Resolve issue when user tries to swap the top or bottom line with a l…

CHANGELOG.md

@@ -6,6 +6,7 @@
 * Disabled continuous deployment in GHA. See `.github/workflows/build_artifact.yml`
 for details
 
+* Resolve crash when user tries to switch top or bottom line outside of scope
 * Resolved crash when the user tries to `delete word` past the end of a line
 
 ### v0.0.3 | 17/Mar/2026

src/action.h

@@ -267,17 +267,17 @@ template <typename T, typename U>
             auto logger = spdlog::get("basic_logger");
             if (logger != nullptr) { logger->info("Action called: MoveLineDown"); }
 
-            v->get_active_model()->move_line_down();
-            v->cursor_down();
+            bool actionable = v->get_active_model()->move_line_down();
+            if (actionable) { v->cursor_down(); }
             return {};
         } break;
 
         case ActionType::MoveLineUp: {
             auto logger = spdlog::get("basic_logger");
             if (logger != nullptr) { logger->info("Action called: MoveLineUp"); }
 
-            v->get_active_model()->move_line_up();
-            v->cursor_up();
+            bool actionable = v->get_active_model()->move_line_up();
+            if (actionable) { v->cursor_up(); }
             return {};
         } break;
 

src/model.cpp

@@ -424,12 +424,16 @@ void Model::toggle_case() {
     return false;
 }
 
-void Model::move_line_down() {
+[[nodiscard]] bool Model::move_line_down() {
+    if (current_line == buf.size() - 1) { return false; }
     std::iter_swap(buf.begin() + current_line, buf.begin() + current_line + 1);
+    return true;
 }
 
-void Model::move_line_up() {
+[[nodiscard]] bool Model::move_line_up() {
+    if (!current_line) { return false; }
     std::iter_swap(buf.begin() + current_line, buf.begin() + current_line - 1);
+    return true;
 }
 
 void Model::set_read_only(std::string_view file) {

src/model.h

@@ -62,8 +62,8 @@ struct Model {
     [[nodiscard]] bool undo(const int);
     [[nodiscard]] char get_current_char() const;
     [[nodiscard]] bool redo(const int);
-    void move_line_down();
-    void move_line_up();
+    [[nodiscard]] bool move_line_down();
+    [[nodiscard]] bool move_line_up();
     void set_read_only(std::string_view);
     void delete_current_line();
     [[nodiscard]] const std::optional<WordPos> current_word() const;

tests/integration/normal_mode_test.py

@@ -430,6 +430,27 @@ def test_upper_k_key(r: TmuxRunner):
     assert "here is a newline and a tab" in r.lines()[2]
 
 
+@setup("tests/fixture/test_file_1.txt")
+def test_upper_j_key_end_of_file(r: TmuxRunner):
+    r.press("G")
+    r.press("J")
+
+    # Check nothing has changed
+    # TODO: replace with r.MODIFIED_MARKER
+    assert "[X]" not in r.statusbar_parts()
+    assert len(r.statusbar_parts())
+
+
+@setup("tests/fixture/test_file_1.txt")
+def test_upper_k_key_start_of_file(r: TmuxRunner):
+    r.press("K")
+
+    # Check nothing has changed
+    # TODO: replace with r.MODIFIED_MARKER
+    assert "[X]" not in r.statusbar_parts()
+    assert len(r.statusbar_parts())
+
+
 @setup("tests/fixture/test_file_1.txt")
 def test_tt_key(r: TmuxRunner):
     r.type_str("tt")