Helps with https://github.com/zed-industries/zed/issues/38927
- **editor: Add a benchmark for find/replace**
- **text: batch fragment insertions before turning them into a SumTree**
## Context
<!-- What does this PR do, and why? How is it expected to impact users?
Not just what changed, but what motivated it and why this approach.
Link to Linear issue (e.g., ENG-123) or GitHub issue (e.g., Closes#456)
if one exists — helps with traceability. -->
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## Self-Review Checklist
<!-- Check before requesting review: -->
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- Improved performance of "Replace All" in buffer search
---------
Co-authored-by: Smit Barmase <heysmitbarmase@gmail.com>
We check `is_valid` by seeking to the first excerpt that is `>=` the
anchor, and comparing the anchor to the excerpt's start and end. But we
were missing a check for the case where seeking puts us on an excerpt
for a different buffer, for example when the anchor to be checked is
past the end of the context range for its buffer's last excerpt.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- Fixed a panic in multibuffers.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Closes #ISSUE
Release Notes:
- N/A
Previously, passing an empty range to `range_to_buffer_range` would
return no ranges, which would trigger a fallback case in the git diff
that caused the entire multibuffer to be invalidated every frame.
This PR fixes `range_to_buffer_range`, so that it returns a sensible
range if the input range is empty, preventing the fallback behaviour and
edit expansion.
Self-Review Checklist:
- [ ] I've reviewed my own diff for quality, security, and reliability
- [ ] Unsafe blocks (if any) have justifying comments
- [ ] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [ ] Performance impact has been considered and is acceptable
Closes #ISSUE
Release Notes:
- N/A or Added/Fixed/Improved ...
---------
Co-authored-by: Cole Miller <cole@zed.dev>
Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Before, every creation of `AnchorSeekTarget` called
`MultiBufferSnapshot::buffer_for_path`, which seeks the excerpts sum
tree. Now we avoid that by
- looking up the buffer snapshot for the anchor's buffer in the
`buffers` map (keyed by `BufferId`)
- handling the case where the anchor's buffer doesn't exist at the
original path key with a separate `AnchorSeekTarget::Missing` variant
We also added a separate optimization to `AnchorSeekTarget::cmp`, to
skip the full `PathKey` comparison when the cursor's `PathKeyIndex` is
the same as the anchor's. This should help with singleton multibuffers.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
---------
Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Closes#50212
There are two unreasonable coupling account for this issue, the coupling
of `use_tree_sitter` with `languge_aware` in
7892b93279/crates/editor/src/element.rs (L3820-L3822)
and the coupling of `language_aware` with `diagnostics` in
7892b93279/crates/language/src/buffer.rs (L3736-L3746)
Because of these couplings, when the editor stops using Tree-sitter
highlighting when `"semantic_tokens"` set to `"full"`, it also
accidentally stops fetching diagnostic information. This is why error
and warning underlines disappear.
I’ve fixed this by adding a separate `use_tree_sitter` parameter to
`highlighted_chunks`. This way, we can keep `language_aware` true to get
the diagnostic data we need, but still decide whether or not to apply
Tree-sitter highlights. I chose to fix this at the `highlighted_chunks`
level because I’m worried that changing the logic in the deeper layers
of the DisplayMap or Buffer might have too many side effects that are
hard to predict. This approach feels like a safer way to solve the
problem.
Release Notes:
- Fixed a bug where diagnostic underlines disappeared when
"semantic_tokens" set to "full"
---------
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
It's possible to create a multibuffer anchor that points into a specific
excerpted buffer (so not min/max), but whose main buffer `text::Anchor`
isn't contained in any of the excerpts for that buffer. When summarizing
such an anchor, we map it to the multibuffer position of the start of
the next excerpt after where the anchor "should" appear. Or at least,
that's the intention, but it turned out we had some bugs in
`summary_for_anchor` and `summaries_for_anchors` that caused them to
return bizarre summaries for these anchors. This PR fixes that and also
updates `test_random_multibuffer` to actually test
`MultiBufferSnapshot::summary_for_anchor` against a reference
implementation, including for out-of-bounds anchors.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
---------
Co-authored-by: Anthony <anthony@zed.dev>
Co-authored-by: Max <max@zed.dev>
Co-authored-by: Anthony Eid <hello@anthonyeid.me>
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
TODO:
- [x] merge main
- [x] nonshrinking `set_excerpts_for_path`
- [x] Test-drive potential problem areas in the app
- [x] prepare cloud side
- [x] test collaboration
- [ ] docstrings
- [ ] ???
