When GitHub/GitLab Auto-Merge Is Used with Atlantis Pre Workflow Hooks, the PR will be Merged Prematurely

[X-Guardian]

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Overview of the Issue

If the GitHub/GitLab auto-merge option is triggered for a PR and:

1. An Atlantis pre-workflow hook is defined for the repo
2. The pre-workflow hook is running for a plan or apply command
3. All other PR merge conditions are satisfied (approval, CI checks etc),

Then the PR will be prematurely merged when the pre-workflow hook has finished rather than when the plan/apply pipelines have finished, causing either the plan or apply to fail or for plans from the PR to be left locked.

Reproduction Steps

• Define a pre-workflow hook for a repo that takes some time to finish (giving the user chance to set the auto-merge on the PR):

repos:
  - id: /.*/
    pre_workflow_hooks:
      - description: Hook1
        run: |
          echo "Hook1"
          sleep 30s

• Create a PR and satisfy any required merge conditions (approve, plan, apply etc).
• Run a final plan or apply and select auto-merge on the PR whilst the pre-workflow hook is running.
• The PR will merge when the pre-workflow hook has finished, and then the plan or apply will fail or leave locked plans.

Environment details

• Atlantis version: 0.26.0

Additional Context

This happens because the plan or apply pipeline status is not set to 'pending' until after the pre workflow hooks are complete. This needs changing so that the relevant status is set to pending when the pre workflow hooks start.

[jamengual]

@lukemassa, here is another.