For example
flysystem:
storages:
default.storage:
adapter: 'local'
options:
directory: '%kernel.project_dir%/var/storage/default'
flysystem+default.storage://foo/bar/bat.csv points to %kernel.project_dir%/var/storage/default/foo/bar/bar/csv.
Similar to https://github.com/twistor/flysystem-stream-wrapper, but up to date.
This wrapper works with recent Flysystem: https://github.com/m2mtech/flysystem-stream-wrapper
Thinking about it further, it seems like a thing which could be opted-in per filesystem, something like
flysystem:
storages:
some.storage:
adapter: 'asyncaws'
stream_wrapper: true