Fix panic with completion ranges and autoclose regions interop (#35408)

As reported [in
Discord](https://discord.com/channels/869392257814519848/1106226198494859355/1398470747227426948)
C projects with `"` as "brackets" that autoclose, may invoke panics when
edited at the end of the file.

With a single selection-caret (`ˇ`), at the end of the file,
```c
ifndef BAR_H
#define BAR_H

#include <stdbool.h>

int fn_branch(bool do_branch1, bool do_branch2);

#endif // BAR_H
#include"ˇ"
```
gets an LSP response from clangd
```jsonc
{
  "filterText": "AGL/",
  "insertText": "AGL/",
  "insertTextFormat": 1,
  "kind": 17,
  "label": " AGL/",
  "labelDetails": {},
  "score": 0.78725427389144897,
  "sortText": "40b67681AGL/",
  "textEdit": {
    "newText": "AGL/",
    "range": { "end": { "character": 11, "line": 8 }, "start": { "character": 10, "line": 8 } }
  }
}
```

which replaces `"` after the caret (character/column 11, 0-indexed).
This is reasonable, as regular follow-up (proposed in further
completions), is a suffix + a closing `"`:

<img width="842" height="259" alt="image"
src="https://github.com/user-attachments/assets/ea56f621-7008-4ce2-99ba-87344ddf33d2"
/>

Yet when Zed handles user input of `"`, it panics due to multiple
reasons:

* after applying any snippet text edit, Zed did a selection change:
5537987630/crates/editor/src/editor.rs (L9539-L9545)
which caused eventual autoclose region invalidation:
5537987630/crates/editor/src/editor.rs (L2970)

This covers all cases that insert the `include""` text.

* after applying any user input and "plain" text edit, Zed did not
invalidate any autoclose regions at all, relying on the "bracket" (which
includes `"`) autoclose logic to rule edge cases out

* bracket autoclose logic detects previous `"` and considers the new
user input as a valid closure, hence no autoclose region needed.
But there is an autoclose bracket data after the plaintext completion
insertion (`AGL/`) really, and it's not invalidated after `"` handling

* in addition to that, `Anchor::is_valid` method in `text` panicked, and
required `fn try_fragment_id_for_anchor` to handle "pointing at odd,
after the end of the file, offset" cases as `false`

A test reproducing the feedback and 2 fixes added: proper, autoclose
region invalidation call which required the invalidation logic tweaked a
bit, and "superficial", "do not apply bad selections that cause panics"
fix in the editor to be more robust

Release Notes:

- Fixed panic with completion ranges and autoclose regions interop

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

Cargo.lock

@@ -4920,6 +4920,7 @@ dependencies = [
  "theme",
  "time",
  "tree-sitter-bash",
+ "tree-sitter-c",
  "tree-sitter-html",
  "tree-sitter-python",
  "tree-sitter-rust",

crates/editor/Cargo.toml

@@ -22,6 +22,7 @@ test-support = [
     "theme/test-support",
     "util/test-support",
     "workspace/test-support",
+    "tree-sitter-c",
     "tree-sitter-rust",
     "tree-sitter-typescript",
     "tree-sitter-html",
@@ -76,6 +77,7 @@ telemetry.workspace = true
 text.workspace = true
 time.workspace = true
 theme.workspace = true
+tree-sitter-c = { workspace = true, optional = true }
 tree-sitter-html = { workspace = true, optional = true }
 tree-sitter-rust = { workspace = true, optional = true }
 tree-sitter-typescript = { workspace = true, optional = true }
@@ -106,6 +108,7 @@ settings = { workspace = true, features = ["test-support"] }
 tempfile.workspace = true
 text = { workspace = true, features = ["test-support"] }
 theme = { workspace = true, features = ["test-support"] }
+tree-sitter-c.workspace = true
 tree-sitter-html.workspace = true
 tree-sitter-rust.workspace = true
 tree-sitter-typescript.workspace = true

crates/editor/src/editor.rs

@@ -1305,6 +1305,7 @@ impl Default for SelectionHistoryMode {
 ///
 /// Similarly, you might want to disable scrolling if you don't want the viewport to
 /// move.
+#[derive(Clone)]
 pub struct SelectionEffects {
     nav_history: Option<bool>,
     completions: bool,
@@ -2944,10 +2945,12 @@ impl Editor {
             }
         }
 
