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ab4281e967
The concept of having a "minimum supported Nix version" doesn't work anymore today, for the following reasons: - With multiple forks / implementations of Nix available, their feature sets and versions will differ. We'd need *multiple* minimum versions, one for each implementation. - Lix does not expose its real version. It only reports "2.18.3-lix", even though its real version is in the 2.90+ range. - A minimum version has the expectation that it could be *raised* in the future. That's not possible with Lix, because Lix will always and forever report the above version. - A minimum version has the expectation that *all* versions bigger than the minimum are supported. That was already quite a stretch when minver was 2.3 and none of the Nix versions between 2.4 and 2.23 were packed anymore. But it's impossible for us to test all these non-LTS versions anyway: We don't have Nix 2.18, 2.19, 2.20, 2.21, 2.22, 2.23, 2.25, 2.26 and 2.27 available in Nixpkgs at the time of this writing. With their policy around `builtins.nixVersion`, Lix forces our hand: We need to replace minver.nix with a "feature detection" mechanism. This PR introduces the first two features: - The availability of `builtins.nixVersion`: If this is not available, the version of Nix is so old, that we surely don't support it anymore. - The value of `builtins.nixVersion` being greater or equal to 2.18. Note, that this does **not** imply support for Nix 2.18. Instead, explicitly supported versions of Lix and Nix are only these that we actually test against. If, eventually, we realize that the supported versions have advanced and Nixpkgs has adopted a feature only available in newer versions, we will have to add a feature check for this. Put differently: The list of features in `minfeatures.nix` is not expected to be complete. It's a list of known-to-be-bad conditions that will cause problems when evaluating Nixpkgs. Their only purpose is to be able to show a helpful error message. Some other versions might also not be supported, but might fail with more subtle errors. That's just reality and has always been the case previously as well.
34 lines
1.1 KiB
Nix
34 lines
1.1 KiB
Nix
let
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missingFeatures = map ({ description, ... }: description) (import ./lib/minfeatures.nix).missing;
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in
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if missingFeatures != [ ] then
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abort ''
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This version of Nixpkgs requires an implementation of Nix with the following features:
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- ${builtins.concatStringsSep "\n- " missingFeatures}
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Your are evaluating with Nix ${builtins.nixVersion or "(too old to know)"}, please upgrade:
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- If you are running NixOS, `nixos-rebuild' can be used to upgrade your system.
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- Alternatively, with Nix > 2.0 `nix upgrade-nix' can be used to imperatively
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upgrade Nix. You may use `nix-env --version' to check which version you have.
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- If you installed Nix using the install script (https://nixos.org/nix/install),
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it is safe to upgrade by running it again:
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curl -L https://nixos.org/nix/install | sh
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For more information, please see the NixOS release notes at
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https://nixos.org/nixos/manual or locally at
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${toString ./nixos/doc/manual/release-notes}.
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If you need further help, see https://nixos.org/nixos/support.html
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''
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else
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import ./pkgs/top-level/impure.nix
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