don't move cursor while forward deleting in append mode

Currently, when forward deleting (`delete_char_forward` bound to `del`,
`delete_word_forward`, `kill_to_line_end`) the cursor is moved to the
left in append mode (or generally when the cursor is at the end of the
selection). For example in a document `|abc|def`  (|indicates selection)
if enter append mode the cursor is moved to `c` and the selection
becomes: `|abcd|ef`. When deleting forward (`del`) `d` is deleted. The
expectation would be that the selection doesn't shrink so that `del`
again deletes `e` and then `f`. This would look as follows:

`|abcd|ef`
`|abce|f`
`|abcf|`
`|abc |`

This is inline with how other editors like kakoune work.
However, helix currently moves the selection backwards leading to the
following behavior:

`|abcd|ef`
`|abc|ef`
`|ab|ef`
`ef`

This means that `delete_char_forward` essentially acts like
`delete_char_backward` after deleting the first character in append
mode.

To fix the problem the cursor must be moved to the right while deleting
forward (first fix in this commit). Furthermore, when the EOF char is
reached a newline char must be inserted (just like when entering
appendmode) to prevent the cursor from moving to the right

1 files changed, 23 insertions, 0 deletions

diff --git a/helix-term/tests/test/commands.rs b/helix-term/tests/test/commands.rs
index 1efb204e..f91a6371 100644
--- a/helix-term/tests/test/commands.rs
+++ b/helix-term/tests/test/commands.rs
@@ -429,3 +429,26 @@ async fn test_delete_word_forward() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread")]
+async fn test_delete_char_forward() -> anyhow::Result<()> {
+    test((
+        platform_line(indoc! {"\
+                #[abc|]#def
+                #(abc|)#ef
+                #(abc|)#f
+                #(abc|)#
+            "})
+        .as_str(),
+        "a<del><esc>",
+        platform_line(indoc! {"\
+                #[abc|]#ef
+                #(abc|)#f
+                #(abc|)#
+                #(abc|)#
+            "})
+        .as_str(),
+    ))
+    .await?;
+
+    Ok(())
+}