Spotless android code
We will Automate code formatting using Spotless, git hook and ktlint in this example.
Spotless
Start by adding a dependency in project level gradle file
add a new gradle file spotless.gradle in a project root folder
and in a module-level gradle file
You can sync and run./gradlew spotlessCheck now to check for formatting issues, or ./gradlew spotlessApply to fix those issues. If it can fix it automatically, it will; else, it will throw an error.
ktlint
In this example, our spotless is set up to use ktlint for kotlin files.
You can setup spotless for other language and with other standards like diktat or ktfmt . you can find everything you need here.
We defined a path to the editor config while setting up ktlint as “${project.rootDir}/spotless/.editorconfig”. Using that editor config, we can enable/disable certain rules in ktlint. Read about ktlint rules here and tweak the config like below to have rules according to your project need.
Git hook
Instead of running the gradle task spotlessApply manually, we can automate this to run before every commit with the help of git hooks. Create a file with the name pre-commit inside .git/hooks folder of your project, and copy-paste the code below. Which will run the spotlessApply gradle command and will abort the commit if it fails. If it succeeds, then it will proceed with your commit, including the spotless fixes for your staged files.
You now have a pre-commit hook setup for your project. Try to commit, and you should see that it's working for you. Only for you. If we want other devs to have this setup, we will have to ask all of them to do it on their device. So, we will automate this for them. We will add a gradle task to copy pre-commit file into .git/hooks folder when a project is built. Hoping whoever works on this project will build the project at least once before committing. Let’s add that pre-commit file into a folder called scripts in the project root. Then add a gradle task to copy that script into the git hooks folder. we will do that in our spotless gradle file. Your spotless gradle file should look like this
Done. Now all devs will see a git pre-commit hook when they clone and build this project. For already cloned repos, it will be set up on the next project build.
This git hooks can be skipped when committing a code, so if you really want to enforce the formatting before any PR is merged, add spotlessCheck in your PR validation. This Git hook for spotless is just a convenience for a dev to make sure that the lint issue is fixed before submitting any change for review.
