Kotlin Project Guardrails

✓ Policy Beta Devex Build And Ci

Enforce Kotlin project standards: build manifest presence, Kotlin version pinning, Gradle wrapper commit, dependency locking, test source layout, and detekt/ktlint configuration. Supports Gradle (Kotlin & Groovy DSL) and Maven (kotlin-maven-plugin).

Add kotlin to your lunar-config.yml:

uses: github://earthly/lunar-lib/policies/kotlin@v1.0.5

Get Started View on GitHub

Included Guardrails

This policy includes 7 guardrails that enforce standards for your devex build and ci.

Guardrail

`build-tool-manifest-exists`

Ensures the project has a recognised Kotlin build manifest: build.gradle.kts (Gradle Kotlin DSL), build.gradle (Gradle Groovy DSL applying a Kotlin plugin), or pom.xml with the kotlin-maven-plugin. Required for any Kotlin project so that the build is reproducible and tooling-discoverable.

build.gradle.kts build.gradle pom.xml gradle kotlin-maven-plugin manifest

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Guardrail

`kotlin-version-pinned`

Ensures the Kotlin compiler version is declared — via the Gradle kotlin("jvm") version "..." / id("org.jetbrains.kotlin.jvm") plugin, <kotlin.version> in pom.xml, or a kotlin entry in gradle/libs.versions.toml. Pinning the compiler version prevents drift between developers and CI.

kotlin version kotlin plugin version pinning

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Guardrail

`min-kotlin-version`

Ensures the declared Kotlin compiler version meets the configured minimum (default: "1.8"). Reads .lang.kotlin.version. Skips when the version is not detected — pair with kotlin-version-pinned if you want presence to be enforced too.

kotlin version version floor compatibility security

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Guardrail

`build-tool-wrapper-exists`

Ensures the Gradle wrapper (gradlew + gradle/wrapper/) is committed for Gradle projects. Wrappers pin the build tool version and give reproducible builds without a pre-installed Gradle. Skips for Maven-only projects.

gradle wrapper gradlew reproducible builds

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Guardrail

`dependencies-locked`

Ensures dependencies are locked for reproducible builds via Gradle dependency locking (gradle.lockfile). Informational by default — most Kotlin/Gradle projects do not lock dependencies, but doing so produces reproducible CI builds.

gradle.lockfile lockfile reproducibility dependency locking

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Guardrail

`test-directory-exists`

Ensures a src/test/kotlin directory (or the equivalent for Android / Multiplatform layouts) exists with test sources. Skips on non-Kotlin projects.

src/test/kotlin junit kotest testing test layout

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Guardrail

`linter-configured`

Ensures a Kotlin static-analysis / formatting tool is configured — detekt (detekt.yml) or ktlint. These enforce consistent code quality and formatting and are the de facto standard for Kotlin. Informational.

detekt ktlint formatting static analysis code style

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How Guardrails Fit into Lunar

Lunar guardrails define your engineering standards as code. They evaluate data collected by integrations and produce pass/fail checks with actionable feedback.

Policies support gradual enforcement—from silent scoring to blocking PRs or deployments—letting you roll out standards at your own pace without disrupting existing workflows.

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Required Integrations

This policy evaluates data gathered by one or more of the following integration(s). Make sure to enable them in your lunar-config.yml.

Collector LanguagesBuild Required

Kotlin Collector

Provides Kotlin project metadata

Configuration

Configure this policy in your lunar-config.yml.

Inputs

Input	Required	Default	Description
`min_kotlin_version`	Optional	`1.8`	Minimum required Kotlin compiler version (e.g., "1.8", "1.9", "2.0"). Compared with semantic-version semantics — "1.8" matches 1.8.x and above, but rejects 1.7.x.

Documentation

View on GitHub

Kotlin Project Guardrails

Enforce Kotlin-specific project standards including build manifest presence, version pinning, wrapper commit, dependency locking, test layout, and static-analysis configuration.

Overview

This policy validates Kotlin projects against best practices for build configuration, version pinning, dependency reproducibility, testing conventions, and code quality. All checks skip gracefully on non-Kotlin projects (i.e., .lang.kotlin missing). Supports Gradle (Kotlin & Groovy DSL) and Maven (with kotlin-maven-plugin) build systems.

Policies

This plugin provides the following policies (use include to select a subset):

Policy	Description	Failure Meaning
`build-tool-manifest-exists`	Validates `build.gradle.kts`, `build.gradle`, or `pom.xml` exists	Project lacks a recognised Kotlin build manifest
`kotlin-version-pinned`	Validates the Kotlin compiler version is declared	Missing Kotlin plugin/`<kotlin.version>` declaration
`min-kotlin-version`	Validates declared Kotlin version meets `min_kotlin_version` (default `1.8`)	Kotlin version below the configured minimum
`build-tool-wrapper-exists`	Validates the Gradle wrapper is committed	Missing `gradlew` (Gradle projects only)
`dependencies-locked`	Validates `gradle.lockfile` is present	No lockfile committed (informational)
`test-directory-exists`	Validates `src/test/kotlin` exists	No test sources detected
`linter-configured`	Validates detekt or ktlint is configured	Neither detekt nor ktlint configured (informational)

Required Data

This policy reads from the following Component JSON paths:

