Running pre-commit hooks as GitHub Actions

In your Git repository, you may be using pre-commit hooks, as part of your pre-commit process – this works fine but sometimes, someone may pull request via the UI in GitHub for example and these pre-commit hooks won’t run natively. In this blog I am going to show you can run run pre-commit hooks as GitHub Actions

Very useful workflow to have as part of your CI checks prior to any code being merged. In my example, I will have a pre-commit that checks the format of terraform using terraform fmt

Like all pre-commit hooks, a file .pre-commit-config.yaml is required. Here is is the only I will be using with contents:

- repo:
  rev: v1.74.1
    - id: terraform_fmt
      - --args=-write=true

As you can see, I am using a pre-commit-terraform hook – they are great! In theory, install information on how to setup pre-commit hooks within your repository

Now that we have a .pre-commit-config.yaml file in our repository, we can now add this to a GitHub workflow – I used:

name: pre-commit

    branches: [main]

    runs-on: ubuntu-latest
      - name: Checkout
        uses: actions/checkout@v3

      - uses: pre-commit/action@v3.0.0
          extra_args: terraform_fmt --all-files

Link to the action

I used the pre-commit GitHub action – it is deprecated, but worked in my use case. The recommendation is to use if required

Reviewing the GitHub action, we can see the two steps ran successfully above

With successful output of the pre-commit@action terraform_fmt

[INFO] Initializing environment for
Terraform fmt............................................................Passed

Lets try merging some terraform that is not correctly formatted, I modified the terraform file which I will know that will fail the terraform_fmt check

resource "azurerm_resource_group" "tamopsrg" {
  name                = "tamopsrg"
  location    = "West Europe"

The pull-request shows the failure

Reviewing the log from the pre-commit action, we can see that it has failed on the terraform change I applied

Run pre-commit run --show-diff-on-failure --color=always terraform_fmt --all-files
Terraform fmt............................................................Failed
- hook id: terraform_fmt
- files were modified by this hook

pre-commit hook(s) made changes.
If you are seeing this message in CI, reproduce locally with: `pre-commit run --all-files`.
To run `pre-commit` as part of git workflow, use `pre-commit install`.
All changes made by hooks:
diff --git a/terraform/ b/terraform/
index 7040430..ea7a933 100644
--- a/terraform/
+++ b/terraform/
@@ -1,4 +1,4 @@
 resource "azurerm_resource_group" "tamopsrg" {
-  name                = "tamopsrg"
-  location    = "West Europe"
+  name     = "tamopsrg"
+  location = "West Europe"
Error: Process completed with exit code 1.

Very useful to have as part of your CI checks that I initially mentioned. A great way to ensure your pre-commit hooks are always ran even when attempting to pull-request via the GitHub web page!

Thanks to colleague Tim Jacomb for assisting with this as well

Repository used during this blog post

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