Does kapt support incremental builds?

# build-tools

[Eugen Martynov]

Does kapt support incremental builds?

[gildor]

Annotation Processing is not incremental, not only with Kapt. Same sitation with apt and Java.
Kapt have some incremental steps (like stubs generation), but in general AP is not incremental

[gildor]

There is a project from Gradle and Google that wants to priovide api for AP authors to support incremental annotation processing
https://github.com/gradle/incap
Detailed description of Milestone 1
https://docs.google.com/document/d/1CXNfKmPx9hqfnGWic3F9sKHQ6T8ImDVxnXfkvWYqwxg/edit

[gildor]

Under the hood AP still can have own incremental code generation, but without integration with build system it’s hard to support and it’s not flexible enough

[Eugen Martynov]

I completely missed that annotation processing is not incremental with gradle https://github.com/gradle/gradle/issues/1320

[Eugen Martynov]

Thanks for pointing out

[gildor]

Not only with Gradle. Java JSR-269 provides nothing for support of incremental AP, so it’s completely build system feature that should be integrated to AP library.

[Eugen Martynov]

ok, so I consider annotation processing an developer evil 🙂

[gildor]

The Good, the Bad and the Ugly 🙂

[Eugen Martynov]

Why it was never on the radar? AP is standard since java6

[gildor]

I suppose nobody used this so intensive as today.

[gildor]

also java compilation was not incremental (it’s build tools feature, not javac itself)

[gildor]

Also I think Android developers pushed that a lot, because AP is super popular on Android because of many reasons

[Eugen Martynov]

Thanks!

[Eugen Martynov]

Thanks for the discussion and pointing out to the problem and reference for the solution

[gildor]

No solution yet unfortunately but I want to believe 👽

[Eugen Martynov]

https://github.com/wangwh03/NewYorkTimes/tree/master/app

[Eugen Martynov]

Looks like we can already try something

[gildor]

Yes, it’s proof of concept. Problem that to achieve incremental AP all your AP should support that. In my Android case two biggest thing is Databinding and Dagger

[Eugen Martynov]

We also use them, but at least Butterknife and autovalue are incremental

[Eugen Martynov]

so some small gain in build speed

[Eugen Martynov]

or it will re-run everything in this case?

[gildor]

you should get some gain I suppose, just because AP generates less code, but think it’s minor part, biggest one is incremental java/kotlin compilation that cannot be achieved without incremental AP

[Eugen Martynov]

Ok, I need to read how incremental java compilation in gradle is implemented

[Eugen Martynov]

I was thinking it can detect what file is changed

[Eugen Martynov]

so if less files are re-generated then less compile time is needed

[gildor]

Java incremental compilation disabled if you have AP

[stepango]

Only way of getting incremental AP is breaking app into small modules, since AP would be running only inside changed module build speed would be much faster👍

[gildor]

@stepango Unfortunately doesn’t work with Dagger Subcomponents and Data Bindings
And it’s not incremental, but yeah, at least you can compile only one module and modules that use it

[gildor]

btw Incap Milestone 1 already have PR to Gradle - https://github.com/gradle/gradle/pull/3434