Continuous Integration With Netlify Build Plugins

May 02, 20202min to read • 475 words

Netlify is a great tool to easily deploy and host your static website without any hassle but when it comes to a real-life continuous integration it can become a bit tricky. For this blog, we used a GitHub workflow to run unit tests, lint the code and check the yarn.lock file for uncommitted changes. Therefore, we disabled Netlify’s auto-publishing feature and deployed our blog manually after all checks passed. It certainty works, but we would love to stay in Netlify’s ecosystem and use one tool to deploy our application.

So, what are Netlify Build Plugins?

Netlify build plugins are JavaScript functions which get executed in Netlify’s build pipeline. They just released the beta version and you can enable it for your application right in the Netlify app. With that, you can basically extend the build pipeline and do whatever you want (well more or less).

There are already good examples like:

  • Running Cypress end-to-end tests
  • Cache your Gatsby cache and improve the build time significantly
  • Automatically generate a sitemap

I can’t wait to see more awesome plugins popping up in the next months! Besides general plugins, we can also build our custom plugin and put it next to our code.

CI as a plugin

So in this example, we want to run some checks before Netlify actually builds the application:

module.exports = {
  async onPreBuild({ utils }) {
    try {
      await'git diff --exit-code yarn.lock');
    } catch (error) {
        'Please commit the latest changes in your yarn.lock file!'

    try {
      await'yarn lint');
      await'yarn test:ci');
      await'yarn build-storybook');
    } catch (error) {'CI failed!');

What’s happening here?

  1. First, we check the yarn.lock file for uncommitted changes after Netlify installed the dependencies. That way we ensure the integrity of the dependencies.
  2. After that, we lint the code, run unit tests and build Storybook.

Last but not least, just tell Netlify you have a new plugin by extending the netlify.toml file:

package = "./.plugins/ci"

That’s it! Our CI pipeline in pure JavaScript! Of course, it’s a simple example but already enough for us to validate our application. Netlify passes some input to the plugin we can use to interact with the build pipeline. As you can see, we use a helper function to run shell scripts and another one to fail the build.

Right now it’s possible to hook into the following steps of their build pipeline:

onInitRuns before anything else
onPreBuildBefore build commands are executed
onBuildBuild commands are executed
onPostBuildAfter Build commands are executed
onSuccessRuns on build success
onErrorRuns on build error
onEndRuns on build error or success


Netlify build plugins can be really helpful to have one tool for CI and CD but it’s still beta software and some features are definitely missing. To speed up the build pipeline, it would be cool to run plugins in parallel, for instance, there is no reason for us to run our checks in sequence. Another cool feature would be to have GitHub pull request checks for every plugin. Just imagine you could already see in GitHub which plugin failed and what error was thrown. Nevertheless, it’s worth checking out build plugins and bringing your development setup to the next level!

In case you are totally excited now, here is a reading list: