agustarc

// Bad
fun foo() = foo("a")
fun foo(a: String) { ... }

// Good
fun foo(a: String = "a") { ... }   

agustarc

// Bad: use of mutable collection type for value which will not be mutated
fun validateValue(actualValue: String, allowedValues: HashSet<String>) { ... }

// Good: immutable collection type used instead
fun validateValue(actualValue: String, allowedValues: Set<String>) { ... }

// Bad: arrayListOf() returns ArrayList<T>, which is a mutable collection type
val allowedValues = arrayListOf("a", "b", "c")

// Good: listOf() returns List<T>

agustarc

// Avoid doing this:

/**
 * Returns the absolute value of the given number.
 * @param number The number to return the absolute value for.
 * @return The absolute value.
 */
fun abs(number: Int) = ...

// Do this instead:

agustarc

foo {
   context: Context,
   environment: Env
   ->
   context.configureEnv(environment)
}    

agustarc

appendCommaSeparated(properties) { prop ->
    val propertyValue = prop.get(obj)  // ...
}   

agustarc

fun foo() {
    ints.forEach lit@{
        // ...
    }
}    

agustarc

list.filter { it > 10 }

agustarc

drawSquare(
    x = 10, y = 10,
    width = 100, height = 100,
    fill = true
)    

agustarc

when (foo) {
    true -> bar() // good
    false -> { baz() } // bad
}   

agustarc

private fun parsePropertyValue(propName: String, token: Token) {
    when (token) {
        is Token.ValueToken ->
            callback.visitValue(propName, token.value)

        Token.LBRACE -> { // ...
        }
    }
}