[mvanhorn]

Description

When a pull request's head fork has been deleted, GitHub returns head.repo as null, and GHCommitPointer.getCommit() threw a NullPointerException because it called getRepository().getCommit(getSha()).

The head commit is still reachable in the base repository, since GitHub keeps pull request commits there. GHPullRequest.getHead() and getBase() now link each pointer back to its pull request, and getCommit() looks the SHA up in the pull request's repository when the pointer has none. getRepository() still returns null in that case, and its javadoc says so. An IOException is left only for a pointer with neither a repository nor a pull request.

GHCommitPointerTest.getCommitFromDeletedHeadRepository replays a snapshot of checkstyle/checkstyle#1, the example from the issue, and checks that the head repository is null and that getCommit() returns 4889a777. GHCommitPointerTest, GHPullRequestTest, GHEventPayloadTest and ArchTests pass, and spotless:check and clean install -DskipTests pass.

Fixes #2035

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[rnveach]

This looks like an exact duplicate of #2265 and I commented at #2265 (comment) that this wasn't a fix. It just replaces NPE with IOE.

[mvanhorn]

@rnveach You're right. The first version only swapped the NPE for an IOException, which is the same thing #2265 did. I've reworked it in 90e9ae6 so getCommit() actually returns the commit.

When a fork is deleted, GitHub sends head.repo as null. The head commit is still in the base repository, though, because GitHub keeps PR commits there (refs/pull/N/head). For checkstyle/checkstyle#1, GET /repos/checkstyle/checkstyle/commits/4889a777... returns the head commit.

So now GHPullRequest.getHead() and getBase() link each pointer back to its pull request. When the pointer has no repository, GHCommitPointer.getCommit() looks the SHA up in the pull request's repository. getRepository() still returns null in that case, because the fork really is gone. The javadoc now says so. The IOException is only left for a pointer that has no repository and no pull request either, such as one built by hand.

The new test is a WireMock snapshot of checkstyle/checkstyle#1, your example from the issue. It checks that getHead().getRepository() is null and that getHead().getCommit() returns 4889a777 from checkstyle/checkstyle.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.45%. Comparing base (f351e37) to head (9ce33d1).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2340      +/-   ##
============================================
+ Coverage     85.41%   85.45%   +0.03%     
- Complexity     2568     2576       +8     
============================================
  Files           242      242              
  Lines          7577     7584       +7     
  Branches        399      401       +2     
============================================
+ Hits           6472     6481       +9     
+ Misses          869      867       -2     
  Partials        236      236              

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[mvanhorn]

Added tests in 9ce33d1 for the three partial branches Codecov flagged: a base-pointer getCommit() case that resolves through the base repository, and a pull request whose head and base are unset. Production code is unchanged. mvn -Dtest=GHCommitPointerTest test and mvn spotless:check pass locally.