[bug] GitHub api request fails when PR diff is > 300 files

[ilynehan]

Report

What did you do?

We are running a custom danger file on PR diff:

bundle exec danger --dangerfile=danger/DangerCheckDiff.rb --danger_id=check_diff --fail-on-errors=true

We have started to see failures on CI within the last month or so when running this for PRs that have more than 300 files diff.

Here's the error log:

GET https://api.github.com/repos/procore/android/pulls/18757: 406 - Sorry, the diff exceeded the maximum number of files (300). Consider using 'List pull requests files' API or locally cloning the repository instead. (Octokit::NotAcceptable)
Error summary:
  resource: PullRequest
  field: diff
  code: too_large // See: https://docs.github.com/rest/pulls/pulls#list-pull-requests-files

What did you expect to happen?

Danger runs successfully on PRs with diff of over 300 files.

What happened instead?

Danger fails with error (see above)

Your Environment

• Which CI are you running on? - CircleCI

• Are you running the latest version of Danger? - Yes, we are on danger 9.4.3

• What is your Dangerfile?

  # we are checking all our modified & added files
  (git.modified_files + git.added_files).each do |file|
    ...

[orta]

This is how we solved it in danger js, for anyone interested in making a PR: danger/danger-js#1440

[technicalpickles]

Did some poking around to see where this change would need to be, and think I narrowed it down to here:

danger/lib/danger/request_sources/github/github.rb

Lines 79 to 81 in b5e62e8

	def pr_diff
	@pr_diff ||= client.pull_request(ci_source.repo_slug, ci_source.pull_request_id, accept: "application/vnd.github.v3.diff")
	end