Entry <xxx> is a duplicate but no duplicate handling strategy has been set

[alesproch]

It's not possible to set duplicatesStrategy for copying of dependencies into lib folder for createExe/launch4j task.
Using gradle 7.x

[TheBoegl]

could you please provide a simple working example that you expected to work

[Shadow-Devil]

Hi, today I faced the same issue.
My minimal build.gradle looks like this:

plugins {
    id 'java'
    id 'edu.sc.seis.launch4j' version '2.4.6'
}

dependencies {
    implementation 'org.glassfish.jaxb:jaxb-runtime:3.0.2'
    implementation 'com.sun.xml.bind:jaxb-xjc:3.0.2'
}

Both dependencies include a common dependency jaxb-core-3.0.2.jar.

The Error that is being displayed is:

Entry jaxb-core-3.0.2.jar is a duplicate but no duplicate handling strategy has been set. 
Please refer to https://docs.gradle.org/7.1.1/dsl/org.gradle.api.tasks.Copy.html#org.gradle.api.tasks.Copy:duplicatesStrategy for details.

But when I try to add a duplication handling strategy it doesn't work:

plugins {
    id 'java'
    id 'edu.sc.seis.launch4j' version '2.4.6'
}

dependencies {
    implementation 'org.glassfish.jaxb:jaxb-runtime:3.0.2'
    implementation 'com.sun.xml.bind:jaxb-xjc:3.0.2'
}

launch4j {
    duplicatesStrategy = DuplicatesStrategy.INCLUDE
}

This works inside the jar task.

[Shadow-Devil]

If you could help me with some guidance where the error could be solved, I would like to work on this issue 😄

[TheBoegl]

This seems to be related to the used copy tasks. You should be able to create a PR adding the strategy there and testing it with the reproducible code snippet you provided.

[Shadow-Devil]

So I've created a test with my code snippet and it worked.
It's because this repo is using Gradle 6.x and I was using Gradle 7.x.
See also here: https://docs.gradle.org/current/userguide/upgrading_version_6.html#duplicates-strategy

[Shadow-Devil]

Is it currently possible to let a test run with a different Gradle version than specified at the root project?

[Shadow-Devil]

I thought, that maybe something like this would work:

launch4j{
    mainClassName = 'com.test.app.Main'
    copyConfigurable = copySpec {
        duplicatesStrategy = DuplicatesStrategy.INCLUDE
    }
}

But now I'm getting the error message:

Cannot fingerprint input property 'copyConfigurable': value 'org.gradle.api.internal.file.copy.DefaultCopySpec_Decorated@5fd1326f' cannot be serialized.

I was looking through the code and found the copyConfigurable, that to my understanding should also be settable to a CopySpec.

[TheBoegl]

There are already some tests in this repo that run against different gradle versions.

I don't have access to my IDE now but you might be able to set the strategy on the distSpec variable.

[Shadow-Devil]

I've created a draft PR (#123) that fixes the issue. It just hardcodes it to exclude any duplicate entries. Maybe we should introduce a new property so the user can specify what DuplicatesStrategy should be used.

[Shadow-Devil]

I think this issue can be closed, since the PR was already merged