Is it possible to determine if an annotation value...

# ksp

[jameskleeh]

Is it possible to determine if an annotation value is present because it was the default or if it was set manually?

[Grégory Lureau]

How is it possible to set an annotation by "default"? What does that mean?

[Jiaxiang]

I think it means when you define an annotation class, you can specify a default value for the annotation value arguments.

[jameskleeh]

Correct

[jameskleeh]

In Micronaut we support the notion of an argument that is actually set vs a default value

[jameskleeh]

I’ve determined the likely way to determine this is through the constructor of the annotation, however I don’t know how to get the default values from the parameters. Any ideas @Jiaxiang?

[Jiaxiang]

I can think of it, but what is the usage of that? I feel like you have all you need with getting the value itself, it shouldn’t matter whether it comes from a default value or defined in the code?

[jameskleeh]

its more efficient to store the default values from annotations once instead of each time they are used

[jameskleeh]

so its split out that way to reduce memory usage

[jameskleeh]

Micronaut stores annotation data in our own API that is accessible at runtime so no runtime reflection is necessary to retrieve that info

[Jiaxiang]

to store it I will need a flag in KSP to determine if a value is present in code, or alternatively do a computation every time user query it, either sacrifices space or time efficiency in my opinion.

[Jiaxiang]

also we don’t actually do runtime reflection to get the annotation value, if reflection is your concern.

[jameskleeh]

reflection is a concern for us at runtime, not compile time

[jameskleeh]

So are you saying that it isn’t possible with the current version of KSP?

[Jiaxiang]

it isn’t possible in current version, I can see it is doable but need more context on the necessity of this use case.

[jameskleeh]

A boolean on KSValueArgument isDefaultValue or something of the sort would be sufficient I believe

[jameskleeh]

perhaps not actually

[Jiaxiang]

I would call it isPresent since user can still write a value equal to default value, and I think you are more interested in if user has written the value or not, rather than the actual value

[jameskleeh]

I’ll create an issue

[jameskleeh]

https://github.com/google/ksp/issues/674