Re: Cosmic Progress

[colbyt <colby@colbyt.com>]

Following up on the read-only config question from earlier in this
thread: you were right — my July 7 message conflated two things.

cosmic-config never requires XDG_CONFIG_HOME to be writable. The only write in Config::new is a create_dir_all on $XDG_CONFIG_HOME/cosmic/<AppID>/v<N>, which is a no-op when the
directory already exists. With the empty per-component directories
pre-seeded on a read-only mount, Config::new succeeds, reads behave
identically to a writable setup, and writes fail with a plain Err
rather than a panic. The panic we saw was create_dir_all returning
EROFS when those directories were *absent*, unwrapped by the caller
(cosmic-comp 1.2.0, src/config/mod.rs:172).

Verified with a minimal harness against cosmic-config at the libcosmic rev cosmic-comp 1.2.0 pins (0bb006c5) and against current master (dc1cf9f0) — same behavior on both, with the read-only mount
both as a bwrap ro-bind (real EROFS) and as chmod 555.

Two details from that may be useful for the empty-dir seeding in your cosmic-comp series:

1. Seeding a bare cosmic/ isn't enough — the full
   cosmic/<AppID>/v<N> path has to exist for every component/version pair the session constructs, or that component's Config::new fails the same way.
2. Config::new_state does the identical create_dir_all under
   XDG_STATE_HOME, so state directories want the same seeding as
   config.