github.sha isn't the value expected

[anderspitman]

I’m trying to retrieve the SHA from the commit that triggers the action. So if I make a commit and then do a push, within that push action handler I want to get that commit SHA. My goal is to build a URL based around the SHA and then comment on the PR with the URL (using https://github.com/unsplash/comment-on-pr).

I expected github.sha to work, but I have no idea where the values it’s giving me are coming from. They don’t match any of the commits in the repo. Here’s the code I tried:

name: CI
on:

push:

branches: [master]

pull_request:

branches: [master]

jobs:

example:

name: sample comment

runs-on: ubuntu-latest

steps:

- name: comment PR

uses: unsplash/comment-on-pr@master

env:

GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

with:

msg: "example.com/${{github.sha}}"

[Yanjingzhu]

@anderspitman When a workflow is triggered by pull request event, the github.ref will be refs/pull/<id>/merge. And the github.sha will be the pre merge commit id. If you have a pull request from dev to master, github.sha is not the commit which you pushed to dev.  

pr event.png768×699 29.5 KB

You need to use github.event.pull_request.head.sha to get the commit id which you pushed to dev. 

And based on my test when the workflow is triggered by push to master,  comment PR step will fail. 

So you could change your workflow file to 

name: CI
on:
  pull_request:
    branches: [master]
jobs:

example:

name: sample comment

runs-on: ubuntu-latest

steps:

- name: comment PR

uses: unsplash/comment-on-pr@master

env:

GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

with:

msg: "example.com/${{github.event.pull_request.head.sha}}"

[wheelerlaw]

Is there an explanation for this counter-intuitive behavior? It really seems like poor design to have github.ref refer to anything but the head of the feature branch.

[anderspitman]

Sorry for the late response. This does indeed do the trick. Thanks!

[mongodben]

i recently encountered the same issue, but github.event.pull_request.head.sha was not working for me.

what worked was using github.event.workflow_run.head_sha. hope this helps!

[RomeroGaliza]

depends on the event you're dealing with: pull_request vs. workflow_run. ;)