Path	Type	Provided By
`.lang.kotlin`	object	`kotlin` collector
`.lang.kotlin.build_gradle_kts_exists`	boolean	`kotlin` collector
`.lang.kotlin.build_gradle_exists`	boolean	`kotlin` collector
`.lang.kotlin.pom_xml_exists`	boolean	`kotlin` collector
`.lang.kotlin.version`	string	`kotlin` collector
`.lang.kotlin.build_systems`	array	`kotlin` collector
`.lang.kotlin.gradlew_exists`	boolean	`kotlin` collector
`.lang.kotlin.lockfile_exists`	boolean	`kotlin` collector
`.lang.kotlin.test_directory_exists`	boolean	`kotlin` collector
`.lang.kotlin.detekt_configured`	boolean	`kotlin` collector
`.lang.kotlin.ktlint_configured`	boolean	`kotlin` collector

Installation

Add to your lunar-config.yml:

policies:
  - uses: github://earthly/lunar-lib/policies/kotlin@main
    on: ["domain:your-domain"]  # replace with your own domain or tags
    enforcement: report-pr
    # include: [build-tool-manifest-exists, kotlin-version-pinned]  # Only run specific checks

Examples

Passing Example

{
  "lang": {
    "kotlin": {
      "build_gradle_kts_exists": true,
      "version": "1.9.22",
      "build_systems": ["gradle"],
      "gradlew_exists": true,
      "lockfile_exists": true,
      "test_directory_exists": true,
      "detekt_configured": true,
      "ktlint_configured": false
    }
  }
}

Failing Example

{
  "lang": {
    "kotlin": {
      "build_gradle_kts_exists": false,
      "build_gradle_exists": false,
      "pom_xml_exists": false,
      "version": "",
      "build_systems": [],
      "gradlew_exists": false,
      "lockfile_exists": false,
      "test_directory_exists": false,
      "detekt_configured": false,
      "ktlint_configured": false
    }
  }
}

Failure messages:

"No Kotlin build manifest found. Add build.gradle.kts (Gradle Kotlin DSL), build.gradle (Groovy DSL), or pom.xml with kotlin-maven-plugin."
"Kotlin compiler version not declared. Add the Kotlin Gradle plugin with a version (e.g. kotlin(\"jvm\") version \"1.9.22\") or set <kotlin.version> in pom.xml."
"Kotlin version 1.7.20 is below minimum 1.8. Update the Kotlin plugin version."
"Gradle wrapper not found. Run 'gradle wrapper' and commit gradlew, gradlew.bat, and gradle/wrapper/."
"No dependency lockfile found. Enable Gradle dependency locking and commit gradle.lockfile for reproducible builds."
"No test sources found. Create src/test/kotlin/ and add JUnit, Kotest, or MockK tests."
"No Kotlin linter configured. Add detekt (detekt.yml) or ktlint for consistent code quality."

Remediation

build-tool-manifest-exists

For Gradle (Kotlin DSL): create build.gradle.kts at the repo root and apply a Kotlin plugin
For Gradle (Groovy DSL): create build.gradle applying org.jetbrains.kotlin.jvm
For Maven: add pom.xml with the kotlin-maven-plugin in <plugins>

kotlin-version-pinned

In build.gradle.kts, add to the plugins {} block: kotlin("jvm") version "1.9.22" (or your target version)
In build.gradle (Groovy): id 'org.jetbrains.kotlin.jvm' version '1.9.22'
In pom.xml: set <kotlin.version>1.9.22</kotlin.version> and reference it in the kotlin-maven-plugin config

min-kotlin-version

Update the Kotlin plugin version (or <kotlin.version>) to a version at or above min_kotlin_version
Run ./gradlew build (or mvn verify) to confirm the project still compiles on the new version
Review the Kotlin changelog for any breaking language/stdlib changes between versions

build-tool-wrapper-exists

Run gradle wrapper --gradle-version <version> to generate the wrapper
Commit gradlew, gradlew.bat, and the gradle/wrapper/ directory
Use ./gradlew in CI so the pinned version is always used

dependencies-locked

Enable dependency locking in build.gradle.kts:

dependencyLocking { lockAllConfigurations() }

Run ./gradlew dependencies --write-locks to generate gradle.lockfile
Commit gradle.lockfile to version control

test-directory-exists

Create src/test/kotlin/
Add a test framework dependency (JUnit 5, Kotest, or MockK)
Add at least one test file under src/test/kotlin/

linter-configured

For detekt, apply the plugin in build.gradle.kts:
```
plugins { id("io.gitlab.arturbosch.detekt") version "1.23.5" }
```
and commit a detekt.yml config at the repo root
For ktlint, apply id("org.jlleitschuh.gradle.ktlint") version "12.1.0"
Run ./gradlew detekt (or ktlintCheck) to verify the configuration

Open Source

This policy is open source and available on GitHub. Contribute improvements, report issues, or fork it for your own use.

View Repository

Common Use Cases

Explore how individual guardrails work with specific integrations.

Build Tool Manifest Exists + Kotlin Collector Ensures the project has a recognised Kotlin build manifest: `build.gradle.kts`...

→

Kotlin Version Pinned + Kotlin Collector Ensures the Kotlin compiler version is declared — via the Gradle `kotlin("jvm")...

→

Min Kotlin Version + Kotlin Collector Ensures the declared Kotlin compiler version meets the configured minimum...

→

Build Tool Wrapper Exists + Kotlin Collector Ensures the Gradle wrapper (`gradlew` + `gradle/wrapper/`) is committed for...

→

Dependencies Locked + Kotlin Collector Ensures dependencies are locked for reproducible builds via Gradle dependency...

→

Test Directory Exists + Kotlin Collector Ensures a `src/test/kotlin` directory (or the equivalent for Android...

→

Linter Configured + Kotlin Collector Ensures a Kotlin static-analysis / formatting tool is configured — detekt...

→

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