editor: Fix incorrect offset passed to acp completion provider (#38321)

Might fix | ZED-15G
Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/agent_ui/src/context_picker/completion_provider.rs

@@ -743,15 +743,15 @@ impl CompletionProvider for ContextPickerCompletionProvider {
         _window: &mut Window,
         cx: &mut Context<Editor>,
     ) -> Task<Result<Vec<CompletionResponse>>> {
-        let state = buffer.update(cx, |buffer, _cx| {
-            let position = buffer_position.to_point(buffer);
-            let line_start = Point::new(position.row, 0);
-            let offset_to_line = buffer.point_to_offset(line_start);
-            let mut lines = buffer.text_for_range(line_start..position).lines();
-            let line = lines.next()?;
-            MentionCompletion::try_parse(line, offset_to_line)
-        });
-        let Some(state) = state else {
+        let snapshot = buffer.read(cx).snapshot();
+        let position = buffer_position.to_point(&snapshot);
+        let line_start = Point::new(position.row, 0);
+        let offset_to_line = snapshot.point_to_offset(line_start);
+        let mut lines = snapshot.text_for_range(line_start..position).lines();
+        let Some(line) = lines.next() else {
+            return Task::ready(Ok(Vec::new()));
+        };
+        let Some(state) = MentionCompletion::try_parse(line, offset_to_line) else {
             return Task::ready(Ok(Vec::new()));
         };
 
@@ -761,7 +761,6 @@ impl CompletionProvider for ContextPickerCompletionProvider {
             return Task::ready(Ok(Vec::new()));
         };
 
-        let snapshot = buffer.read(cx).snapshot();
         let source_range = snapshot.anchor_before(state.source_range.start)
             ..snapshot.anchor_after(state.source_range.end);
 

crates/editor/src/editor.rs

@@ -5473,16 +5473,18 @@ impl Editor {
         if position.diff_base_anchor.is_some() {
             return;
         }
-        let (buffer, buffer_position) =
-            if let Some(output) = self.buffer.read(cx).text_anchor_for_position(position, cx) {
-                output
-            } else {
-                return;
-            };
+        let buffer_position = multibuffer_snapshot.anchor_before(position);
+        let Some(buffer) = buffer_position
+            .buffer_id
+            .and_then(|buffer_id| self.buffer.read(cx).buffer(buffer_id))
+        else {
+            return;
+        };
         let buffer_snapshot = buffer.read(cx).snapshot();
 
         let query: Option<Arc<String>> =
-            Self::completion_query(&multibuffer_snapshot, position).map(|query| query.into());
+            Self::completion_query(&multibuffer_snapshot, buffer_position)
+                .map(|query| query.into());
 
         drop(multibuffer_snapshot);
 
@@ -5568,6 +5570,11 @@ impl Editor {
             }
         };
 
+        let Anchor {
+            excerpt_id: buffer_excerpt_id,
+            text_anchor: buffer_position,
+            ..
+        } = buffer_position;
         let (word_replace_range, word_to_exclude) = if let (word_range, Some(CharKind::Word)) =
             buffer_snapshot.surrounding_word(buffer_position, false)
         {
@@ -5623,7 +5630,7 @@ impl Editor {
         let (mut words, provider_responses) = match &provider {
             Some(provider) => {
                 let provider_responses = provider.completions(
-                    position.excerpt_id,
+                    buffer_excerpt_id,
                     &buffer,
                     buffer_position,
                     completion_context,

crates/text/src/text.rs

@@ -3078,7 +3078,7 @@ impl ToOffset for usize {
     fn to_offset(&self, snapshot: &BufferSnapshot) -> usize {
         assert!(
             *self <= snapshot.len(),
-            "offset {} is out of range, max allowed is {}",
+            "offset {} is out of range, snapshot length is {}",
             self,
             snapshot.len()
         );