Since you need the notification content to be customizable, I would go with notification action + slack workflow (if your workspace has access to those).
Create a notification workflow
- Use the Workflow Builder to create a new workflow
- Choose
From a webhook as the workflow trigger and define data variables. These are the expected fields that your GitHub action will post to the webhook URL, e.g. title, author, pullRequestLink etc. See Opened PR event payload for a list of fields available during this workflow event.
- Choose
Send a message as the workflow action and define the message template. The interface lets you use the variables defined in the previous step as placeholders.
Set up a GitHub workflow to call the webhook
Use a GitHub action to post a structured payload to the workflow URL. The workflow can look something like this:
name: PR creation event notification
on:
pull_request:
- opened
- reopened
jobs:
notify:
name: PR notification
runs-on: [ubuntu-latest]
steps:
- name: Post message
uses: slackapi/[email protected]
env:
SLACK_WEBHOOK_URL: the webhook URL, preferably a GitHub secret
with:
payload: |
{
"title": ${{ toJson(github.event.pull_request.title) }},
"author": ${{ toJson(github.event.pull_request.user.login) }},
"link": ${{ toJson(github.event.pull_request.html_url) }}
}
Using toJson() ensures that special characters are escaped properly (the payload argument must be a valid JSON).
Reusing the workflow
This GHA feature wasn't available at the time the original question was asked.
If you expect to use the workflow in a large number of repositories, it's possible to make it reusable (to simplify maintenance). In that case, the generic workflow would have a workflow_call trigger:
name: Reusable Slack notification workflow
on:
workflow_call:
inputs:
workflow-event:
required: true
type: string
secrets:
slackWebhookUrl:
required: true
jobs:
notify:
name: PR notification
runs-on: [ubuntu-latest]
steps:
- name: Post message
uses: slackapi/[email protected]
env:
SLACK_WEBHOOK_URL: the webhook URL, preferably a GitHub secret
with:
payload: |
{
"title": ${{ toJson(fromJson(inputs.workflow-event).title) }},
"author": ${{ toJson(fromJson(inputs.workflow-event).user.login) }},
"link": ${{ toJson(fromJson(inputs.workflow-event).html_url) }}
}
Let's assume this file is located at /.github/workflows/.generic-slack-notification.yml in your-reusable-workflow-repo repository within your-org organization.
Notice that instead of referencing github.event.pull_request (which is not available, since the reusable workflow is triggered by a different event), it now uses fromJson(inputs.workflow-event) to parse the data from its input. The input is provided by the individual "caller workflows" from your repositories like this:
name: PR creation event notification
on:
pull_request:
- opened
- reopened
jobs:
notify:
name: PR notification
runs-on: [ubuntu-latest]
steps:
- name: Post message
uses: your-org/your-reusable-workflow-repo/.github/workflows/.generic-slack-notification.yml@main
with:
workflow-event: ${{ toJson(github.event.pull_request) }}
secrets:
slackWebhookUrl: ${{ secrets.SLACK_DEPLOYMENT_WEBHOOK_URL }}