+        let selection_anchors = self.selections.disjoint_anchors();
+
         if self.focus_handle.is_focused(window) && self.leader_id.is_none() {
             self.buffer.update(cx, |buffer, cx| {
                 buffer.set_active_selections(
-                    &self.selections.disjoint_anchors(),
+                    &selection_anchors,
                     self.selections.line_mode,
                     self.cursor_shape,
                     cx,
@@ -2964,9 +2967,8 @@ impl Editor {
         self.select_next_state = None;
         self.select_prev_state = None;
         self.select_syntax_node_history.try_clear();
-        self.invalidate_autoclose_regions(&self.selections.disjoint_anchors(), buffer);
-        self.snippet_stack
-            .invalidate(&self.selections.disjoint_anchors(), buffer);
+        self.invalidate_autoclose_regions(&selection_anchors, buffer);
+        self.snippet_stack.invalidate(&selection_anchors, buffer);
         self.take_rename(false, window, cx);
 
         let newest_selection = self.selections.newest_anchor();
@@ -4047,7 +4049,8 @@ impl Editor {
                             // then don't insert that closing bracket again; just move the selection
                             // past the closing bracket.
                             let should_skip = selection.end == region.range.end.to_point(&snapshot)
-                                && text.as_ref() == region.pair.end.as_str();
+                                && text.as_ref() == region.pair.end.as_str()
+                                && snapshot.contains_str_at(region.range.end, text.as_ref());
                             if should_skip {
                                 let anchor = snapshot.anchor_after(selection.end);
                                 new_selections
@@ -4973,13 +4976,17 @@ impl Editor {
         })
     }
 
-    /// Remove any autoclose regions that no longer contain their selection.
+    /// Remove any autoclose regions that no longer contain their selection or have invalid anchors in ranges.
     fn invalidate_autoclose_regions(
         &mut self,
         mut selections: &[Selection<Anchor>],
         buffer: &MultiBufferSnapshot,
     ) {
         self.autoclose_regions.retain(|state| {
+            if !state.range.start.is_valid(buffer) || !state.range.end.is_valid(buffer) {
+                return false;
+            }
+
             let mut i = 0;
             while let Some(selection) = selections.get(i) {
                 if selection.end.cmp(&state.range.start, buffer).is_lt() {
@@ -5891,18 +5898,20 @@ impl Editor {
             text: new_text[common_prefix_len..].into(),
         });
 
-        self.transact(window, cx, |this, window, cx| {
+        self.transact(window, cx, |editor, window, cx| {
             if let Some(mut snippet) = snippet {
                 snippet.text = new_text.to_string();
-                this.insert_snippet(&ranges, snippet, window, cx).log_err();
+                editor
+                    .insert_snippet(&ranges, snippet, window, cx)
+                    .log_err();
             } else {
-                this.buffer.update(cx, |buffer, cx| {
+                editor.buffer.update(cx, |multi_buffer, cx| {
                     let auto_indent = match completion.insert_text_mode {
                         Some(InsertTextMode::AS_IS) => None,
-                        _ => this.autoindent_mode.clone(),
+                        _ => editor.autoindent_mode.clone(),
                     };
                     let edits = ranges.into_iter().map(|range| (range, new_text.as_str()));
-                    buffer.edit(edits, auto_indent, cx);
+                    multi_buffer.edit(edits, auto_indent, cx);
                 });
             }
             for (buffer, edits) in linked_edits {
@@ -5921,8 +5930,9 @@ impl Editor {
                 })
             }
 
