build.gradle

// 各モジュールの build.gradle で設定する
// gradle/ktlint.gradle に記述を切り出して各 build.gradle で apply from: rootProject.file('gradle/ktlint.gradle') とした方が良いかも

// ...

configurations {
    ktlint
}

dependencies {
    ktlint "com.pinterest:ktlint:0.34.2"
}

task ktlint(type: JavaExec, group: "verification") {
    description = "Check Kotlin code style."
    classpath = configurations.ktlint
    main = "com.pinterest.ktlint.Main"
    args "--android", "--color", "--reporter=plain", "--reporter=checkstyle,output=${buildDir}/reports/ktlint-results.xml", "src/**/*.kt"
    ignoreExitValue true
}

check.dependsOn ktlint

check-pull-request.yml

name: Check pull request

on: pull_request

jobs:
  check:
    name: Check pull request
    runs-on: ubuntu-18.04
    steps:
      - uses: actions/checkout@v1
      - uses: actions/setup-java@v1
        with:
          java-version: 1.8
      - uses: actions/setup-ruby@v1
        with:
          ruby-version: '2.6'
          architecture: 'x64'
      - name: Get gem directory
        id: gem-dir
        run: echo "::set-output name=dir::$(gem environment gemdir)"
      - uses: actions/cache@v1 # ~/.gradle配下は400Mを超えるので現状ではキャッシュできない..
        with:
          path: ${{ steps.gem-dir.outputs.dir }}
          key: ${{ runner.os }}-gem-${{ hashFiles('.github/workflows/check-pull-request.yml') }}
          restore-keys: ${{ runner.os }}-gem-
      - name: Run ktlint
        run: ./gradlew ktlint
      - name: Run Android Lint # フレーバー・ビルドタイプがモジュール毎に異なる場合はモジュール毎に ./gradlew app:lintHoge する
        run: ./gradlew lintDebug
      - name: Set up and run Danger
        env:
          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          gem install danger
          gem install danger-checkstyle_format
          gem install danger-android_lint
          danger
      - name: Run Unit Test # フレーバー・ビルドタイプがモジュール毎に異なる場合はモジュール毎に ./gradlew app:lintHogeUnitTest する
        run: ./gradlew testDebugUnitTest

  notify-success:
    name: Notify success
    needs: [check]
    runs-on: ubuntu-18.04
    steps:
      - name: Notify Slack
        run: |
          curl -X POST \
               -H 'Content-type: application/json' \
               -H 'Authorization: Bearer ${{ secrets.SLACK_BOT_TOKEN }}' \
               -d '{"channel":"kusu_test_github","username":"github-actions","icon_url":"https://github.githubassets.com/images/modules/logos_page/GitHub-Mark.png","text":"Success"}' \
               https://slack.com/api/chat.postMessage

  notify-failure:
    name: Notify failure
    needs: [check]
    if: failure()
    runs-on: ubuntu-18.04
    steps:
      - name: Notify Slack
        run: |
          curl -X POST \
               -H 'Content-type: application/json' \
               -H 'Authorization: Bearer ${{ secrets.SLACK_BOT_TOKEN }}' \
               -d '{"channel":"kusu_test_github","username":"github-actions","icon_url":"https://github.githubassets.com/images/modules/logos_page/GitHub-Mark.png","text":"Failure"}' \
               https://slack.com/api/chat.postMessage

Dangerfile

github.dismiss_out_of_range_messages

# ktlint
Dir.glob("**//build/reports/ktlint-results.xml").each { |report|
    checkstyle_format.base_path = Dir.pwd
    checkstyle_format.report report.to_s
}

# Android Lint
Dir.glob("**//build/reports/lint-results*.xml").each { |report|
    android_lint.skip_gradle_task = true
    android_lint.report_file = report.to_s
    android_lint.filtering = true
    android_lint.lint(inline_mode: true)
}