Prefer RopeSlice to &Rope in helix_core::syntax

Pascal and I discussed this and we think it's generally better to
take a 'RopeSlice' rather than a '&Rope'. The code block rendering
function in the markdown component module is a good example for how
this can be useful: we can remove an allocation of a rope and instead
directly turn a '&str' into a 'RopeSlice' which is very cheap.

A change to prefer 'RopeSlice' to '&Rope' whenever the rope isn't
modified would be nice, but it would be a very large diff (around 500+
500-). Starting off with just the syntax functions seems like a nice
middle-ground, and we can remove a Rope allocation because of it.

Co-authored-by: Pascal Kuthe <pascal.kuthe@semimod.de>

1 files changed, 7 insertions, 6 deletions

diff --git a/helix-core/src/transaction.rs b/helix-core/src/transaction.rs
index 9d2a3e5c..fec62578 100644
--- a/helix-core/src/transaction.rs
+++ b/helix-core/src/transaction.rs
@@ -1,3 +1,4 @@
+use ropey::RopeSlice;
 use smallvec::SmallVec;
 
 use crate::{Range, Rope, Selection, Tendril};
@@ -42,7 +43,7 @@ impl ChangeSet {
     }
 
     #[must_use]
-    pub fn new(doc: &Rope) -> Self {
+    pub fn new(doc: RopeSlice) -> Self {
         let len = doc.len_chars();
         Self {
             changes: Vec::new(),
@@ -485,7 +486,7 @@ impl Transaction {
     /// Create a new, empty transaction.
     pub fn new(doc: &Rope) -> Self {
         Self {
-            changes: ChangeSet::new(doc),
+            changes: ChangeSet::new(doc.slice(..)),
             selection: None,
         }
     }
@@ -946,9 +947,9 @@ mod test {
     #[test]
     fn combine_with_empty() {
         let empty = Rope::from("");
-        let a = ChangeSet::new(&empty);
+        let a = ChangeSet::new(empty.slice(..));
 
-        let mut b = ChangeSet::new(&empty);
+        let mut b = ChangeSet::new(empty.slice(..));
         b.insert("a".into());
 
         let changes = a.compose(b);
@@ -962,9 +963,9 @@ mod test {
         const TEST_CASE: &str = "Hello, これはヘリックスエディターです！";
 
         let empty = Rope::from("");
-        let a = ChangeSet::new(&empty);
+        let a = ChangeSet::new(empty.slice(..));
 
-        let mut b = ChangeSet::new(&empty);
+        let mut b = ChangeSet::new(empty.slice(..));
         b.insert(TEST_CASE.into());
 
         let changes = a.compose(b);