-            this.refresh_inline_completion(true, false, window, cx);
+            editor.refresh_inline_completion(true, false, window, cx);
         });
+        self.invalidate_autoclose_regions(&self.selections.disjoint_anchors(), &snapshot);
 
         let show_new_completions_on_confirm = completion
             .confirm
@@ -9562,27 +9572,46 @@ impl Editor {
             // Check whether the just-entered snippet ends with an auto-closable bracket.
             if self.autoclose_regions.is_empty() {
                 let snapshot = self.buffer.read(cx).snapshot(cx);
-                for selection in &mut self.selections.all::<Point>(cx) {
+                let mut all_selections = self.selections.all::<Point>(cx);
+                for selection in &mut all_selections {
                     let selection_head = selection.head();
                     let Some(scope) = snapshot.language_scope_at(selection_head) else {
                         continue;
                     };
 
                     let mut bracket_pair = None;
-                    let next_chars = snapshot.chars_at(selection_head).collect::<String>();
-                    let prev_chars = snapshot
-                        .reversed_chars_at(selection_head)
-                        .collect::<String>();
-                    for (pair, enabled) in scope.brackets() {
-                        if enabled
-                            && pair.close
-                            && prev_chars.starts_with(pair.start.as_str())
-                            && next_chars.starts_with(pair.end.as_str())
-                        {
-                            bracket_pair = Some(pair.clone());
-                            break;
+                    let max_lookup_length = scope
+                        .brackets()
+                        .map(|(pair, _)| {
+                            pair.start
+                                .as_str()
+                                .chars()
+                                .count()
+                                .max(pair.end.as_str().chars().count())
+                        })
+                        .max();
+                    if let Some(max_lookup_length) = max_lookup_length {
+                        let next_text = snapshot
+                            .chars_at(selection_head)
+                            .take(max_lookup_length)
+                            .collect::<String>();
+                        let prev_text = snapshot
+                            .reversed_chars_at(selection_head)
+                            .take(max_lookup_length)
+                            .collect::<String>();
+
+                        for (pair, enabled) in scope.brackets() {
+                            if enabled
+                                && pair.close
+                                && prev_text.starts_with(pair.start.as_str())
+                                && next_text.starts_with(pair.end.as_str())
+                            {
+                                bracket_pair = Some(pair.clone());
+                                break;
+                            }
                         }
                     }
+
                     if let Some(pair) = bracket_pair {
                         let snapshot_settings = snapshot.language_settings_at(selection_head, cx);
                         let autoclose_enabled =

crates/editor/src/editor_tests.rs

@@ -13400,6 +13400,178 @@ async fn test_as_is_completions(cx: &mut TestAppContext) {
     cx.assert_editor_state("fn a() {}\n  unsafeˇ");
 }
 
