Function is_data_file 

pub fn is_data_file(path: &Path) -> bool

Whether a path looks like something datui can open.

Its name, or its place: a part file with no extension inside a .parquet directory is Parquet, as Spark and GBIF write them. Every route that asks what a name means asks here — the listing, the search, ~ input, the counts and the schema pane — because the one that did not was always the one that disagreed.