Explain Gradle + Vavr custom pattern ($Patterns/$Unapply)

[sir4ur0n]

When using Vavr with $Patterns / $Unapply, one must add additional configuration to its dependencies, otherwise Gradle does not process annotations by default.

This would be nice to mention this in the documentation.

It seems that annotationProcessor("io.vavr", "vavr-match-processor", vavrVersion) does the trick.

[danieldietrich]

Thanks for the hint, will do!

Do you have (a minimal) Gradle config that I can take as example?

[sir4ur0n]

plugins {
    java
}

group = "com.sir4ur0n.github"
version = "1.0-SNAPSHOT"

repositories {
    mavenCentral()
}

dependencies {
    val vavrVersion = "0.10.0"
    // Provides @Patterns, @Unapply, Tuple0..8
    implementation("io.vavr", "vavr", vavrVersion)
    // Processes patterns during compilation, outputs them in build/classes by default
    annotationProcessor("io.vavr", "vavr-match-processor", vavrVersion)
}

configure<JavaPluginConvention> {
    sourceCompatibility = JavaVersion.VERSION_1_8
    targetCompatibility = JavaVersion.VERSION_1_8
}

[danieldietrich]

@Sir4ur0n thank you, that helps! I think there also needs to be the additional dependency

compileOnly("io.vavr", "vavr-match", vavrVersion)

[sir4ur0n]

Not needed explicitly, it's a transitive dependency of io.vavr:vavr. Anyway you also need io.vavr:vavr tu build patterns using Tuple0..8.

[danieldietrich]

I see. That is interesting because vavr-match should only be a compile time dependency of Vavr. I think the dependency 'leaked' into the library with the PR #2294.

I need to fix that in the next version.

[nfekete]

compile is the default scope in maven if no scope is specified. <scope>compile</scope> thus should be redundant. See maven docs.

[danieldietrich]

Sorry, I confused Maven’s compile with Gradle’s compileOnly. What I meant was that we might need s.th. like Maven’s provided in order not to leak vavr-match as transitive dependency.

See https://blog.gradle.org/introducing-compile-only-dependencies

The important parts:

[Opalo]

@Sir4ur0n do you have a working example of using pattern matching with annotation processor with gradle? I've added a dependency but still cannot compile it.

[sir4ur0n]

I haven't developed in Java in many years, I won't be able to help you :sweat_smile:

[Opalo]

Ok, thanks. Managed to do that on my own ;)

[Opalo]

Here is my answer to the question that I was working on.