Platformless

#Before we get started

This tutorial continues after “[Getting Started][started]” - it’s not required that you have danger ci set up though.

#Locality

With Danger, the typical flow is to help you can check rules on CI and get feedback inside your PR. With Peril you can move those rules to run on an external server making feedback instant. danger local provides a somewhat hybrid approach.

danger local provides a way to run a Dangerfile based on git-hooks. This let’s you run rules while you are still in the same context as your work as opposed to later during the code review. Personally, I find this most useful on projects when I ship 90% of the code to it.

#How it works

Where danger ci uses information from the Pull Request to figure out what has changed, danger local naively uses the local differences in git from master to the current commit to derive the runtime environment. This is naive because if you don’t keep your master branch sync, then it will be checking across potentially many branches.

Inside a Dangerfile danger.github and danger.bitbucket will be falsy in this context, so you can share a Dangerfile between danger local and danger ci as long as you verify that these objects exist before using them.

When I thought about how I wanted to use danger local on repos in the Danger org, I opted to make a separate Dangerfile for danger local and import this at the end of the main Dangerfile. This new Dangerfile only contains rules which can run with just danger.git, e.g. CHANGELOG/README checks. I called it dangerfile.lite.ts.

#Getting it set up

You need to add both Danger and husky to your project:

yarn add --dev danger husky

When husky is in your dependencies, git-hooks are set up to respond according to matching names in the "scripts" section of your package.json. We want to use a pre-push hook to let danger local run before code has been submitted.

"scripts": {
  "prepush": "yarn build; yarn danger:prepush",
  "danger:prepush": "yarn danger local --dangerfile dangerfile.lite.ts"
  // [...]

Yes, it’s a pre-push hook and the script is prepush, husky removes the dashes. If master isn’t the branch which you want as a reference then you can use --base dev to change the comparison base.