setting max_size on dcc.Upload does not restrict users

[afultonuq]

Bug

Setting max_size on the dcc.Upload component does not restrict users from selecting a file over the max_size limit.

Rather, the max_size seems to restrict the component from triggering a callback (either through filename or contents inputs). This makes it very difficult to provide user feedback on the file being too large.

Expected behavior

A file over the max_size limit should not be selectable, or should still trigger the callback, perhaps with contents = None?

[faulty13]

Related community forum discussion: https://community.plotly.com/t/dcc-upload-max-size-exceeded-notification/