Why there are no pre-defined rules?

Many linters including Detekt and ktlint have a predefined set of rules. These rules are derived and aligned with guidelines or common practices for writing high-quality code and industry coding conventions (Kotlin coding conventions, Android Kotlin style guide, etc.).

However, there are no industry standards when comes to application architecture. Every code base is different - different class names, different package structures, different application layers, etc. As the project grows code base evolves as well - it tends to have more layers, more modules, and a more complex code structure. These "rules" are hard to capture by generic linter, because they are often specific to the given project.

Let's consider a use case - a concept defined by the Clean Architecture. At a high level the use case definition is quite simple - "use case holds a business logic". How the use case is represented in the code base? Well... In one project this may be a class that has a name ending with UseCase, in another, it may be a class extending BaseUseCase and in another class annotated with @UseCase annotation. The logic for filtering "all project use cases" will vary from project to project.

Now let's consider the actual structure of the use case class:

  • should every use case have UseCase a suffix in the class name?

  • can the use case be extended or include another use case?

  • should every use case reside in usecase the package?

  • should the use case have a single method?

  • how this method should be named?

  • can this method have overloads or should it be defined as invoke an operator?

  • should this method have a suspended modifier?

Answers will vary from project to project. That is why Konsist favors a more flexible approach - it allows filtering members and defining custom code base assertions (tests). On top of that Konsist is utilizing Kotlin collection processing API to provide more control over filtering and asserting declarations (Declaration).

Some things can be standardized across different projects e.g. constructor parameter names being derived from the property name, or alphabetic order of the parameter. For now, custom tests will be a core part of Konsist, however, we are considering the addition of a small set of predefined rules in the future.

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