+#[gpui::test]
+async fn test_panic_during_c_completions(cx: &mut TestAppContext) {
+    init_test(cx, |_| {});
+    let language =
+        Arc::try_unwrap(languages::language("c", tree_sitter_c::LANGUAGE.into())).unwrap();
+    let mut cx = EditorLspTestContext::new(
+        language,
+        lsp::ServerCapabilities {
+            completion_provider: Some(lsp::CompletionOptions {
+                ..lsp::CompletionOptions::default()
+            }),
+            ..lsp::ServerCapabilities::default()
+        },
+        cx,
+    )
+    .await;
+
+    cx.set_state(
+        "#ifndef BAR_H
+#define BAR_H
+
+#include <stdbool.h>
+
+int fn_branch(bool do_branch1, bool do_branch2);
+
+#endif // BAR_H
+ˇ",
+    );
+    cx.executor().run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.handle_input("#", window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.handle_input("i", window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.handle_input("n", window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.assert_editor_state(
+        "#ifndef BAR_H
+#define BAR_H
+
+#include <stdbool.h>
+
+int fn_branch(bool do_branch1, bool do_branch2);
+
+#endif // BAR_H
+#inˇ",
+    );
+
+    cx.lsp
+        .set_request_handler::<lsp::request::Completion, _, _>(move |_, _| async move {
+            Ok(Some(lsp::CompletionResponse::List(lsp::CompletionList {
+                is_incomplete: false,
+                item_defaults: None,
+                items: vec![lsp::CompletionItem {
+                    kind: Some(lsp::CompletionItemKind::SNIPPET),
+                    label_details: Some(lsp::CompletionItemLabelDetails {
+                        detail: Some("header".to_string()),
+                        description: None,
+                    }),
+                    label: " include".to_string(),
+                    text_edit: Some(lsp::CompletionTextEdit::Edit(lsp::TextEdit {
+                        range: lsp::Range {
+                            start: lsp::Position {
+                                line: 8,
+                                character: 1,
+                            },
+                            end: lsp::Position {
+                                line: 8,
+                                character: 1,
+                            },
+                        },
+                        new_text: "include \"$0\"".to_string(),
+                    })),
+                    sort_text: Some("40b67681include".to_string()),
+                    insert_text_format: Some(lsp::InsertTextFormat::SNIPPET),
+                    filter_text: Some("include".to_string()),
+                    insert_text: Some("include \"$0\"".to_string()),
+                    ..lsp::CompletionItem::default()
+                }],
+            })))
+        });
+    cx.update_editor(|editor, window, cx| {
+        editor.show_completions(&ShowCompletions { trigger: None }, window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.confirm_completion(&ConfirmCompletion::default(), window, cx)
+    });
+    cx.executor().run_until_parked();
+    cx.assert_editor_state(
+        "#ifndef BAR_H
+#define BAR_H
+
+#include <stdbool.h>
+
+int fn_branch(bool do_branch1, bool do_branch2);
+
+#endif // BAR_H
+#include \"ˇ\"",
+    );
+
+    cx.lsp
+        .set_request_handler::<lsp::request::Completion, _, _>(move |_, _| async move {
+            Ok(Some(lsp::CompletionResponse::List(lsp::CompletionList {
+                is_incomplete: true,
+                item_defaults: None,
+                items: vec![lsp::CompletionItem {
+                    kind: Some(lsp::CompletionItemKind::FILE),
+                    label: "AGL/".to_string(),
+                    text_edit: Some(lsp::CompletionTextEdit::Edit(lsp::TextEdit {
+                        range: lsp::Range {
+                            start: lsp::Position {
+                                line: 8,
+                                character: 10,
+                            },
+                            end: lsp::Position {
+                                line: 8,
+                                character: 11,
+                            },
+                        },
+                        new_text: "AGL/".to_string(),
+                    })),
+                    sort_text: Some("40b67681AGL/".to_string()),
+                    insert_text_format: Some(lsp::InsertTextFormat::PLAIN_TEXT),
+                    filter_text: Some("AGL/".to_string()),
+                    insert_text: Some("AGL/".to_string()),
+                    ..lsp::CompletionItem::default()
+                }],
+            })))
+        });
+    cx.update_editor(|editor, window, cx| {
+        editor.show_completions(&ShowCompletions { trigger: None }, window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.update_editor(|editor, window, cx| {
+        editor.confirm_completion(&ConfirmCompletion::default(), window, cx)
+    });
+    cx.executor().run_until_parked();
+    cx.assert_editor_state(
+        r##"#ifndef BAR_H
+#define BAR_H
+
+#include <stdbool.h>
+
+int fn_branch(bool do_branch1, bool do_branch2);
+
+#endif // BAR_H
+#include "AGL/ˇ"##,
+    );
+
+    cx.update_editor(|editor, window, cx| {
+        editor.handle_input("\"", window, cx);
+    });
+    cx.executor().run_until_parked();
+    cx.assert_editor_state(
+        r##"#ifndef BAR_H
+#define BAR_H
+
+#include <stdbool.h>
+
+int fn_branch(bool do_branch1, bool do_branch2);
+
+#endif // BAR_H
+#include "AGL/"ˇ"##,
+    );
+}
+
 #[gpui::test]
 async fn test_no_duplicated_completion_requests(cx: &mut TestAppContext) {
     init_test(cx, |_| {});

