Kotlin Starter

# This is executable Markdown that's tested on CI.
set -o errexit -o nounset -o xtrace
alias ~~~=":<<'~~~sh'";:<<'~~~sh'

This repo includes:

• 🧱 Latest version of Bazel and dependencies
• 📦 Curated bazelrc flags via bazelrc-preset.bzl
• 🧰 Developer environment setup with bazel_env.bzl
• 🎨 ktfmt and ktlint, using rules_lint
• ✅ Pre-commit hooks for automatic linting and formatting
• 📚 Maven package manager integration

Try it out

Before following these instructions, setup the developer environment by running direnv allow and follow any prompts. This ensures that tools we call in the following steps will be on the PATH.

First create some Kotlin source code:

mkdir src
>src/Demo.kt cat <<EOF
package app

class Demo {
  companion object {
    @JvmStatic
    fun main(args: Array<String>) {
      println("Hello from Kotlin")
    }
  }
}
EOF

Then run the BUILD file generation:

bazel run gazelle

You can check ktlint at this point:

bazel lint //src:all

This doesn't include Java support yet, so we need to run a couple commands to manually create the java_binary target:

buildozer 'new_load @rules_java//java:java_binary.bzl java_binary' src:__pkg__
buildozer 'new java_binary app' src:__pkg__
buildozer 'set main_class app.Demo' src:app
buildozer 'add runtime_deps :src' src:app

Now we can verify that the application runs and produces the expected output:

output="$(bazel run src:app)"

[ "${output}" = "Hello from Kotlin" ] || {
    echo >&2 "Wanted output 'Hello from Kotlin' but got '${output}'"
    exit 1
}