The reason I didn’t use String.to_existing_atom/1 is that it requires some code to have executed to create that atom. There are some situations where the atom may not exist yet, but will eventually. I check the resulting strings with field in @order_by_fields, so that I know those functions could only ever create two new atoms from user input.
EDIT:
iex(1)> String.to_existing_atom("foo")
** (ArgumentError) argument error
:erlang.binary_to_existing_atom("foo", :utf8)
iex(1)> :foo
:foo
iex(2)> String.to_existing_atom("foo")
:foo