## Context
### Background
Currently, a multibuffer consists of an arbitrary list of
anchor-delimited excerpts from individual buffers. Excerpt ranges for a
fixed buffer are permitted to overlap, and can appear in any order in
the multibuffer, possibly separated by excerpts from other buffers.
However, in practice all code that constructs multibuffers does so using
the APIs defined in the `path_key` submodule of the `multi_buffer` crate
(`set_excerpts_for_path` etc.) If you only use these APIs, the resulting
multibuffer will maintain the following invariants:
- All excerpts for the same buffer appear contiguously in the
multibuffer
- Excerpts for the same buffer cannot overlap
- Excerpts for the same buffer appear in order
- The placement of the excerpts for a specific buffer in the multibuffer
are determined by the `PathKey` passed to `set_excerpts_for_path`. There
is exactly one `PathKey` per buffer in the multibuffer
### Purpose of this PR
This PR changes the multibuffer so that the invariants maintained by the
`path_key` APIs *always* hold. It's no longer possible to construct a
multibuffer with overlapping excerpts, etc. The APIs that permitted
this, like `insert_excerpts_with_ids_after`, have been removed in favor
of the `path_key` suite.
The main upshot of this is that given a `text::Anchor` and a
multibuffer, it's possible to efficiently figure out the unique excerpt
that includes that anchor, if any:
```
impl MultiBufferSnapshot {
fn buffer_anchor_to_anchor(&self, anchor: text::Anchor) -> Option<multi_buffer::Anchor>;
}
```
And in the other direction, given a `multi_buffer::Anchor`, we can look
at its `text::Anchor` to locate the excerpt that contains it. That means
we don't need an `ExcerptId` to create or resolve
`multi_buffer::Anchor`, and in fact we can delete `ExcerptId` entirely,
so that excerpts no longer have any identity outside their
`Range<text::Anchor>`.
There are a large number of changes to `editor` and other downstream
crates as a result of removing `ExcerptId` and multibuffer APIs that
assumed it.
### Other changes
There are some other improvements that are not immediate consequences of
that big change, but helped make it smoother. Notably:
- The `buffer_id` field of `text::Anchor` is no longer optional.
`text::Anchor::{MIN, MAX}` have been removed in favor of
`min_for_buffer`, etc.
- `multi_buffer::Anchor` is now a three-variant enum (inlined slightly):
```
enum Anchor {
Min,
Excerpt {
text_anchor: text::Anchor,
path_key_index: PathKeyIndex,
diff_base_anchor: Option<text::Anchor>,
},
Max,
}
```
That means it's no longer possible to unconditionally access the
`text_anchor` field, which is good because most of the places that were
doing that were buggy for min/max! Instead, we have a new API that
correctly resolves min/max to the start of the first excerpt or the end
of the last excerpt:
```
impl MultiBufferSnapshot {
fn anchor_to_buffer_anchor(&self, anchor: multi_buffer::Anchor) -> Option<text::Anchor>;
}
```
- `MultiBufferExcerpt` has been removed in favor of a new
`map_excerpt_ranges` API directly on `MultiBufferSnapshot`.
## Self-Review Checklist
<!-- Check before requesting review: -->
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- N/A
---------
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Piotr Osiewicz <24362066+osiewicz@users.noreply.github.com>
Co-authored-by: Jakub Konka <kubkon@jakubkonka.com>
Co-authored-by: Conrad <conrad@zed.dev>
Previously we were iterating over all hunks across all diffs on every
frame. Now we can read off the required information as a `SumTree`
summary in constant time.
Self-Review Checklist:
- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [ ] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable
Release Notes:
- git: Fixed bad performance in large branch diffs.
When undoing a paste, it is really confusing when that actually also
removes what was type right before the paste if the paste happened fast
enough after.
Release Notes:
- Fixed undoing a paste sometimes also undoing edits right before the
paste
Update vim and helix replace to repeat based on grapheme count instead of
byte length or Unicode scalar count.
This fixes cases where a single visible character is made up of multiple
bytes or scalars, such as decomposed characters like `e\u{301}` and emoji.
Closes#51772
Release Notes:
- Fixed vim/helix's replace action to take into consideration grapheme
count
---------
Co-authored-by: dino <dinojoaocosta@gmail.com>
Many editors such as vim and emacs support "modelines", a comment at the
beginning of the file that allows the file type to be explicitly
specified along with per-file specific settings
- The amount of configurations, style and settings mapping cannot be
handled in one go, so this opens up a lot of potential improvements.
