Auto-merge fails when GitHub checks required for merge

[tpolekhin]

Community Note

• Please vote on this issue by adding a 👍 reaction to the original issue to help the community and maintainers prioritize this request. Searching for pre-existing feature requests helps us consolidate datapoints for identical requirements into a single place, thank you!
• Please do not leave "+1" or other comments that do not add relevant new information or questions, they generate extra noise for issue followers and do not help prioritize the request.
• If you are interested in working on this issue or have submitted a pull request, please leave a comment.

---

Overview of the Issue

Atlantis auto merge after apply fails when GitHub repo is configured to require atlantis/apply check to pass before allowing merge. Seems like a race condition when Atlantis tries to merge PR before GitHub realises that atlantis/apply check has passed and unblocks merge.

Reproduction Steps

1. Enable auto merge in Atlantis server config ATLANTIS_AUTOMERGE=true
2. Set apply_requirements: [approved, undiverged] in server side config
3. Set GitHub branch protection rules to require atlantis/apply check to pass before allowing merge

5. Run standard Atlantis workflow for pull request

Logs

Logs

{"level":"info","ts":"2023-03-15T13:04:45.139Z","caller":"events/events_controller.go:545","msg":"parsed comment as command=\"apply\" verbose=false dir=\"\" workspace=\"\" project=\"\" flags=\"\"","json":{"gh-request-id":"X-Github-Delivery=f4627360-c331-11ed-840a-b249a2a93464"}}
{"level":"info","ts":"2023-03-15T13:04:47.272Z","caller":"terraform/terraform_client.go:361","msg":"Detected module requires version: 1.4.0","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"info","ts":"2023-03-15T13:04:47.538Z","caller":"runtime/apply_step_runner.go:39","msg":"starting apply","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"info","ts":"2023-03-15T13:04:53.582Z","caller":"models/shell_command_runner.go:156","msg":"successfully ran \"/home/atlantis/.atlantis/bin/terraform1.4.0 apply -input=false \\\"/home/atlantis/.atlantis/repos/<redacted>/terraform-infrastructure/6/default/<redacted>/<redacted>-default.tfplan\\\"\" in \"/home/atlantis/.atlantis/repos/<redacted>/terraform-infrastructure/6/default/<redacted>\"","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"info","ts":"2023-03-15T13:04:53.582Z","caller":"runtime/apply_step_runner.go:58","msg":"apply successful, deleting planfile","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"info","ts":"2023-03-15T13:04:53.832Z","caller":"events/instrumented_project_command_runner.go:87","msg":"apply success. output available at: https://github.com/<redacted>/terraform-infrastructure/pull/6","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"info","ts":"2023-03-15T13:04:56.578Z","caller":"events/automerger.go:32","msg":"automerging pull request","json":{"repo":"<redacted>/terraform-infrastructure","pull":"6"}}
{"level":"error","ts":"2023-03-15T13:04:57.450Z","caller":"vcs/instrumented_client.go:231","msg":"Unable to merge pull, error: merging pull request: PUT https://api.github.com/repos/<redacted>/terraform-infrastructure/pulls/6/merge: 405 This branch must not contain merge commits. []","json":{"pull-num":6},"stacktrace":"github.com/runatlantis/atlantis/server/events/vcs.(*InstrumentedClient).MergePull\n\tgithub.com/runatlantis/atlantis/server/events/vcs/instrumented_client.go:231\ngithub.com/runatlantis/atlantis/server/events/vcs.(*ClientProxy).MergePull\n\tgithub.com/runatlantis/atlantis/server/events/vcs/proxy.go:84\ngithub.com/runatlantis/atlantis/server/events.(*AutoMerger).automerge\n\tgithub.com/runatlantis/atlantis/server/events/automerger.go:35\ngithub.com/runatlantis/atlantis/server/events.(*ApplyCommandRunner).Run\n\tgithub.com/runatlantis/atlantis/server/events/apply_command_runner.go:183\ngithub.com/runatlantis/atlantis/server/events.(*DefaultCommandRunner).RunCommentCommand\n\tgithub.com/runatlantis/atlantis/server/events/command_runner.go:296"}

Environment details

• Atlantis version: v0.23.2
• Deployment method: GCE tf module
• Atlantis flags:

  env_vars = {
    GOOGLE_IMPERSONATE_SERVICE_ACCOUNT = var.impersonate_service_account
    ATLANTIS_AUTOMERGE                 = true
    ATLANTIS_WRITE_GIT_CREDS           = true
    ATLANTIS_REPO_ALLOWLIST            = "github.com/<redacted>/terraform-infrastructure"
    ATLANTIS_ATLANTIS_URL              = "https://${var.domain}"
    ATLANTIS_REPO_CONFIG_JSON          = jsonencode(yamldecode(file("${path.module}/server-atlantis.yaml")))
  }

• Atlantis server-side config file:

repos:
  - id: github.com/<redacted>/terraform-infrastructure
    branch: /^main$/
    plan_requirements: [undiverged]
    apply_requirements: [approved, undiverged]
    import_requirements: [approved, mergeable, undiverged]
    allow_custom_workflows: false
    delete_source_branch_on_merge: true

• Repo atlantis.yaml file:

version: 3
parallel_plan: false
parallel_apply: false
projects:
  - name: project1
    branch: /^main$/
    dir: project1
  - name: project2
    branch: /^main$/
    dir: project2

Additional Context

[tpolekhin]

Sorry, duplicate of #1176