IssueTracker

One additional comment that would improve usability of working with custom source sets:

The source sets created by default don't require the directories to exist. That is src/free/my_type will be used for input when it exists, but if it doesn't then it's safely ignored.

However, when using the addStaticSourceDirectory API to register your own directory, a check is performed and IllegalArgumentException is thrown when the directory doesn't exist already, requiring something like:

        try {
            variant.sources.getByName(SOURCE_TYPE)
                .addStaticSourceDirectory(
                    project
                        .layout
                        .projectDirectory
                        .dir("src/${variant.name}/google-services").toString()
                )
        } catch (e: IllegalArgumentException) {
            // directory doesn't exist, ignore
        }

Perhaps it would be OK to remove this check and let plugins register directories that can potentially contain sources, but not do a hard failure if they don't exist?

I sent two CLs for these, PTAL when you have some time :)

ADNVN 11

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