Project build directory is not excluded when multiple targets are specified

[bigdaz]

The FormatExtension.parseTargetIsExclude() method provides special handling to exclude .git, .gradle and project build output directory from processing, when the target matches the pattern **/*.... This works well to avoid adding a bunch of spurious files to the Spotless inputs.

Unfortunately, this handling is limited to the case where a single target is specified. So if a formatter is configured with target('**/*.kt', '**/*.kts') then the project build output is not excluded from the inputs.

In Gradle versions < 7.0, this is inefficient but does not result in any user errors/warnings.
In Gradle 7.0, this is more problematic: the build output directory is effectively an input to the Spotless task, resulting in a warning like this:

> Task :app:spotlessKotlinGradle
Execution optimizations have been disabled for task ':app:spotlessKotlinGradle' to ensure correctness due to the following reasons:
  - Gradle detected a problem with the following location: '/Users/foo/XXX-Android/app'.
     Reason: Task ':app:spotlessKotlinGradle' uses this output of task ':app:spotlessJava' without declaring an explicit or implicit dependency. 
     This can lead to incorrect results being produced, depending on what order the tasks are executed. 
     Please refer to https://docs.gradle.org/7.0-rc-2/userguide/validation_problems.html#implicit_dependency for more details about this problem.

To reproduce this issue:

• Clone this repository: https://github.com/bigdaz/spotless-835
• Execute ./gradlew clean spotlessCheck

Here is a build scan that results from this execution: https://scans.gradle.com/s/zw2f7glrsko7s/deprecations. Note that this does not include the "Execution optimizations have been disabled" message, but this shows on the console.

[bigdaz]

@nedtwigg I am willing to contribute a fix for this issue, but I'm not quite sure what behaviour is desired. I think excluding the .git and .gradle directories almost always makes sense, and excluding the build output directory makes sense in the majority of cases. I'm thinking something like:

1. If no target starts with .git/ then we ignore the .git directory
2. If no target starts with .gradle/ then we ignore the .gradle directory
3. If no target explicitly includes the build output directory, then we exclude this directory.

There's still the case like target('**/*.java', 'build/generated-src/*.scala'), where the project output directory would not be excluded. Hopefully we can find a way to exclude all of build except for the explicit include. Let's see.

Thoughts?

[nedtwigg]

I like your fix, but I think there is a simpler fix which works iff FileCollection.plus/minus is hierarchical:

• handle target(List<Sting> by creating a FileCollection per string, with the existing logic we have right now
• union them together at the end

Basically do a more strict "map reduce" with map String -> FileCollection, reduce FileCollection::plus.

Does ('**/*.java' minus 'build/**') plus 'build/generated-src/*.scala' respect the parentheses? Or does it end up as '**/*.java' plus 'build/generates-src/*.scala' minus 'build/**' === '**/*.java' minus 'build/**'?

[bigdaz]

I like that simpler plan. I'm pretty sure that each file collection in a union has it's own set of includes and excludes, and I'll confirm how this interacts with the new "implicit dependency check" feature in Gradle 7.

[nedtwigg]

Released in plugin-maven 2.10.0 and plugin-gradle 5.12.0.