crates/multi_buffer/src/anchor.rs

@@ -167,10 +167,10 @@ impl Anchor {
         if *self == Anchor::min() || *self == Anchor::max() {
             true
         } else if let Some(excerpt) = snapshot.excerpt(self.excerpt_id) {
-            excerpt.contains(self)
-                && (self.text_anchor == excerpt.range.context.start
-                    || self.text_anchor == excerpt.range.context.end
-                    || self.text_anchor.is_valid(&excerpt.buffer))
+            (self.text_anchor == excerpt.range.context.start
+                || self.text_anchor == excerpt.range.context.end
+                || self.text_anchor.is_valid(&excerpt.buffer))
+                && excerpt.contains(self)
         } else {
             false
         }

crates/project/src/lsp_command.rs

@@ -2269,7 +2269,7 @@ impl LspCommand for GetCompletions {
                     // the range based on the syntax tree.
                     None => {
                         if self.position != clipped_position {
-                            log::info!("completion out of expected range");
+                            log::info!("completion out of expected range ");
                             return false;
                         }
 
@@ -2483,7 +2483,9 @@ pub(crate) fn parse_completion_text_edit(
         let start = snapshot.clip_point_utf16(range.start, Bias::Left);
         let end = snapshot.clip_point_utf16(range.end, Bias::Left);
         if start != range.start.0 || end != range.end.0 {
-            log::info!("completion out of expected range");
+            log::info!(
+                "completion out of expected range, start: {start:?}, end: {end:?}, range: {range:?}"
+            );
             return None;
         }
         snapshot.anchor_before(start)..snapshot.anchor_after(end)

crates/text/src/anchor.rs

@@ -99,7 +99,9 @@ impl Anchor {
         } else if self.buffer_id != Some(buffer.remote_id) {
             false
         } else {
-            let fragment_id = buffer.fragment_id_for_anchor(self);
+            let Some(fragment_id) = buffer.try_fragment_id_for_anchor(self) else {
+                return false;
+            };
             let mut fragment_cursor = buffer.fragments.cursor::<(Option<&Locator>, usize)>(&None);
             fragment_cursor.seek(&Some(fragment_id), Bias::Left);
             fragment_cursor

crates/text/src/text.rs

@@ -2330,10 +2330,19 @@ impl BufferSnapshot {
     }
 
     fn fragment_id_for_anchor(&self, anchor: &Anchor) -> &Locator {
+        self.try_fragment_id_for_anchor(anchor).unwrap_or_else(|| {
+            panic!(
+                "invalid anchor {:?}. buffer id: {}, version: {:?}",
+                anchor, self.remote_id, self.version,
+            )
+        })
+    }
+
+    fn try_fragment_id_for_anchor(&self, anchor: &Anchor) -> Option<&Locator> {
         if *anchor == Anchor::MIN {
-            Locator::min_ref()
+            Some(Locator::min_ref())
         } else if *anchor == Anchor::MAX {
-            Locator::max_ref()
+            Some(Locator::max_ref())
         } else {
             let anchor_key = InsertionFragmentKey {
                 timestamp: anchor.timestamp,
@@ -2354,20 +2363,12 @@ impl BufferSnapshot {
                 insertion_cursor.prev();
             }
 
-            let Some(insertion) = insertion_cursor.item().filter(|insertion| {
-                if cfg!(debug_assertions) {
-                    insertion.timestamp == anchor.timestamp
-                } else {
-                    true
-                }
-            }) else {
-                panic!(
-                    "invalid anchor {:?}. buffer id: {}, version: {:?}",
-                    anchor, self.remote_id, self.version
-                );
-            };
-
-            &insertion.fragment_id
+            insertion_cursor
+                .item()
+                .filter(|insertion| {
+                    !cfg!(debug_assertions) || insertion.timestamp == anchor.timestamp
+                })
+                .map(|insertion| &insertion.fragment_id)
         }
     }