Function joins_author_topic 

pub(crate) fn joins_author_topic(
    tags: &[String],
    default_page: Option<&str>,
) -> bool

Whether the author’s tags put the block on a topic other than default_page: @describeIn topic ..., or an @rdname topic that names another page. The block then joins a topic whose own block (usually the author’s, often in R) documents the page, so generated lines that claim the page (a structural @param, the page \name and title) must give way to it.

tags must be the author’s own tags (doc comment or doc = "..."), and default_page the page the framework puts the block on anyway: a class generator passes the class name, so a redundant author @rdname <Class> counts as no page tag. A standalone function passes None (whether an @rdname names its own page or its file’s stem page is only known when the wrapper registry writes the file), so any @rdname counts there.