- I left out the possiblity to have "zed" specific modelines for now,
but this could be potentially interesting.
- Mapping the mode or filetype to zed language names isn't obvious
either. We may want to make it configurable.
This is my first contribution to zed, be kind. I struggled a bit to find
the right place to add those settings. I use a similar approach as done
with editorconfig (merge_with_editorconfig). There might be better ways.
Closes#4762
Release Notes:
- Add basic emacs/vim modeline support.
Supersedes #41899, changes:
- limit reading to the first and last 1kb
- add documentation
- more variables handled
- add Arc around ModelineSettings to avoid extra cloning
- changed the way mode -> language mapping is done, thanks to
`modeline_aliases` language config
- drop vim ex: support
- made "Local Variables:" handling a separate commit, so we can drop it
easily
- various code style improvements
---------
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Closes#51740
The multi-line cursor expansion operates off of byte offsets, instead of
character offsets, so multi-byte characters like the umlaut cause the
multi-line cursors to be weirdly offset. To fix we just convert the
expansion logic to rely on utf16 characters instead of bytes.
before behavior:
https://github.com/user-attachments/assets/320e24e9-0fdd-4d16-a9e8-ca17c9e21ff2
after behavior:
https://github.com/user-attachments/assets/c4f0334b-dffc-4530-91ee-577b4fab75dd
+ test to verify functionality.
Before you mark this PR as ready for review, make sure that you have:
- [x] Added a solid test coverage and/or screenshots from doing manual
testing
- [x] Done a self-review taking into account security and performance
aspects
- [x] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
Release Notes:
- editor: fixed multi-line cursor expansion dealing with multi-byte
characters.
---------
Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Closes#43329
## Summary
This fixes `path:line:column` navigation for files containing non-ASCII
text.
Before this change, open path flows were passing the external column
directly into `go_to_singleton_buffer_point`. That happened to work for
ASCII, but it was wrong for Unicode because external columns are
user-visible character positions while the editor buffer stores columns
as UTF-8 byte offsets.
This PR adds a shared text layer conversion for external row/column
coordinates and uses it in the affected open-path flows:
- file finder navigation
- recent project remote connection navigation
- recent project remote server navigation
It also adds regression coverage for the Unicode case that originally
failed.
As a small - necessary - prerequisite, this also adds
`remote_connection` test support to `file_finder`'s dev-deps so the
local regression test can build and run on this branch. That follows the
same feature mismatch pattern previously fixed in #48280. I wasn't able
to locally verify the tests/etc. w/o the addition... so I've rolled it
into this PR. Tests are green.
The earlier attempt in #47093 was headed in the right direction, but it
did not land and did not include the final regression coverage requested
in review.
## Verification
- `cargo fmt --all -- --check`
- `./script/clippy -p text`
- `./script/clippy -p file_finder`
- `./script/clippy -p recent_projects`
- `cargo test -p file_finder --lib --no-run`
- `cargo test -p file_finder
file_finder_tests::test_row_column_numbers_query_inside_file -- --exact`
- `cargo test -p file_finder
file_finder_tests::test_row_column_numbers_query_inside_unicode_file --
--exact`
- `cargo test -p text
tests::test_point_for_row_and_column_from_external_source -- --exact`
## Manual
I reproduced locally on my machine (macOS) w/ a stateless launch using a
Unicode file (Cyrillic)
Before:
- `:1:5` landed too far left
- `:1:10` landed around the 4th visible Cyrillic character
After:
- `:1:5` lands after 4 visible characters / before the 5th
- `:1:10` lands after 9 visible characters / before the 10th
Release Notes:
- Fixed `path:line:column` navigation so non-ASCII columns land on the
correct character.
---------
Co-authored-by: Kirill Bulatov <kirill@zed.dev>
BufferEvent::Edited had no way to distinguish local edits from remote
(collaboration) edits. This caused edit prediction behavior to fire on
the guest's editor when the host made document changes.
Release Notes:
- Fixed edit predictions triggering on collaboration guests when the
host edits the document.
---------
Co-authored-by: Ben Kunkle <ben@zed.dev>
This will help with test times (in some cases), as nextest cannot figure
out whether a given rdep is actually an alive edge of the build graph
Closes #ISSUE
Before you mark this PR as ready for review, make sure that you have:
- [ ] Added a solid test coverage and/or screenshots from doing manual
testing
- [ ] Done a self-review taking into account security and performance
aspects
- [ ] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
Release Notes:
- N/A
Fix a bug in the editor's handling of the
`multi_buffer::Event::ExcerptsRemoved` event, where the display map's
`folded_buffers` set was not updated according to the list of removed
buffer ids.
