mkohm / detekt-hint

Detection of design principle violations in Kotlin as a plugin to detekt.

detekt-hint (Attention: Looking for developers)

Detection of design principle violations in Kotlin added as comments on pull requests.

Getting started | 🏁 Roadmap | 💭 Ask a question | 📖 Documentation

detekt-hint is a plugin for detekt that includes detection of violation of programming principles. Since such violations are hard to detect with low false-positive rates, detekt-hint will provide hints during QA, minimizing noise during development. The idea is that a higher false-positive rate can be accepted if the detection could be of high value, and is easy to ignore. Detections on the architectural level of code is therefore most likely to provide value.

Through integration with Danger comments are added to the PR. Getting feedback directly on the PR makes it easy to ignore possible false-positives. Comments also include context and tips, making it easier for the developer to make the correct decisions.

Contributions are very much welcome and if you like the project - help me out with a ⭐. Especially help in which rules to implement, how to implement them and how to reduce the false-positives.

Currently supported detections

✅ Use composition instead of inheritance - Will help developer ensure Liskov Substitution Principle is not violated. Will not report if you inherit from third-party libraries.

✅ Lack Of Cohesion of Methods - Notifies you if the LCOM value is too high.

✅ Interface Segregation Principles - Notifies you if you implement methods that the class does not need.

✅ Open-Closed Principle - This rule reports use of switching on enums and classes, which may be a sign of violation the open closed principle.

Interface Segregation Principle

Single Responsibility Principle

Open-Closed Principle

Using detekt-hint

If you just want to analyze some code without bothering with the Danger integration (which really defeats the purpose of the tool) head to the command line section.

With Github Actions

1. Configure a detekt-hint-config.yml to include detekt-hint rules and put it in a folder called "config" in your root project folder.

config/detekt-hint-config.yml

detekt-hint:
  UseCompositionInsteadOfInheritance:
    active: true
    yourUniquePackageName: "io.github.mkohm"
  LackOfCohesionMethods:
    active: true
    threshold: "0.8"
  InterfaceSegregationPrinciple:
      active: true
  OpenClosedPrinciple:
      active: true

Make sure you enter your unique package name in the configuration for the UseCompositionInsteadOfInheritance rule.

2. Create a github action using the detekt-hint docker action.

.github/workflows/detekt-hint.yml

name: detekt hint

on:
  pull_request:
    branches:
      - '*'

jobs:
  gradle:
    strategy:
      matrix:
        os: [ubuntu-latest]
        jdk: [11]
    runs-on: ${{ matrix.os }}
    if: ${{ !contains(github.event.head_commit.message, 'detekt hint skip') }}
    env:
      JDK_VERSION:  ${{ matrix.jdk }}
    steps:
      - name: Checkout Repo
        uses: actions/checkout@v2
        
      - name: Run detekt hint
        uses: mkohm/[email protected]
        with:
          github-api-token: ${{ secrets.GITHUB_TOKEN }}

3. Create a PR and see detekt-hint run as a separate action.

Having trouble? Please create an issue or contact me on the kotlinlang Slack (username: mkohm), and i will help you out.

With the command line

If you only want to do some analysis on your code without the power of Danger commenting on your PR you can use the tool from the command line. You must first clone detekt and detekt-hint repositories, and then build the required jars:

git clone https://github.com/Mkohm/detekt-hint && git clone https://github.com/arturbosch/detekt && cd detekt-hint && ./gradlew jar && cd ../detekt/ && ./gradlew build shadowJar && cd ..

Use the command line utility:

java -jar detekt/detekt-cli/build/libs/detekt-cli-[version]-all.jar --plugins detekt-hint/build/libs/detekt-hint-[version].jar --config detekt-hint/config/detekt.yml --classpath <your-classpath> --input <path-to-your-awesome-project>

For example:

java -jar detekt/detekt-cli/build/libs/detekt-cli-1.5.0-all.jar --plugins detekt-hint/build/libs/detekt-hint-0.0.2.jar --config detekt-hint/config/detekt.yml --classpath detekt-hint/ --input detekt-hint/

Remember to enter the latest detekt-cli version, the latest detekt-hint version and the path to your classpath and source code. Also, make sure that the detekt.yml you are using contains the unique package name in the configuration for the UseCompositionInsteadOfInheritance rule.

detekt-hint's Issues

Adding context to rules

Since many programming principles can be confusing and easily misinterpreted, i think adding some context in the comment could be helpful. In addition to giving a rule of thumb when to use composition over inheritance one could also print the public interface of the different classes.

