I'd like to be able to have a set of fixers that run on save that is separate from the fixers that run with :ALEFix.

For example, I universally want to have the remove_trailing_lines and trim_whitespace fixers to run when I save a file, but I do not always want to run the rustfmt fixer when I save (some projects don't use it and I don't want to reformat lots of code that isn't my own).

" `ale_fixers` is a superset of `ale_fixers_on_save` and contains those listed in `ale_fixers_on_save`.
let g:ale_fixers = {
\   'rust': [ 'rustfmt' ],
\ }
let g:ale_fixers_on_save = {
\   '*': [ 'remove_trailing_lines', 'trim_whitespace' ],
\ }

This would enable me to always have trailing lines removed and whitespace trimmed without needing to remember to do that, but gives me the option of triggering rustfmt manually through ALE on my own projects with my binding to :ALEFix.