Ignore empty directories for sources (#530)

Empty directories should not matter for source files, so let's ignore them for up-to-date checks as well. This avoids two issues: * Right now, the task will be out-of-date when you add an empty directory to the source folder. There will also be a build cache miss if the only difference between the sources is an empty directory somewhere. * In Gradle 8.0, the task won't skip any more if there are only empty directories in the source folder and no actual files. That is because the behaviour for skipping when empty and up-to-date checking will be more consistent.

Author: wolfs

src/main/groovy/com/google/protobuf/gradle/GenerateProtoTask.groovy

@@ -50,6 +50,7 @@ import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.provider.ProviderFactory
 import org.gradle.api.tasks.CacheableTask
+import org.gradle.api.tasks.IgnoreEmptyDirectories
 import org.gradle.api.tasks.Input
 import org.gradle.api.tasks.InputFiles
 import org.gradle.api.tasks.Internal
@@ -302,8 +303,9 @@ public abstract class GenerateProtoTask extends DefaultTask {
  }
 
  @SkipWhenEmpty
- @InputFiles
  @PathSensitive(PathSensitivity.RELATIVE)
+ @IgnoreEmptyDirectories
+ @InputFiles
  FileCollection getSourceFiles() {
  return sourceFiles
  }