Since the `ProjectSearchView` now relies on the
`Editor.has_any_buffer_folded` method in order to decide the state of
the expand/collapse all excerpts button this could lead to a
bug where, after an initial project search, all excerpts would be
collapsed, and performing a new search would leave the button in a wrong
state, as all excerpts from the new search result would be expanded, but
the button would still consider that there were folded excerpts for the
buffers.
Closes#50521
Release Notes:
- Fixed bug in project search where collapsing a single buffer then
performing a new search in the same view, would break the
expand/collapse all button behavior
Paving the way to remove `ExcerptId`. Done in this PR:
- Unshipped the stack trace view
- Get rid of `push_excerpts`
- Get rid of some callers of `remove_excerpts`
We still need to remove some calls to `remove_excerpts` and other APIs,
especially in `randomly_edit_excerpts` and collaboration.
Release Notes:
- The stack trace multibuffer view has been removed.
---------
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
These tend to be very often mutated while we don't really need the
subtree sharing of TreeMaps, so replacing them here is generally
cheaper.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Co-authored by: John Tur <jtur@zed.dev>
Fixes ZED-59F
This is follow-up work from #49994; which assumed that can_resolve would
return
false for an invalid excerpt id.
Before you mark this PR as ready for review, make sure that you have:
- [ ] Added a solid test coverage and/or screenshots from doing manual
testing
- [ ] Done a self-review taking into account security and performance
aspects
- [ ] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
Release Notes:
- N/A
This PR adds a more rigorous test for the excerpt syncing logic in
`SplittableEditor`, in preparation for refactoring that code, since
we've had some bugs there.
The new test covers
- edits within the RHS multibuffer
- edits to the individual main buffers, not necessarily within the
excerpt bounds of the split diff
- excerpt expansion
- excerpt removal
- excerpt recalculation based on diff hunk ranges
Bugs fixed:
- incorrect edit merging logic in `patches_for_range`
- `merge_excerpts` leaving stale excerpt IDs in `excerpts_by_path`
Before you mark this PR as ready for review, make sure that you have:
- [x] Added a solid test coverage and/or screenshots from doing manual
testing
- [x] Done a self-review taking into account security and performance
aspects
- [ ] Aligned any UI changes with the [UI
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
Release Notes:
- N/A
For inverted diff APIs like `hunks_intersecting_base_text_range`, we
need a snapshot of the main buffer to use as context to compare hunk
anchors, convert anchors to points, etc. Previously, we were always
using a snapshot of the main buffer at the time when the diff was
calculated. This worked well for the hunks of the primary `BufferDiff`,
but it's not valid when the diff also has a secondary set of hunks,
because those hunks are recalculated on their own schedule--so it's
possible for the hunks of the secondary diff to contain anchors that are
newer than the original buffer snapshot that was taken at the time the
primary diff hunks were last calculated. This caused a panic when using
these anchors with the original buffer snapshot.
This PR fixes the issue by using the same approach for inverted diffs as
for non-inverted diffs at the multibuffer level: we take a snapshot of
the main buffer at the time when we snapshot the diff state (including
the diff itself), guaranteeing that that snapshot will be new enough to
resolve all the anchors included in both the primary diff and the
secondary diff.
Closes ZED-54J
Release Notes:
- Fixed a panic that could occur when using the branch diff in split
view mode.
---------
Co-authored-by: Antonio Scandurra <me@as-cii.com>
This reverts commit 1d66bbe06f.
Needs 2 more fixes:
* enter does not move to the first excerpt anymore
* there could be situations when a narrowed search does not decrease the
excerpt enough to see the result onscreen
Release Notes:
- N/A
- Reduce some re-allocations in `text_anchors_to_visible_anchors` and
`refresh_semantic_tokens`
- Process `raw_to_buffer_semantic_tokens` work on the background thread
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Seems that `SmallVec::clone` is pretty expensive in a generic case, and
specialising it improves the performance quite a bit!
Release Notes:
- Improved performance of different building blocks within the
MultiBuffer.
---------
Co-authored-by: Lukas Wirth <lukas@zed.dev>
Replaces a bunch of `impl FnMut` parameters with `&mut dyn FnMut` for
functions where this is the sole generic parameter.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
Currently, the next chunk is generated by traversing all characters of
the current folded chunk until a tab is found. Since we already have
bitmasks for characters and tabs, we can also propagate the newlines
bitmap from the rope and use it to make this computation O(1) in all
cases.
