Github Action : Stop the action if PR already exists

Question

I am creating auto PR via GitHub action, So whenever a new push happens on dev branch. automatically a PR is created from dev to master

I want to change: If already a PR exists ( master <- dev ) no need to run this action, so how can I check if already PR exists?

Github Action

name: Pull Request Action
on:
    push:
        branches: ['dev']

jobs:
    create-pull-request:
        runs-on: ubuntu-latest
        steps:
            - name: Create Pull Request
              uses: actions/github-script@v6
              with:
                  script: |
                      const { repo, owner } = context.repo;
                      const result = await github.rest.pulls.create({
                        title: 'Master Sync : Auto Generated PR',
                        owner,
                        repo,
                        head: '${{ github.ref_name }}',
                        base: 'master',
                        body: [
                          'This PR is auto-generated by',
                          '[actions/github-script](https://github.com/actions/github-script).'
                        ].join('\n')
                      });
                      github.rest.issues.addLabels({
                        owner,
                        repo,
                        issue_number: result.data.number,
                        labels: ['feature', 'automated pr']
                      });

Answer 1

There's no condition that you could use directly in an if step on the job itself, but you could use the GitHub CLI to see if there is such a PR already, and then exit early:

steps:
  - name: Check if PR exists
    id: check
    env:
      GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
    run: |
      prs=$(gh pr list \
          --repo "$GITHUB_REPOSITORY" \
          --head 'dev' \
          --base 'master' \
          --json title \
          --jq 'length')
      if ((prs > 0)); then
          echo "skip=true" >> "$GITHUB_OUTPUT"
      fi

  - name: Create pull request
    if: '!steps.check.outputs.skip'
  # ...

Answer 2

I used this successfully for the bulk of it, but the | length pipe did not work. I'm not as familiar with bash, but the prs array always had 1 element in it regardless of if there was or wasn't a PR. But the first element in the array was of length 0 when there were no PRs. This is what I ended up with:

  name: Check if PR already exists
    id: check-pr-exists
    env:
      GH_TOKEN: ${{ github.token }}
    run: |
      prs=$(gh pr list -B targetBranch -H sourceBranch)  
      # Even when there are no PRs, this array always seems to have 1 result
      echo Size of PRS ARRAY: ${#prs[@]}
      # Locally, it seems the gh cli says 'no pull requests match your search..' but not here.
      # The first element exists but is of length 0
      echo Length of PRS[0] string: ${#prs[0]}
      
      if ((${#prs[@]} > 0 && ${#prs[0]} != 0 )); then
        echo skipping PR creation
        echo "skip=true" >> "$GITHUB_OUTPUT"
      fi
  - name: Create PR
    if: '!steps.check-pr-exists.outputs.skip'
    run: |
      gh pr create -B targetBranch -H source Branch .....