nixos/types: cast path type to string, when it is "path"
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This handles a specific case, when "path" type was supplied to `types.path` option. Previously it was converted into store path, because it was used in other derivations: ``` nix-repl> builtins.toJSON /etc/nixos/configuration.nix "\"/nix/store/wd12lm99vp1syi3ywala46w4zhnvk83z-configuration.nix\"" ``` So making `users.users.alice.home = /home/alice;` would convert `/home/alice` directory into store path. I can't think of situation when this is what is expected. State dirs and password files could have been converted into store paths as well. Having state dir on ro mount would probably result into error, but password files were simple enough, so could easily be copied into `/nix/store` and nobody noticed. On other hand, we can't cast `types.path` to string always, because in many places package is provided instead of path. It worked because of silent casts... I'll leave a TODO for future contributors. Reported in https://discourse.nixos.org/t/re-use-existing-home-migrating-from-ubuntu/2353
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This pull request has been mentioned on Nix community. There might be relevant details there: https://discourse.nixos.org/t/re-use-existing-home-migrating-from-ubuntu/2353/5 |
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This isn't desirable in the general case, as importing the path into the store has a key benefit: making it part of the system closure. Not copying paths will make e.g. rollbacks a lot less effective. |
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Alright, agree. |
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More principled approach to this is coming #78640 |
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Motivation for this change
This handles a specific case, when "path" type was supplied to
types.pathoption. Previously it was converted into store path, because it was used
in other derivations:
So making
users.users.alice.home = /home/alice;would convert/home/alicedirectory into store path.
I can't think of situation when this is what is expected. State dirs and
password files could have been converted into store paths as well.
Having state dir on ro mount would probably result into error, but
password files were simple enough, so could easily be copied into
/nix/storeand nobody noticed.On other hand, we can't cast
types.pathto string always, becausein many places package is provided instead of path. It worked because of
silent casts... I'll leave a TODO for future contributors.
Reported in https://discourse.nixos.org/t/re-use-existing-home-migrating-from-ubuntu/2353
PS. I don't know how to write automated test for this, because it involves "paths", which are awkward to work with in a reproducible manner. I've tested locally with a local "path".
Things done
sandboxinnix.confon non-NixOS)nix-shell -p nox --run "nox-review wip"./result/bin/)nix path-info -Sbefore and after)