Fix backwards selection duplication widening bug (#2945)

* Fix backwards selection duplication widening bug

* Add integration tests

* Make tests line-ending agnostic

Make tests line-ending agnostic

Use indoc to fix tests

Fix line-ending on test input

2 files changed, 44 insertions, 4 deletions

diff --git a/helix-term/src/commands.rs b/helix-term/src/commands.rs
index df4867fc..c9e35062 100644
--- a/helix-term/src/commands.rs
+++ b/helix-term/src/commands.rs
@@ -1411,16 +1411,16 @@ fn copy_selection_on_line(cx: &mut Context, direction: Direction) {
         let is_primary = *range == selection.primary();
 
         // The range is always head exclusive
-        let head = if range.anchor < range.head {
-            range.head - 1
+        let (head, anchor) = if range.anchor < range.head {
+            (range.head - 1, range.anchor)
         } else {
-            range.head
+            (range.head, range.anchor - 1)
         };
 
         let tab_width = doc.tab_width();
 
         let head_pos = visual_coords_at_pos(text, head, tab_width);
-        let anchor_pos = visual_coords_at_pos(text, range.anchor, tab_width);
+        let anchor_pos = visual_coords_at_pos(text, anchor, tab_width);
 
         let height = std::cmp::max(head_pos.row, anchor_pos.row)
             - std::cmp::min(head_pos.row, anchor_pos.row)
diff --git a/helix-term/tests/test/commands.rs b/helix-term/tests/test/commands.rs
index 0cd79bc7..f7ce9af0 100644
--- a/helix-term/tests/test/commands.rs
+++ b/helix-term/tests/test/commands.rs
@@ -91,3 +91,43 @@ async fn test_buffer_close_concurrent() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[tokio::test]
+async fn test_selection_duplication() -> anyhow::Result<()> {
+    // Forward
+    test((
+        platform_line(indoc! {"\
+            #[lo|]#rem
+            ipsum
+            dolor
+            "})
+        .as_str(),
+        "CC",
+        platform_line(indoc! {"\
+            #(lo|)#rem
+            #(ip|)#sum
+            #[do|]#lor
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    // Backward
+    test((
+        platform_line(indoc! {"\
+            #[|lo]#rem
+            ipsum
+            dolor
+            "})
+        .as_str(),
+        "CC",
+        platform_line(indoc! {"\
+            #(|lo)#rem
+            #(|ip)#sum
+            #[|do]#lor
+            "})
+        .as_str(),
+    ))
+    .await?;
+    Ok(())
+}