I haven’t run benchmarks yet.
Release Notes:
- N/A
- Defer syncing block maps from `set_companion`, eliminating some
redundant recomputations
- Emit one large multibuffer edit from `set_show_deleted_hunks` instead
of many small edits, to avoid bad case for block map
This cuts hangs roughly in half when toggling between views in a large
diff (1000 commits from the chromium repository).
<!-- Before you mark this PR as ready for review, make sure that you
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-->
Release Notes:
- Improved performance with large diffs when toggling between diff
views.
---------
Co-authored-by: Jakub Konka <kubkon@jakubkonka.com>
Co-authored-by: Lukas Wirth <lukas@zed.dev>
Our strategy for keeping excerpts in sync between the two sides of the
split diff is generally
- mutate the excerpts on the RHS
- pull out the new excerpts for the affected path from the RHS
- translate those ranges to the LHS
- update the LHS excerpts with those ranges
But this can break down when the translated ranges overlap on the LHS
despite the original ranges not overlapping on the RHS. This can happen,
for example, when a large deletion in a file crosses several excerpt
boundaries. It's rare because normally excerpt boundaries in the project
diff and branch diff are adjusted to keep entire diff hunks in view, but
we defer this for dirty files, so it's not hard to trigger it when using
the agent or editing an individual file while the diff is open in
another tab.
Release Notes:
- Fixed a panic that could occur when editing files while the project
diff or branch diff was open.
---------
Co-authored-by: Zed Zippy <234243425+zed-zippy[bot]@users.noreply.github.com>
Second attempt at fixing
https://github.com/zed-industries/zed/pull/49047, this also removes some
of the sorting hacks as they should ideally not be necessary anymore
after this fix
Release Notes:
- N/A *or* Added/Fixed/Improved ...
## Bug
**Sentry:**
[ZED-3W3](https://sentry.io/organizations/zed-dev/issues/7085300207/)
(13 events, first seen 2025-12-03)
`summaries_for_anchors` panics with "cannot seek backward" when
iterating selection anchors whose excerpt locators are no longer in
ascending order after an `update_path_excerpts` call.
### Root cause
`update_path_excerpts` merges new excerpt ranges with existing ones.
When an existing excerpt has no overlap with any new range (e.g.
`existing_range.end < new.context.start`), it is removed from the
excerpts tree but is **not** recorded in `replaced_excerpts`. Its stale
locator persists in the `excerpt_ids` tree.
Later, when a new excerpt is inserted for a different path whose locator
falls between the stale locator and another surviving excerpt,
`summaries_for_anchors` can encounter anchors in an order where it needs
to seek the cursor *backward* — violating the forward-only cursor
invariant.
Concretely, the scenario requires:
1. A path with ≥3 excerpts (E_B1, E_B2, E_B3) with anchors in E_B2 and
E_B3.
2. An `update_path_excerpts` call that keeps E_B1, **removes E_B2** (no
overlap → no `replaced_excerpts` entry), and replaces E_B3 with a new
excerpt N.
3. A new path D inserted between paths B and C, whose excerpt E_D gets a
locator between N and E_B2's stale locator.
4. Resolving the old anchors: E_B2's stale locator seeks past E_D, then
E_B3→N tries to seek backward to N — **panic**.
## Fix
In the two branches of `update_path_excerpts` where existing excerpts
are removed without being absorbed into a new range, map the removed
excerpt to the nearest surviving neighbor (the last kept or inserted
excerpt) in `replaced_excerpts`. This ensures stale anchors always remap
to a valid, correctly-ordered locator.
The two branches are:
- `existing_range.end < new.context.start` — existing excerpt falls
entirely before the next new range
- `(None, Some(...))` — no more new ranges for remaining existing
excerpts
## Verification
- A reproduction test
(`test_cannot_seek_backward_after_excerpt_replacement`) that constructs
the exact crash scenario now passes.
- Full `multi_buffer` test suite (48 tests) passes with no regressions.
- Clippy is clean.
Release Notes:
- Fixed a possible crash when updating excerpts in multibuffers
These are heavily used by the side-by-side diff. Previously, we were
iterating over all hunks for each call. Now we skip hunks that can't
affect the provided range.
Release Notes:
- N/A
When the version is the same we used to still seek through the
underlying fragment sumtree despite having nothing to return. This has a
lot of unnecessary overhead.
Release Notes:
- N/A *or* Added/Fixed/Improved ...
