Add Merged PRs to a Project Using Github Actions - github-actions

Question

I'm attempting to create an Action that automatically adds a merged PR to a project so the PR can be reviewed for documentation needs. The key here is that the PR should be added to the project after it's been merged into main. From what I can tell, Github Actions don't work directly with merged PRs for the pull_request webhook.
Has anybody managed to do this or have any tips? My initial thought is to do something like:
name: Add-Merged-PRs
# Run this workflow every time a PR is merged into the main branch
on: push
branches:
- main
jobs:
# Take the PR that was merged and add it to a specified project.

Answer 1

You can use the pull_request event and narrow it down to "has been closed" and "was merged" using the types and branches properties of pull_request, then check in the github.event.pull_request context that the merged property is true.
All together, for a project named "Test" and a column "Merged PRs", using the GitHub CLI to make API calls, a workflow might look like this:
name: Add merged PRs to project
# When a PR into main is closed or merged
on:
pull_request:
types:
- closed
branches:
- main
jobs:
addpr:
name: Add PR to project
# PR must must be merged, not closed
if: github.event.pull_request.merged
runs-on: ubuntu-20.04
steps:
- name: Add PR to project board
env:
GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
run: |
projectid=$(gh api "repos/${{ github.repository }}/projects" \
-H "Accept: application/vnd.github.inertia-preview+json" \
| jq '.[] | select(.name == "Test").id')
columnid=$(gh api "projects/$projectid/columns" \
-H "Accept: application/vnd.github.inertia-preview+json" \
| jq '.[] | select(.name == "Merged PRs").id')
gh api "projects/columns/$columnid/cards" \
-H "Accept: application/vnd.github.inertia-preview+json" \
-F "content_type=PullRequest" \
-F "content_id=${{ github.event.pull_request.id }}"
For reference and to see how "closed with unmerged commits" and "properly merged" are told apart, see the docs for the pull_request payload object.