nixos/nix-daemon: Fix merging order for substituters option #159662
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The `substituters` option in `nix.settings` uses the order of the substituters listed to define priority. Prior to #139075, the corresponding option `binaryCaches` is declared in the `nix` namespace, which is guaranteed to be merged last. However, the order of merging isn't guaranteed in submodules. This cause definitions to be appended to the default value instead of prepended, breaking backwards compatibility as reported in #158356. The way this is addressed in the module system is with order priorities via `mkOrder` and sorting definitions before merging. This PR restores the previous behavior by setting a higher priority to the substituters option defined internally, thus all definitions with default priority will be merged before it. This was chosen because the `mkRenamedOption` function does not preserve order priority so users using legacy options do not have precise control on placement. This change should suffice for simple configuration, but further revision to the module system is needed for to make various `mk*` functions aware of order priorities.
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The
substitutersoption innix.settingsuses the orderof the substituters listed to define priority. Prior to #139075,
the corresponding option
binaryCachesis declared in thenixnamespace,which is guaranteed to be merged last. However, the order of merging isn't
guaranteed in submodules. This cause definitions to be appended to the default
value instead of prepended, breaking backwards compatibility as reported in #158356.
The way this is addressed in the module system is with order priorities via
mkOrderand sorting definitions before merging. This PR restores the previousbehavior by setting a higher priority to the substituters option defined internally,
thus all definitions with default priority will be merged before it. This was chosen because
the
mkRenamedOptionfunction does not preserve order priority so users using legacy options do not haveprecise control on placement.
This change should suffice for simple configuration, but further revision to the module system
is needed for to make various
mk*functions aware of order priorities.Motivation for this change
Things done
sandbox = trueset innix.conf? (See Nix manual)nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage./result/bin/)nixos/doc/manual/md-to-db.shto update generated release notes