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edit prediction: Fix crash in highlight_text (#23766)
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This fixes the panics we we're seeing in `EditPreview::highlight_edits`.
The reason for this was that we were interpolating edits incorrectly.

Here's an example:

```rust
let a = 0; // existing code
let c = 2; // suggested by edit prediction
```
The edits would look like this: `[(Point(1, 0)..Point(1, 0), "let c =
2;"]`

Now i type:
```rust
let a = 0; // existing code
let b = 1; // added this line
let c = 2; // suggested by edit prediction
```

Before this change, the `interpolate` function would allow insertions
before the edit prediction edits, the anchors will move to the next
line.
The edits would look now like this: `[(Point(2, 0)..Point(2, 0), "let c
= 2;"]`

However, now we end up with a call to `EditPreview::highlight_edits`,
with the following parameters:
- current_snapshot: 
  ```rust
  let a = 0;
  let b = 1;
  ```
- edits: `[(Point(2, 0)..Point(2, 0), "let c = 2;"]`
- applied_edits_snapshot:
  ```rust
  let a = 0;
  let c = 2;
  ```

And here you can see the issue, applying the `edits` to the
`current_snapshot` should always end up re-creating the text that is
present in the `applied_edits_snapshot`. That is not the case here
though, meaning that the offsets in the new buffer are not correct,
which can either lead to a confusing popup or a crash if the suggestion
is at the end of the file.

Here's a real world example (edit prediction is ONLY suggesting to
delete a new line):

<img width="487" alt="Screenshot 2025-01-27 at 13 05 26"
src="https://github.com/user-attachments/assets/a0a8064e-8cfa-48b2-9f1c-efc2d0d9d7d4"
/>

We fixed this by only allowing interpolation if the user is editing
after all the edit predictions OR if the user edit is a subset of the
model suggestion.



Co-Authored-by: Antonio <antonio@zed.dev>

Release Notes:

- N/A

Co-authored-by: Antonio <antonio@zed.dev>
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@bennetbo @as-cii
bennetbo and as-cii authored Jan 28, 2025
1 parent b99159c commit dfed43a
Showing 1 changed file with 42 additions and 61 deletions.
103 changes: 42 additions & 61 deletions crates/zeta/src/zeta.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -103,23 +103,23 @@ fn interpolate(
) -> Option<Vec<(Range<Anchor>, String)>> {
let mut edits = Vec::new();

let mut user_edits = new_snapshot
.edits_since::<usize>(&old_snapshot.version)
.peekable();
for (model_old_range, model_new_text) in current_edits.iter() {
let model_offset_range = model_old_range.to_offset(old_snapshot);
while let Some(next_user_edit) = user_edits.peek() {
if next_user_edit.old.end < model_offset_range.start {
user_edits.next();
let mut model_edits = current_edits.into_iter().peekable();
for user_edit in new_snapshot.edits_since::<usize>(&old_snapshot.version) {
while let Some((model_old_range, _)) = model_edits.peek() {
let model_old_range = model_old_range.to_offset(old_snapshot);
if !model_old_range.is_empty() {
return None;
} else if model_old_range.end < user_edit.old.start {
let (model_old_range, model_new_text) = model_edits.next().unwrap();
edits.push((model_old_range.clone(), model_new_text.clone()));
} else {
break;
}
}

if let Some(user_edit) = user_edits.peek() {
if user_edit.old.start > model_offset_range.end {
edits.push((model_old_range.clone(), model_new_text.clone()));
} else if user_edit.old == model_offset_range {
if let Some((model_old_range, model_new_text)) = model_edits.peek() {
let model_old_offset_range = model_old_range.to_offset(old_snapshot);
if user_edit.old == model_old_offset_range {
let user_new_text = new_snapshot
.text_for_range(user_edit.new.clone())
.collect::<String>();
Expand All @@ -128,20 +128,26 @@ fn interpolate(
if !model_suffix.is_empty() {
edits.push((
new_snapshot.anchor_after(user_edit.new.end)
..new_snapshot.anchor_before(user_edit.new.end),
model_suffix.into(),
..new_snapshot.anchor_after(user_edit.new.end),
model_suffix.to_string(),
));
}

user_edits.next();
} else {
return None;
model_edits.next();
continue;
}
} else {
return None;
}
} else {
}

return None;
}

for (model_old_range, model_new_text) in model_edits {
let model_old_offset_range = model_old_range.to_offset(old_snapshot);
if model_old_offset_range.is_empty() {
edits.push((model_old_range.clone(), model_new_text.clone()));
} else {
return None;
}
}

Expand Down Expand Up @@ -1277,10 +1283,10 @@ mod tests {

#[gpui::test]
async fn test_inline_completion_basic_interpolation(cx: &mut TestAppContext) {
let buffer = cx.new(|cx| Buffer::local("Lorem ipsum dolor", cx));
let buffer = cx.new(|cx| Buffer::local("Lo ips dolor", cx));
let edits: Arc<[(Range<Anchor>, String)]> = cx.update(|cx| {
to_completion_edits(
[(2..5, "REM".to_string()), (9..11, "".to_string())],
[(2..2, "REM".to_string()), (6..6, "UM".to_string())],
&buffer,
cx,
)
Expand Down Expand Up @@ -1314,80 +1320,55 @@ mod tests {
&buffer,
cx
),
vec![(2..5, "REM".to_string()), (9..11, "".to_string())]
vec![(2..2, "REM".to_string()), (6..6, "UM".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(2..5, "")], None, cx));
buffer.update(cx, |buffer, cx| buffer.edit([(2..2, "R")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(2..2, "REM".to_string()), (6..8, "".to_string())]
vec![(3..3, "EM".to_string()), (7..7, "UM".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.undo(cx));
buffer.update(cx, |buffer, cx| buffer.edit([(7..7, "U")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(2..5, "REM".to_string()), (9..11, "".to_string())]
vec![(3..3, "EM".to_string()), (8..8, "M".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(2..5, "R")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(3..3, "EM".to_string()), (7..9, "".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(3..3, "E")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(4..4, "M".to_string()), (8..10, "".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(4..4, "M")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(9..11, "".to_string())]
);
// Editing after all the model edits should always keep the inline completion
buffer.update(cx, |buffer, cx| buffer.edit([(10..10, "X")], None, cx));
assert_eq!(completion.interpolate(&buffer.read(cx).snapshot()), None);

buffer.update(cx, |buffer, cx| buffer.edit([(4..5, "")], None, cx));
buffer.update(cx, |buffer, cx| buffer.undo(cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(4..4, "M".to_string()), (8..10, "".to_string())]
vec![(3..3, "EM".to_string()), (8..8, "M".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(8..10, "")], None, cx));
buffer.update(cx, |buffer, cx| buffer.edit([(8..8, "M")], None, cx));
assert_eq!(
from_completion_edits(
&completion.interpolate(&buffer.read(cx).snapshot()).unwrap(),
&buffer,
cx
),
vec![(4..4, "M".to_string())]
vec![(3..3, "EM".to_string())]
);

buffer.update(cx, |buffer, cx| buffer.edit([(4..6, "")], None, cx));
// Editing before the model edits should always remove the inline completion
buffer.update(cx, |buffer, cx| buffer.edit([(0..0, "I")], None, cx));
assert_eq!(completion.interpolate(&buffer.read(cx).snapshot()), None);
})
}
Expand Down

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