Extract out the LCOM rule and create a PR in detekt repo for it

rename to detekt-hint

Snippet of githubaction is nt working

Hi :).
I try to make the plugin work with the danger bot but when i run the github action on PR, i have the following :

But i dont understand whats happening.
Thank you :)

Documentation with Dokka

Suggest possible rules to implement

Which rules should be implemented?

And how can we reduce the amount of false-positives with that rule?

Lage PR i andre repos for å promotere verktøyet (detekt feks)

Rule: Analysing LCOM value (Lack Of Cohesion of Methods) (Sign of Single Responsibility Principle violation)

https://blog.ndepend.com/lack-of-cohesion-methods/

Suggestion: Can report classes with low lcom and which methods with low cohesion, that are subject for refactoring.

Create issue on each rule and discuss it there.

Rule: Open/Closed Principle

https://www.tomdalling.com/blog/software-design/solid-class-design-the-open-closed-principle/

Looking for switch and enums could be a sign of violation. Look further into this and possible signs.

Kotlinc crash during github action running

I encountered this problem.
Everything run fine on PR but when the githubaction is running, kotlinc is crashing

�[0;0mExecuting kotlinc -script-templates systems.danger.kts.DangerFileScript -cp /usr/local/lib/danger/danger-kotlin.jar -script /Dangerfile.df.kts /tmp/danger-dsl.json danger_out.json - pid 374�[0;0m
Uncaught Kotlin exception: kotlin.Exception: Command kotlinc -script-templates systems.danger.kts.DangerFileScript -cp /usr/local/lib/danger/danger-kotlin.jar -script /Dangerfile.df.kts /tmp/danger-dsl.json danger_out.json exited with code 256
    at kfun:systems.danger.cmd.Cmd#exec(){} (0x228518)
    at kfun:systems.danger.cmd.dangerfile.DangerFile#execute(kotlin.String;kotlin.String){} (0x22915b)
    at kfun:systems.danger.DangerKotlin#run(){} (0x227408)
    at Init_and_run_start (0x22c005)
    at __libc_start_main (0x7ff97b9ceb97)
    at  (0x211029)
    at  ((nil))

set up test coverage report

test composition over inheritance

Test a case where the derived class is in another file than the parent.

Investigate inline comments on PR with the danger plugin.

Rule: Interface segregation principle

• chunky interfaces. needs threshold
• looking at implemented methods that are empty

ISP: Message: onClose is not implemented an may not be necessary. This is a possible violation of the interface segregation principle. Consider splitting up `null` into smaller interfaces with a single responsibility.

Seems to not support overridden/abstract functions from supertypes. This causes a "null" to be shown as name of interface, when really the class name shoud be shown.

Rule: Law of Demeter

Only talk to your friends!

make danger run on my own ruleset in addition to the normal detekt ruleset.

Should be able to follow he guide on detekt-website and modify the gradle task to build and include my .jar in the detekt run.

Create sample projects that only needs setup of Danger to work

• Kotlin project
• Android project

remove sample rules

Complete instructions on how to integrate with Danger in the readme

Suggest refactoring in LCOM rule

instead of adding images, create useful text.

Run ruleset on another project to see if it detects many violations

Rule: Command/Query separation (Methods should not return values and have side effects)

ISP: false-positive

override fun visitCondition(root: KtFile): Boolean = true

make the rules not failing the build.

The severity of the rules can be modified to let the build pass even detections has been found.

Delete samples folder, and instead create useful integration tests, or have a separate repo for testing.

Enable filtering

Figure out how to enable filtering such that only changed files are commented on.

Rule: Dependency Inversion

Improve usecompositioninsteadofinheritance and remove the config option and use bindingcontext to find package name

Create PR with integration of detekt-hint in detekt repo

add a configuration option to exclude certain classes in usecomposition.

Promote tool by writing a medium article about it

prepare for new release

Broken website header

https://mkohm.github.io/detekt-hint/

Get the base package name e.g io.github.mkohm in the UseComp rule and use that for checking.

If not available in the API it needs to be retrieved from the config.

update readme

Resolving problem related to lots of files reformatted

This resulted in a rate-abuse error from github. A max count of comments could maybe be applied to handle these issues. Ideally detecting what is formatting changes, and ignore warnings on that kind of code-changes.