Ktlint Guide

Table of Contents

• Installation
• Commands
• Macros
  • Steps to create a macro
• How to fix the most common issues?

Installation

Once you have completed all the installation steps, you will have a ktlint file in your opensource/oppia-android-tools folder.

Commands

Note: Keep your terminal or command line to opensource/oppia-android path while running below commands.

• Check the version of your ktlint. As of now on GitHub Actions, we are using 0.37.1.
  ../oppia-android-tools/ktlint --version
  

• Android Kotlin Style Guide using --android
../oppia-android-tools/ktlint --android "path/of/your/kotlin/file"

  • Examples
    
    • Specific File
      ../oppia-android-tools/ktlint --android app/src/sharedTest/java/org/oppia/android/app/walkthrough/WalkthroughWelcomeFragmentTest.kt
      
    • Specific Directory
      ../oppia-android-tools/ktlint --android "utility/src/**/*.kt"

• Android Kotlin Style Guide using --android with Ktlint Auto Formatter -F. This will fix some of the issues automatically.
  ../oppia-android-tools/ktlint -F --android "path/of/your/kotlin/file"

  • Examples
    
    • Specific File
      ../oppia-android-tools/ktlint -F --android app/src/sharedTest/java/org/oppia/android/app/walkthrough/WalkthroughWelcomeFragmentTest.kt
      
    • Specific Directory
      ../oppia-android-tools/ktlint -F --android "utility/src/**/*.kt"

Macros

In Android Studio we have a feature called Macros which helps you convert multiple tasks in one shortcut.

There are two major tasks when we talk about style formatting, One is the Reformat Code and another one is Optimize imports.

• Reformat Code - this will reformat your code with proper indentation and newlines wherever needed.
• Optimize imports - this will remove all the unused import from your file. Also, this will rearrange your imports in lexicographical order and all those imports which are starting with java, javax or Kotlin will get shifted at the end of the import list which is a correct order.

Steps to create a macro:

1. Double shift
2. Search for "macros"
3. Click on "Macros"
4. Click on "start macro reading"
5. Menu Toolbar -> Code -> Reformat Code -> Menu Toolbar -> Code -> Optimize Import -> click on stop macro reading at bottom
6. Now you can give whatever shortcut you want and these above two steps will get performed

How to fix the most common issues?

• Wildcard Imports - If you had imported anything which directs to just the package import java.util.*, it will give you an error saying there should not be any wildcard imports. So, you had to use the path completely for what you need in your file.

  • Example - import java.util.Date or import java.util.Locale

• Exceeding 100 char limit - This means that there is a line of code which is more than 100 char in one line. You must have noticed a grey line in the editor area, the code should not cross that line.

  There are some cases like the name of the tests where the code crosses that line and we cannot rearrange it as it is the name of the function. This does not apply to comments. There you should put a ktlint comment using which ktlint disable the check for 100 char limit. // ktlint-disable max-line-length

  • Example -
    
    • fun testWalkthroughWelcomeFragment_recyclerViewIndex1_topicSelected_clickNoButton_worksCorrectly() { // ktlint-disable max-line-length

Note: We don't recommend the use of // ktlint-disable max-line-length to disable the ktlint check unless the line of code cannot be broken into multiple lines to prevent disabling ktlint check.