From 6de370cb73efb73c3536823a37c56df053e4d783 Mon Sep 17 00:00:00 2001
From: Alan Zimmerman <alanzimm@meta.com>
Date: Fri, 12 Jul 2024 09:01:40 -0700
Subject: [PATCH] Protect against panics from DidChangeTextDocument

Summary: These panics were generated by experimenting with emacs.

Reviewed By: jcpetruzza

Differential Revision: D59684333

fbshipit-source-id: d4bf59614491d04d4b5e38b03eb44ccca6dc5a84
---
 crates/elp/src/document.rs      | 20 ++++++++++++++++----
 crates/ide_db/src/line_index.rs |  7 ++++++-
 2 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/crates/elp/src/document.rs b/crates/elp/src/document.rs
index 54338f1116..d7b126fb6f 100644
--- a/crates/elp/src/document.rs
+++ b/crates/elp/src/document.rs
@@ -12,7 +12,7 @@ use std::ops::Range;
 use elp_ide::elp_ide_db::LineIndex;
 use lsp_types::TextDocumentContentChangeEvent;
 
-use crate::from_proto::text_range;
+use crate::from_proto::safe_text_range;
 use crate::line_endings::LineEndings;
 
 pub struct Document {
@@ -71,9 +71,21 @@ impl Document {
                         line_index = LineIndex::new(&self.content);
                     }
                     index_valid = IndexValid::UpToLineExclusive(range.start.line);
-                    let range = text_range(&line_index, range);
-                    self.content
-                        .replace_range(Range::<usize>::from(range), &change.text);
+                    if let Some(range) = safe_text_range(&line_index, range) {
+                        if self.content.is_char_boundary(range.start().into())
+                            && self.content.is_char_boundary(range.end().into())
+                        {
+                            self.content
+                                .replace_range(Range::<usize>::from(range), &change.text);
+                        } else {
+                            log::warn!(
+                                "discarding invalid document change char boundary: {:?}",
+                                &change
+                            );
+                        }
+                    } else {
+                        log::warn!("discarding invalid document change range: {:?}", &change);
+                    }
                 }
                 None => {
                     self.content = change.text;
diff --git a/crates/ide_db/src/line_index.rs b/crates/ide_db/src/line_index.rs
index 8fa140b95c..233dafcae4 100644
--- a/crates/ide_db/src/line_index.rs
+++ b/crates/ide_db/src/line_index.rs
@@ -120,7 +120,12 @@ impl LineIndex {
     pub fn offset(&self, line_col: LineCol) -> TextSize {
         //FIXME: return Result
         let col = self.utf16_to_utf8_col(line_col.line, line_col.col_utf16);
-        self.newlines[line_col.line as usize] + col
+        if let Some(offset) = self.newlines.get(line_col.line as usize) {
+            offset + col
+        } else {
+            log::warn!("line_index.offset, limiting");
+            self.newlines[self.newlines.len() - 1] + col
+        }
     }
 
     pub fn safe_offset(&self, line_col: LineCol) -> Option<TextSize> {