Remove selection when inserting a character

This happens when a placeholder is inserted with an LSP snippet.

helix-core/src/selection.rs

@@ -8,7 +8,7 @@ use crate::{
         prev_grapheme_boundary,
     },
     movement::Direction,
-    Assoc, ChangeSet, RopeGraphemes, RopeSlice,
+    Assoc, ChangeSet, RopeGraphemes, RopeSlice, Tendril,
 };
 use smallvec::{smallvec, SmallVec};
 use std::borrow::Cow;
@@ -329,6 +329,21 @@ impl Range {
         }
     }
 
+    /// Gets a range from [anchor, left-side block cursor].
+    #[must_use]
+    #[inline]
+    pub fn cursor_selection(self, text: RopeSlice) -> Range {
+        let head = self.cursor(text);
+        Range::new(std::cmp::min(self.anchor, head), head)
+    }
+
+    /// Gets a offset by tendril lenght, to be used with the cursor method.
+    #[must_use]
+    #[inline]
+    pub fn cursor_tendril_offset(self, tendril: &Tendril) -> Range {
+        Range::point(self.head + tendril.len() - (self.head - self.anchor))
+    }
+
     /// Puts the left side of the block cursor at `char_idx`, optionally extending.
     ///
     /// This follows "1-width" semantics, and therefore does a combination of anchor
@@ -592,7 +607,7 @@ impl Selection {
     /// Transforms the selection into all of the left-side head positions,
     /// using block-cursor semantics.
     pub fn cursors(self, text: RopeSlice) -> Self {
-        self.transform(|range| Range::point(range.cursor(text)))
+        self.transform(|range| range.cursor_selection(text))
     }
 
     pub fn fragments<'a>(&'a self, text: RopeSlice<'a>) -> impl Iterator<Item = Cow<str>> + 'a {

helix-core/src/transaction.rs

@@ -511,8 +511,13 @@ impl Transaction {
     /// Insert text at each selection head.
     pub fn insert(doc: &Rope, selection: &Selection, text: Tendril) -> Self {
         Self::change_by_selection(doc, selection, |range| {
-            (range.head, range.head, Some(text.clone()))
+            (range.anchor, range.head, Some(text.clone()))
         })
+        .with_selection(
+            selection
+                .clone()
+                .transform(|range| range.cursor_tendril_offset(&text)),
+        )
     }
 
     pub fn changes_iter(&self) -> ChangeIterator {