Ktlint experimental rules are never applied in gradle plugin

[dhoepelman]

ktlint experimental rules are supported since #1168 .
While configuration is available, neither it nor the right .editorconfig entry seem to have any effect.

A repository showing a minimal reproducing example of the problem can be found here.

Given this config:

spotless {
    kotlin {
        target("**/*.kt", "**/*.kts")
        ktlint("0.48.2")
            .setUseExperimental(true)
            .setEditorConfigPath("$rootDir/.editorconfig")
    }
}

(I also tried some variations of the above, but it doesn't matter)

and a file Test.kt:

val triggersExperimentalRule = false

Running ./gradlew spotlessCheck --stacktrace will be successful:

$ ./gradlew spotlessCheck --stacktrace

BUILD SUCCESSFUL in 403ms
3 actionable tasks: 2 executed, 1 up-to-date

while ktlint fails:

$ ktlint
10:29:33.192 [main] INFO com.pinterest.ktlint.internal.KtlintCommandLine - Enable default patterns [**/*.kt, **/*.kts]
[...]/bug-spotless-ktlint-experimental-rules/src/main/kotlin/Test.kt:1:5: Property name should use the screaming snake case notation when the value can not be changed (cannot be auto-corrected) (experimental:property-naming)

Summary error count (descending) by rule:
  experimental:property-naming: 2

• summary of problem
• gradle or maven version: 8.0.2 or 7.6
• spotless version: 6.17.0
• operating system and version: OS X 13.2.1
• copy-paste your full Spotless configuration block(s), and a link to a public git repo that reproduces the problem if possible
• copy-paste the full content of any console errors emitted by gradlew spotless[Apply/Check] --stacktrace

[dhoepelman]

This might be 0.48+ specific, they have changed the API in 0.48. Additional context. If I have time I may investigate.

Another thing from the 0.48.2 release notes it seems that ktlint want to discourage config like setUseExperimental and let .editorconfig be the source of truth.

[dhoepelman]

This specific bug is likely irrelevant since spotless 0.6.20, as this mentioned the behavior changing in the changelo
https://github.com/diffplug/spotless/blob/main/plugin-gradle/CHANGES.md#6200---2023-07-17