, io, path::Path, process::Command};
 
+enum EditorGoto {
+	None,
+	PlusLine(u32),
+	FileColon(u32),
+	GotoFlag(u32),
+}
+
+fn editor_goto_style(command: &str, line: Option<u32>) -> EditorGoto {
+	let Some(ln) = line else {
+		return EditorGoto::None;
+	};
+	let cmd = command.to_lowercase();
+	if cmd.ends_with("hx") {
+		EditorGoto::FileColon(ln)
+	} else if cmd.ends_with("code") || cmd.ends_with("code-insiders")
+	{
+		EditorGoto::GotoFlag(ln)
+	} else {
+		EditorGoto::PlusLine(ln)
+	}
+}
+
 ///
 pub struct ExternalEditorPopup {
 	visible: bool,
@@ -44,10 +66,11 @@ impl ExternalEditorPopup {
 		}
 	}
 
-	/// opens file at given `path` in an available editor
+	/// opens file at given `path` in an available editor, optionally at `line`
 	pub fn open_file_in_editor(
 		repo: &RepoPath,
 		path: &Path,
+		line: Option<u32>,
 	) -> Result<()> {
 		let work_dir = repo_work_dir(repo)?;
 
@@ -107,7 +130,32 @@ impl ExternalEditorPopup {
 		let mut args: Vec<&OsStr> =
 			remainder.map(OsStr::new).collect();
 
-		args.push(path.as_os_str());
+		let line_arg: String;
+		let helix_path: std::path::PathBuf;
+		match editor_goto_style(&command, line) {
+			EditorGoto::None => {
+				args.push(path.as_os_str());
+			}
+			EditorGoto::PlusLine(ln) => {
+				line_arg = format!("+{ln}");
+				args.push(OsStr::new(&line_arg));
+				args.push(path.as_os_str());
+			}
+			EditorGoto::FileColon(ln) => {
+				helix_path = path.with_file_name(format!(
+					"{}:{ln}",
+					path.file_name()
+						.unwrap_or_default()
+						.to_string_lossy(),
+				));
+				args.push(helix_path.as_os_str());
+			}
+			EditorGoto::GotoFlag(ln) => {
+				args.push(OsStr::new("--goto"));
+				line_arg = format!("{}:{ln}", path.to_string_lossy());
+				args.push(OsStr::new(&line_arg));
+			}
+		}
 
 		Command::new(command.clone())
 			.current_dir(work_dir)

src/queue.rs

@@ -121,7 +121,7 @@ pub enum InternalEvent {
 	///
 	SelectBranch,
 	///
-	OpenExternalEditor(Option<String>),
+	OpenExternalEditor(Option<String>, Option<u32>),
 	///
 	Push(String, PushType, bool, bool),
 	///