Add command to merge non-consecutive ranges (#7053)

* Add command for merging non-consecutive ranges

* Add `merge_selections` command to book

* Simplify `merge_ranges`

Heeded the advice of @the-mikedavis to stop iterating over all ranges and simply merge the first and the last range, as the invariants of `Selection` guarantee that the list of ranges is always sorted and never empty.

* Clarify doc comment of `merge_ranges`

book/src/keymap.md

@@ -111,6 +111,7 @@
 | `s`                   | Select all regex matches inside selections                        | `select_regex`                       |
 | `S`                   | Split selection into sub selections on regex matches              | `split_selection`                    |
 | `Alt-s`               | Split selection on newlines                                       | `split_selection_on_newline`         |
+| `Alt-minus`           | Merge selections                                                  | `merge_selections`                   |
 | `Alt-_`               | Merge consecutive selections                                      | `merge_consecutive_selections`       |
 | `&`                   | Align selection in columns                                        | `align_selections`                   |
 | `_`                   | Trim whitespace from the selection                                | `trim_selections`                    |

helix-core/src/selection.rs

@@ -522,7 +522,14 @@ impl Selection {
         self
     }
 
-    // Merges all ranges that are consecutive
+    /// Replaces ranges with one spanning from first to last range.
+    pub fn merge_ranges(self) -> Self {
+        let first = self.ranges.first().unwrap();
+        let last = self.ranges.last().unwrap();
+        Selection::new(smallvec![first.merge(*last)], 0)
+    }
+
+    /// Merges all ranges that are consecutive.
     pub fn merge_consecutive_ranges(mut self) -> Self {
         let mut primary = self.ranges[self.primary_index];
 

helix-term/src/commands.rs

@@ -275,6 +275,7 @@ impl MappableCommand {
         select_regex, "Select all regex matches inside selections",
         split_selection, "Split selections on regex matches",
         split_selection_on_newline, "Split selection on newlines",
+        merge_selections, "Merge selections",
         merge_consecutive_selections, "Merge consecutive selections",
         search, "Search for regex pattern",
         rsearch, "Reverse search for regex pattern",
@@ -1737,6 +1738,12 @@ fn split_selection_on_newline(cx: &mut Context) {
     doc.set_selection(view.id, selection);
 }
 
+fn merge_selections(cx: &mut Context) {
+    let (view, doc) = current!(cx.editor);
+    let selection = doc.selection(view.id).clone().merge_ranges();
+    doc.set_selection(view.id, selection);
+}
+
 fn merge_consecutive_selections(cx: &mut Context) {
     let (view, doc) = current!(cx.editor);
     let selection = doc.selection(view.id).clone().merge_consecutive_ranges();

helix-term/src/keymap/default.rs

@@ -79,6 +79,7 @@ pub fn default() -> HashMap<Mode, Keymap> {
 
         "s" => select_regex,
         "A-s" => split_selection_on_newline,
+        "A-minus" => merge_selections,
         "A-_" => merge_consecutive_selections,
         "S" => split_selection,
         ";" => collapse_selection,