A simple way to format your Dataform project before each Git commit

If you work with Dataform core in your local environment (instead of using the GCP Cloud IDE), you will want to run dataform format before committing your code to neatly format your .sqlx and .js files. This can be easily automated in Git by creating a pre-commit hook. This short tutorial will show you how to create such a pre-commit hook and share it with the rest of your team. I asked ChatGPT to create this pre-commit hook for me, and it got it almost right! I just had to adjust a few things to make it work correctly. The tutorial assumes you already have the Dataform CLI installed on your machine. If not, please follow the documentation.

The pre-commit hook

In your Dataform project’s root directory, create a new directory called .githooks and inside that directory, create a file called pre-commit, so it should look like this: your_dataform_project/.githooks/pre-commit. Edit the pre-commit file and paste the following content:

#!/bin/sh

# Stash any unstaged changes
git stash -q --keep-index

# Run dataform format
dataform format

# Check if the dataform format command changed any files
CHANGED_FILES=$(git diff --name-only definitions/ includes/)
if [ -n "$CHANGED_FILES" ]; then
    echo "Some files were formatted by dataform. Please add the changes to your commit."
    git stash pop -q
    exit 1
fi

# Reapply the stash to restore unstaged changes
git stash pop -q

Save the file. Now you need to make this script executable. In Linux, run the command chmod +x .githooks/pre-commit.

This shell script first stashes any unstaged changes, because we only want the hook to fail if dataform format modifies any files. After that, it runs dataform format and then checks if it changed any files in the definitions/ and includes/ directories. If so, it will notify you, reapply the stash and exit with status code 1. If no files were modified, it will reapply the stash and exit normally.

Activate the pre-commit hook

Now all we have to do, is to tell Git that the newly created directory .githooks contains the Git hooks for this project: git config --local core.hooksPath .githooks/.

You can now test your newly created hook. Make some changes to any .sqlx or .js files in the definitions/ or includes/ directories, run git add to stage the changes, then run git commit. If all goes well, Git will run the shell script before the commit.

Commit your changes

Make sure that the newly created .githooks directory and its contents make it to the main branch of your Dataform project’s repository. Now the rest of your team can easily configure the pre-commit hook. All they have to do is to run git config --local core.hooksPath .githooks/. You could update your repository’s README.md with this information.

Next steps

Now that you have a working pre-commit hook, you should think about adding this check in your CI/CD workflow. With the pre-commit shell script, this should be relatively simple to do. This will ensure that any code committed to your repository is correctly formatted. I won’t show you how to do this in this tutorial, because it greatly depends on the automation server your team is using (Jenkins, GitHub Actions etc.)