fix(pull): handle empty pull request files view to allow reviews

[eliroca]

Example: https://gitea.com/eliroca/empty-pull-request/pulls/1

And the "Files Changed" tab: https://gitea.com/eliroca/empty-pull-request/pulls/1/files

after commit not found in PR commits

Instead, let's handle empty pull requests and show the usual UI.

[bircni]

Why should we handle empty pull requests?
there is nothing to review we should the just show a better error

[wxiaoguang]

Thank you for the fix, will do some fine tunes.

[eliroca]

Why should we handle empty pull requests? there is nothing to review we should the just show a better error

A use-case is to use an empty PR as placeholder to trigger early reviews for a new branch.

[wxiaoguang]

Made some changes:

1. clarify the "commits list" range (added some comments)
2. use 404 page instead of plain HTTP error
3. make "beforeCommit" use the same logic as "afterCommit" (less "if", easier to read)
4. merge the tests (save CI time)
5. make test code explicitly assert the expected string, otherwise assert.Equal(t, 0 and assert.False( can succeed on almost every page.

[eliroca]

A PR also becomes empty after the changes get manually merged, outside of the PR.

[wxiaoguang]

A PR also becomes empty after the changes get manually merged, outside of the PR.

I can see 2 different cases:

1. the "head" and "base" commits are the same one, then no "commit list"
2. the "head" and "base" are different, there are commits between them, but the diff is empty

And IIRC there are also some bugs reports for these edge cases, so maybe it needs more refactoring work in the future.

(yes, not in this PR's scope 😄 )

[Copilot]

Pull request overview

This PR fixes the “Files Changed” view for empty pull requests (where the compare commit list can be empty because merge-base == head), so the page renders normally instead of erroring out, enabling users to submit PR reviews even when there are no file changes.

Changes:

• Adjusts viewPullFiles commit resolution to gracefully handle empty PRs by falling back to loading HeadCommitID / CompareBase directly from the git repo when they are not present in the PR commit list.
• Replaces the previous “commit not found in PR commits” 400 behavior with a NotFound response for invalid commit selections.
• Adds an integration test asserting that the PR “Files” tab renders and shows the “Diff Content Not Available” placeholder for an empty PR.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
routers/web/repo/pull.go	Makes the pull files view resilient to empty PR commit lists by fetching missing base/head commits from the repo.
tests/integration/pull_status_test.go	Adds coverage to ensure empty PRs can load the /files tab and display the expected placeholder content.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[wxiaoguang]

@eliroca does the new change look good to you?

ps: do you need the changes to be backported to 1.26? If yes, it needs to manually backport because the the main branch code changed a lot after PRs like Refactor pull request view (1) (#37380), so simple cherry-pick doesn't work.

---

Update: thanks to bircni , backport here: #37785

[eliroca]

@wxiaoguang: with this change, on repos with unrelated git histories, looking at the PR throws:

500 Internal Server Error
An error occurred:

GetCompareInfo, MergeBase: get merge-base of 7f5ea225bc4ee889b16bc5f7b4df104f6fa86b573952e58d3aaa8ded73770317 and 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837 failed: exit status 1 - 

I specifically tested that, as I've split the changes in this PR from a commit tackling both: empty PRs and unrelated histories diff: eliroca@a12e6e0

Example PR with unrelated histories, no diff is shown: https://gitea.com/eliroca/freetype2/pulls/1

logs here

Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:gitcmd.(*Command).StartWithStderr, repo:.../eroca/freetype2.git): /usr/bin/git cat-file --batch-command
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:git.(*Repository).hashObjectBytes, repo:.../eroca/freetype2.git): /usr/bin/git hash-object --stdin
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:repo.GetMergedBaseCommitID, repo:.../eroca/freetype2.git): /usr/bin/git rev-list -1 --skip=1 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:gitrepo.GetDiffShortStatByCmdArgs, repo:.../eroca/freetype2.git): /usr/bin/git diff --shortstat 381934cb51593257d5a27e88fd85438aa9c75b255c1d21d0fdc9441a4e462430 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 services/pull/pull.go:815:GetSquashMergeCommitMessages() [E] Unable to get merge base commit:  Error: object does not exist [id: , rel_path: ]
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:git.GetFullCommitID, repo:.../eroca/freetype2.git): /usr/bin/git rev-parse refs/heads/slfo-1.2
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:git.GetFullCommitID, repo:.../eroca/freetype2.git): /usr/bin/git rev-parse refs/pull/3/head
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../git/gitcmd/command.go:422:(*Command).Start() [D] git.Command: git.Run(by:gitrepo.MergeBase, repo:.../eroca/freetype2.git): /usr/bin/git merge-base -- 7f5ea225bc4ee889b16bc5f7b4df104f6fa86b573952e58d3aaa8ded73770317 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 routers/web/repo/pull.go:595:prepareViewPullInfo() [E] GetCompareInfo: MergeBase: get merge-base of 7f5ea225bc4ee889b16bc5f7b4df104f6fa86b573952e58d3aaa8ded73770317 and 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837 failed: exit status 1 -
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 .../context/context_response.go:82:(*Context).HTML() [D] Template: status/500
Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 HTTPRequest [I] router: completed GET /eroca/freetype2/pulls/3 for <IP>:55428, 500 Internal Server Error in 100.4ms @ repo/issue_view.go:317(repo.ViewIssue)

[wxiaoguang]

@wxiaoguang: with this change, on repos with unrelated git histories, looking at the PR throws:

IIRC the "unrelated git histories" problems should have been fixed by Fix compare dropdown for branches without common history (#37470)

Is there a change in this PR related to "unrelated git histories"?

[wxiaoguang]

Mai 19 19:25:05 gitea.local gitea[10554]: 2026/05/19 19:25:05 routers/web/repo/pull.go:595:prepareViewPullInfo() [E] GetCompareInfo: MergeBase: get merge-base of 7f5ea225bc4ee889b16bc5f7b4df104f6fa86b573952e58d3aaa8ded73770317 and 255e20faae919f1559f9c831d073036810dc7c7aec38c98ff0efea0240430837 failed: exit status 1 -

And there is no "routers/web/repo/pull.go:595:prepareViewPullInfo() " on main branch

[eliroca]

I was testing with 1.26.1, sorry for the noise if this is meanwhile fixed in main.

[wxiaoguang]

I was testing with 1.26.1, sorry for the noise if this is meanwhile fixed in main.

1.26 branch also has the fix : #37472. (also thanks to @bircni)

[bircni]

So merge?

[eliroca]

Can you please verify that the changes don't break PRs with unrelated histories as in my test?

[wxiaoguang]

Can you please verify that the changes don't break PRs with unrelated histories as in my test?

Not quite sure about what you are referring to.

The changes made by me:

• 8dd0517 : it is the same logic as yours (refactor the test to a more stable approach)
• 7350a67 : merge the tests (your test logic is still kept)
• e500b56 : it only added a comment FIXME

---

If you'd like to improve, feel free to make more improvements and/or add more tests.

[eliroca]

It is not related to the changes here, my assumption was wrong. Please proceed here, I'll continue with a test for unrelated histories PRs tomorrow, and will follow up with a PR possibly. Sorry again for the noise.