Bestpractices

Composite Recipes

Recipes that include further recipes, often including the individual recipes below.

• Apply Kotlin best-practice idioms
• Apply Kotlin best-practice rewrites
• Collapse redundant collection / string conversions
• Find Boolean-conditional smells
• Find best-practice candidates
• Find class-declaration smells
• Find equality / comparison smells
• Find exception-handling smells
• Find function-declaration smells
• Find lambda / functional smells
• Find scope-function smells
• Find string-construction smells
• Find when-statement smells
• Use stdlib accessors for size / first

Recipes

• Drop redundant String.toString()
• Find !! inside a ?.let \{ \} body
• Find !x.isBlank() calls
• Find !x.isEmpty() calls
• Find !x.isNotBlank() calls
• Find !x.isNotEmpty() calls
• Find "" + x patterns
• Find .also \{ println(it) \} debug patterns
• Find === / !== referential-equality comparisons
• Find Throwable.printStackTrace() calls
• Find abstract class declarations without abstract members
• Find anonymous object : Interface \{ override fun … \} with a single override
• Find b == true / b == false comparisons
• Find chained !! assertions in a single expression
• Find class Foo : Any() declarations
• Find class Foo \{\} declarations with an empty body
• Find classes that could be data class
• Find classes with manual toString/equals/hashCode overrides
• Find classes with multiple overloaded secondary constructors
• Find data class declarations with var properties
• Find empty companion object declarations
• Find empty init \{ \} blocks
• Find forEach \{ it.toString() \} patterns
• Find forEach \{ println(it) \} patterns
• Find fun f(): Boolean = true|false literal-returning functions
• Find fun foo(): T \{ return x \} block bodies
• Find functions declared with : Nothing return type
• Find functions returning Pair<A, B>
• Find functions returning Triple<A, B, C>
• Find functions with explicit : Unit return type
• Find if (x != null) x.foo() patterns
• Find if (x == null) null else x.foo() patterns
• Find if (x) false else true patterns
• Find if (x) true else false patterns
• Find if (x) \{ return … \} else \{ … \} patterns
• Find lazy \{ \} calls without an explicit LazyThreadSafetyMode
• Find map \{ it.toString() \} / map \{ x -> x.toString() \} patterns
• Find marker object declarations that could be data object
• Find mutableListOf<T>().also \{ it.add(x) \} patterns
• Find mutableMapOf<K,V>().also \{ it.put(...) \} patterns
• Find mutableSetOf<T>().also \{ it.add(x) \} patterns
• Find named companion object Constants patterns
• Find object declarations with var properties
• Find open class declarations without overridable members
• Find return Unit / return kotlin.Unit statements
• Find run \{ \} calls with an empty body
• Find sealed class declarations that could be sealed interface
• Find suspend fun declarations returning Job / Deferred
• Find throw Exception("…") calls
• Find throw RuntimeException("…") calls
• Find top-level run \{ … \} whose body never uses this
• Find trivial String.format("%s", x) calls
• Find try \{ … \} catch (e: Exception) \{ null \} patterns
• Find when (b: Boolean) selectors
• Find when (x) expressions without an else branch
• Find when (x) \{ A -> … \} with a single branch
• Find when (x) \{ … \} used as a statement
• Find when with two or more branches having identical bodies
• Find wildcard import a.b.* statements
• Find x + "" patterns
• Find x.also \{ \} calls with an empty body
• Find x.compareTo(y) <op> 0 patterns
• Find x.isNotEmpty() on String where isNotBlank() might be wanted
• Find xs.forEach \{ ys.add(it) \} patterns
• Find xs.toList().forEach \{ … \} patterns
• Use distinct() instead of toSet().toList()
• Use first() instead of get(0)
• Use length instead of String.count()
• Use size instead of Collection.count()
• Use toList() instead of toMutableList().toList()
• Use toSet() instead of distinct().toSet()
• Use toSet() instead of toList().toSet()
• Use toTypedArray() instead of toList().toTypedArray()
• Use trim() instead of trimEnd().trimStart()
• Use trim() instead of trimStart().trimEnd()