Trigger Github Actions only when PR is merged

Question

I have a github actions yaml file as follows:

name: Test deployment
on:
  pull_request:
    branches:
    - master

jobs:
  deploy:
    runs-on: ubuntu-18.04
    steps:
    - name: Random name
      run: date

When I raise a PR from a branch to master branch, Github Action gets triggered. So, I updated my YAML to:

name: Test deployment
on:
  pull_request:
    types:
    - closed
    branches:
    - master

Now it is triggered when I merge the PR rather than while raising it. But it also gets triggered when I close the PR without merging it.

I found nothing like merged type in docs

Even the following syntax i tried does not work as expected:

jobs:
  ...
    if: github.event_name == 'pull_request' && github.event.action == 'closed'

Can anyone pls help me out here? Is it possible for me to check if the PR is approved by atleast one reviewer? (I can enable branch protection, but wanted to know if any option exists for doing it in github actions)

Answer 1

There is no pull-request-merged event.

The closest thing you can get is to subscribe to push event, since a merged PR will always create a push event to the branch it's being merged onto.

If you only care about PRs to master then you can specify that:

on:
  push:
    branches:
      - master

The other thing you can do is filter on each step individually

      - name: Do something
        if: github.event_name == 'pull_request' && github.event.action == 'closed' && github.event.pull_request.merged == true
        run: ...

(Edit, as of 2022) Per the GitHub docs, this should be possible now via:

on:
  pull_request:
    types:
      - closed

jobs:
  if_merged:
    if: github.event.pull_request.merged == true
    runs-on: ubuntu-latest
    steps:
    - run: |
        echo The PR was merged