Keeping a project dependency graph on the README up to date automatically by always generating it on CI with a GitHub Action

1 - ci.yml

generate-dependency-graph:
    name: Generate Dependency Graph
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2

      - name: Setup Graphviz
        uses: ts-graphviz/setup-graphviz@v1

      - name: Generate Dependency Graph
        run: ./gradlew projectDependencyGraph

      - name: Commmit
        run: |
          git config --local user.email 'action@github.com'
          git config --local user.name 'GitHub Action'
          git diff --quiet && git diff --staged --quiet || git commit -am 'Update dependency graph'

      - name: Push
        uses: ad-m/github-push-action@master
        with:
          github_token: ${{ secrets.GITHUB_TOKEN }}

2 - projectDependencyGraph.gradle

// From https://github.com/JakeWharton/SdkSearch/blob/master/gradle/projectDependencyGraph.gradle
// The only difference here is the output directory.

// Add this file in your gradle directory and the following line at the bottom of your build file:
// apply from: file('gradle/projectDependencyGraph.gradle')

task projectDependencyGraph {
  doLast {
    def dot = new File(rootProject.rootDir, 'gradle/dependency-graph/project.dot')
    dot.parentFile.mkdirs()
    dot.delete()

    dot << 'digraph {\n'
    dot << "  graph [label=\"${rootProject.name}\\n \",labelloc=t,fontsize=30,ranksep=1.4];\n"
    dot << '  node [style=filled, fillcolor="#bbbbbb"];\n'
    dot << '  rankdir=TB;\n'

    def rootProjects = []
    def queue = [rootProject]
    while (!queue.isEmpty()) {
      def project = queue.remove(0)
      rootProjects.add(project)
      queue.addAll(project.childProjects.values())
    }

    def projects = new LinkedHashSet<Project>()
    def dependencies = new LinkedHashMap<Tuple2<Project, Project>, List<String>>()
    def multiplatformProjects = []
    def jsProjects = []
    def androidProjects = []
    def javaProjects = []

    queue = [rootProject]
    while (!queue.isEmpty()) {
      def project = queue.remove(0)
      queue.addAll(project.childProjects.values())

      if (project.plugins.hasPlugin('org.jetbrains.kotlin.multiplatform')) {
        multiplatformProjects.add(project)
      }
      if (project.plugins.hasPlugin('org.jetbrains.kotlin.js')) {
        jsProjects.add(project)
      }
      if (project.plugins.hasPlugin('com.android.library') || project.plugins.hasPlugin('com.android.application')) {
        androidProjects.add(project)
      }
      if (project.plugins.hasPlugin('java-library') || project.plugins.hasPlugin('java')) {
        javaProjects.add(project)
      }

      project.configurations.all { config ->
        config.dependencies
            .withType(ProjectDependency)
            .collect { it.dependencyProject }
            .each { dependency ->
              projects.add(project)
              projects.add(dependency)
              rootProjects.remove(dependency)

              def graphKey = new Tuple2<Project, Project>(project, dependency)
              def traits = dependencies.computeIfAbsent(graphKey) { new ArrayList<String>() }

              if (config.name.toLowerCase().endsWith('implementation')) {
                traits.add('style=dotted')
              }
            }
      }
    }

    projects = projects.sort { it.path }

    dot << '\n  # Projects\n\n'
    for (project in projects) {
      def traits = []

      if (rootProjects.contains(project)) {
        traits.add('shape=box')
      }

      if (multiplatformProjects.contains(project)) {
        traits.add('fillcolor="#ffd2b3"')
      } else if (jsProjects.contains(project)) {
        traits.add('fillcolor="#ffffba"')
      } else if (androidProjects.contains(project)) {
        traits.add('fillcolor="#baffc9"')
      } else if (javaProjects.contains(project)) {
        traits.add('fillcolor="#ffb3ba"')
      } else {
        traits.add('fillcolor="#eeeeee"')
      }

      dot << "  \"${project.path}\" [${traits.join(", ")}];\n"
    }

    dot << '\n  {rank = same;'
    for (project in projects) {
      if (rootProjects.contains(project)) {
        dot << " \"${project.path}\";"
      }
    }
    dot << '}\n'

    dot << '\n  # Dependencies\n\n'
    dependencies.forEach { key, traits ->
      dot << "  \"${key.first.path}\" -> \"${key.second.path}\""
      if (!traits.isEmpty()) {
        dot << " [${traits.join(", ")}]"
      }
      dot << '\n'
    }

    dot << '}\n'

    def p = 'dot -Tpng -O project.dot'.execute([], dot.parentFile)
    p.waitFor()
    if (p.exitValue() != 0) {
      throw new RuntimeException(p.errorStream.text)
    }

    println("Project module dependency graph created at ${dot.absolutePath}.png")
  }
}

3 - README

And here's how to show the (automatically kept) up to date dependency graph for the project in a README file:

![](gradle/dependency-graph/project.dot.png)