AnnotationOnSeparateLine false positive

[p-dmitriy]

Room has @MapColumn that can be used to specify column that should be used as map key. AnnotationOnSeparateLine triggers for such code, and in my opinion it's false positive, because there is only one annotation for the type, which is allowed by the rule description.

Steps to Reproduce

@Query("*SQL here*")
abstract fun getEntities(): Map<@MapColumn(columnName = "Id") Long, Entity>

Your Environment

• Version of ktlint used: ktlint-ruleset-standart 0.50.0 through detekt 1.23.7
• Android Gradle Plugin: 8.7.0
• Room: 2.6.1
• Version of Gradle used (if applicable): 8.10.2
• Operating System and version: macOS 15.1

[paul-dingemans]

I see where you're coming from. The way how to write this construct is however a library specific preference. Ktlint can/will not make exceptions for specific library annotations.

But I can see that this is a construct that might be heavily used in certain classes, which would lead to reduced readability. Best I can do, is to consider a configuration option in which you can list the annotations that should be ignored from this rule.

Or you can just simply disable the rule entirely. See https://pinterest.github.io/ktlint/latest/faq/#how-do-i-enable-or-disable-a-rule

[p-dmitriy]

As far as I see now rule doesn't follow own description. From the rule description:

Multiple annotations should be on a separate line than the annotated declaration

In my case there is single annotation (@MapColumn) for Type annotation target. @Query annotation belongs to Function target. So not first annotation nor second violates rule.
For example: if I add annotation to the function parameter this not violate the rule too. Underlying logic as I can imagine the same: different annotation targets Function and Parameter.
I'd not want to disable this rule, because it helpful, all I want is make this rule more consistent.

[paul-dingemans]

LOL. If you take quotes from the docs, you might better want to include the full quote:

Multiple annotations should be on a separate line than the annotated declaration; annotations with parameters should each be on separate lines; annotations should be followed by a space

@MapColumn(columnName = "Id") has a parameter columnName and therefore is forced to be written on a separate line.

Disabling the rule is how you can move forward at this moment, without being bothered by the formatting. Once the rule is made configurable, you can re-enable the rule and add this annotation to the exclude list.