forgejo/services/gitdiff
Mathieu Fenniak 7f6b9a8867 fix: expanding exactly 20 lines between diff sections leaves visual artifact (#8519)
Fixes #8488.

The issue was caused by having exactly 20 lines of text between two diff sections, which is `BlobExcerptChunkSize`.  The previous diff section ends at 530, the next diff section starts at 551, leaving 20 hidden lines.  This triggered an off-by-one error in determining whether a synthetic section should be added to the render to include a new expander; it was falsely being triggered when it shouldn't have been.

Mostly correct logic was already present in `GetExpandDirection`, so I changed the `ExcerptBlob` web rendering to use `GetExpandDirection` on whether to include the synthetic section.  Then I covered `GetExpandDirection` with unit tests covering all boundary conditions, which discovered one other minor bug -- the case where exactly `BlobExcerptChunkSize` is hidden between two diff sections should never have displayed an "Up" and "Down" expansion, but just a single expander (as below).

![Untitled-2025-07-04-1538(1)](/attachments/05573c5e-3cd4-46d5-8c1f-ecdb28302a19)

Note that *technically* the `ExcerptBlob` change is not covered by any new tests... but the relevant logic has been moved to somewhere more easily testable and fully covered.  If this isn't covered enough for tests, let me know.

## Checklist

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### Tests

- I added test coverage for Go changes...
  - [x] in their respective `*_test.go` for unit tests.
  - [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [ ] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.

### Release notes

- [ ] I do not want this change to show in the release notes.
- [x] I want the title to show in the release notes with a link to this pull request.
- [ ] I want the content of the `release-notes/<pull request number>.md` to be be used for the release notes instead of the title.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/8519
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Mathieu Fenniak <mathieu@fenniak.net>
Co-committed-by: Mathieu Fenniak <mathieu@fenniak.net>
2025-07-16 08:04:38 +02:00
..
testdata/academic-module rm .sample hooks which aren't used (#19101) 2022-03-16 10:33:07 +00:00
csv.go Use Go 1.21 and update dependencies (#26878) 2023-09-03 10:34:57 +00:00
csv_test.go chore: branding import path (#7337) 2025-03-27 19:40:14 +00:00
gitdiff.go fix: expanding exactly 20 lines between diff sections leaves visual artifact (#8519) 2025-07-16 08:04:38 +02:00
gitdiff_test.go fix: expanding exactly 20 lines between diff sections leaves visual artifact (#8519) 2025-07-16 08:04:38 +02:00
highlightdiff.go Update module github.com/golangci/golangci-lint/cmd/golangci-lint to v2 (forgejo) (#7367) 2025-03-28 22:22:21 +00:00
highlightdiff_test.go Update module github.com/golangci/golangci-lint/cmd/golangci-lint to v2 (forgejo) (#7367) 2025-03-28 22:22:21 +00:00
main_test.go chore: branding import path (#7337) 2025-03-27 19:40:14 +00:00