edit prediction: Try to fix panic in `Buffer::preview_edits` (#24654)

Bennet Bo Fenner and Antonio created 11 months ago

We've seen a few crashes in `SyntaxSnapshot::reparse_with_ranges` during
`Buffer::preview_edits`, where an offset conversion fails because it is
out of range.
We are not sure how exactly this is happening. 
Our theory is that the syntax snapshot is using an outdated state when
edits happen in the meantime (while interpolating). This is an attempt
to see if it helps with the panics, hopefully we can revisit this when
we have a better understanding of the issue.


Co-Authored-by: Antonio <[e-mail]>

Release Notes:

- N/A

Co-authored-by: Antonio <[e-mail]>

Change summary

crates/language/src/buffer.rs | 4 ++++
1 file changed, 4 insertions(+)

Detailed changes

crates/language/src/buffer.rs

@@ -1102,6 +1102,10 @@ impl Buffer {
         let mut syntax_snapshot = self.syntax_map.lock().snapshot();
         cx.background_executor().spawn(async move {
             if !edits.is_empty() {
+                if let Some(language) = language.clone() {
+                    syntax_snapshot.reparse(&old_snapshot, registry.clone(), language);
+                }
+
                 branch_buffer.edit(edits.iter().cloned());
                 let snapshot = branch_buffer.snapshot();
                 syntax_snapshot.interpolate(&snapshot);