Support lint and formatting of annotations

[jaredsburrows]

Description:

• ktlint should find annotations with no arguments not on the same line
• ktformat should format them by putting them on the new line

References:

• https://android.github.io/kotlin-guides/style.html#annotations

[AleksandrSl]

@jaredsburrows, @shyiko
Based on https://android.github.io/kotlin-guides/style.html#annotations
https://kotlinlang.org/docs/reference/coding-conventions.html#annotation-formatting
there is only one rule. Annotations with arguments must be on separate lines and even this is not enforced:

Annotations are typically placed on separate lines

[cable729]

@AleksandrSl I read it a little differently, as in the quote you posted is an general rule that serves as an intro to the section, and the following rules describe exactly when they should be placed on separate lines. I.e. the following is valid:

@JvmField var disposable: Disposable? = null
@JvmField @Volatile
var disposable: Disposable? = null
@MyAnnotation("asdf")
var disposable: Disposable? = null

But this is not:

@JvmField @Volatile var disposable: Disposable? = null
@MyAnnotation("asdf") var disposable: Disposable? = null

[cable729]

Anyone else working on this? Mind if I take this one?

[shyiko]

@cable729 that would be great!