package bonsai

Functions that take bonsai values that contain t, and kicking off reads whenever those values change.

The arguments here are chosen to match the results from Bonsai_web_ui_form.Elements.File_picker. So you can do things like:

let%sub file_picker =
  Bonsai_web_ui_form.Elements.File_picker.create [%here] ()
in
let%sub current_file =
  Bonsai_web_ui_file.Read_on_change file_picker
in
match%sub current_file with
| Starting | In_progress _ -> Bonsai.const "file still loading"
| Complete (Error e) -> Bonsai.read (e >>| Error.to_string_hum)
| Complete (Ok (_filename, contents)) -> Bonsai.read contents

NOTE: these computations are not safe for use in Tangle as internally they require a model which cannot be of_sexp'd.