transaction: Also modify map_pos to work with insert|delete order.

helix-core/src/transaction.rs

@@ -335,7 +335,7 @@ impl ChangeSet {
                 Delete(i) | Retain(i) => *i,
                 Insert(_) => 0,
             };
-            let old_end = old_pos + len;
+            let mut old_end = old_pos + len;
 
             match change {
                 Retain(_) => {
@@ -345,29 +345,28 @@ impl ChangeSet {
                     new_pos += len;
                 }
                 Delete(_) => {
-                    // a subsequent ins means a replace, consume it
-                    let ins = if let Some(Insert(s)) = iter.peek() {
-                        iter.next();
-                        s.chars().count()
-                    } else {
-                        0
-                    };
-
                     // in range
+                    if old_end > pos {
+                        return new_pos;
+                    }
+                }
+                Insert(s) => {
+                    let ins = s.chars().count();
+
+                    // a subsequent delete means a replace, consume it
+                    if let Some(Delete(len)) = iter.peek() {
+                        old_end = old_pos + len;
+                        // in range of replaced text
                         if old_end > pos {
                             // at point or tracking before
                             if pos == old_pos || assoc == Assoc::Before {
                                 return new_pos;
                             } else {
-                            // place to end of delete
+                                // place to end of insert
                                 return new_pos + ins;
                             }
                         }
-
-                    new_pos += ins;
-                }
-                Insert(s) => {
-                    let ins = s.chars().count();
+                    } else {
                         // at insert point
                         if old_pos == pos {
                             // return position before inserted text
@@ -378,6 +377,7 @@ impl ChangeSet {
                                 return new_pos + ins;
                             }
                         }
+                    }
 
                     new_pos += ins;
                 }
@@ -602,10 +602,10 @@ mod test {
         // stays inbetween replacements
         let cs = ChangeSet {
             changes: vec![
-                Delete(2),
                 Insert("ab".into()),
                 Delete(2),
                 Insert("cd".into()),
+                Delete(2),
             ],
             len: 4,
         };