Running ktlintFormat twice deletes files

[donaldchen]

Steps to reproduce the bug

1. Use ktlint-gradle version 9.1.0 and ktlint version 0.35.0 with the following configuration:

ktlint {
    version = "0.35.0"
    debug = true
    verbose = true
    android = true
    outputToConsole = true
    outputColorName = "RED"
    enableExperimentalRules = false
}

2. Run ./gradlew ktlintFormat --continue once. (Then run git status, and observe that the auto-formatted files were modified)
3. Run ./gradlew ktlintFormat --continue a second time

Expected Behavior
Running ./gradlew ktlintFormat --continue the second time should not making any additional changes. The previously modified files should still show up as modified in git status, and no files should be deleted.

Actual Behavior
All the files that were previously marked as modified are now deleted (observed via git status).

I also tried the gradle integration recommended in https://github.com/pinterest/ktlint without plugins, and running the non-plugin ktlintFormat task multiple times did not delete any files. This makes me suspect that the bug is in ktlint-gradle.

[Tapchicoma]

Thank you for the report, I've successfully reproduced it 🤔

[Tapchicoma]

Most probably 9.0.0 version does not have such problem, as the issue in incremental task support.

[donaldchen]

@Tapchicoma , thanks for the suggestion! I tried version 9.0.0 for ktlint-gradle, and I can confirm that the files no longer get deleted when I run ./gradlew ktlinFormat --continue multiple times.

[wolfs]

Gradle currently doesn't support tasks which have the input as the output very well (if at all). Can you add the incremental support only to the lint task and not the format task?

[Tapchicoma]

That is my plan I want to do tomorrow...