84 lines
2.8 KiB
Nix
84 lines
2.8 KiB
Nix
# Compatability function to allow flakes to be used by
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# non-flake-enabled Nix versions. Given a source tree containing a
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# 'flake.nix' and 'flake.lock' file, it fetches the flake inputs and
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# calls the flake's 'outputs' function. It then returns an attrset
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# containing 'defaultNix' (to be used in 'default.nix'), 'shellNix'
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# (to be used in 'shell.nix').
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{ src, system ? builtins.currentSystem or "unknown-system" }:
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let
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lockFile = builtins.fromJSON (builtins.readFile (src + "/flake.lock"));
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fetchTree =
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{ info, locked, ... }:
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if locked.type == "github" then
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{ outPath = fetchTarball "https://api.github.com/repos/${locked.owner}/${locked.repo}/tarball/${locked.rev}";
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rev = locked.rev;
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shortRev = builtins.substring 0 7 locked.rev;
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lastModified = formatSecondsSinceEpoch info.lastModified;
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narHash = info.narHash;
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}
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else
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# FIXME: add Git, Mercurial, tarball inputs.
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throw "flake input has unsupported input type '${locked.type}'";
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callFlake = flakeSrc: locks:
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let
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flake = import (flakeSrc + "/flake.nix");
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inputs = builtins.mapAttrs (n: v:
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if v.flake or true
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then callFlake (fetchTree v) v.inputs
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else fetchTree v) locks;
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outputs = flakeSrc // (flake.outputs (inputs // {self = outputs;}));
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in
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assert flake.edition == 201909;
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outputs;
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src' =
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(if src ? outPath then src else { outPath = src; })
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// { lastModified = formatSecondsSinceEpoch 0; };
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# Format number of seconds in the Unix epoch as %Y%m%d%H%M%S.
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formatSecondsSinceEpoch = t:
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let
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rem = x: y: x - x / y * y;
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days = t / 86400;
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secondsInDay = rem t 86400;
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hours = secondsInDay / 3600;
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minutes = (rem secondsInDay 3600) / 60;
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seconds = rem t 60;
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# Courtesy of https://stackoverflow.com/a/32158604.
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z = days + 719468;
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era = (if z >= 0 then z else z - 146096) / 146097;
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doe = z - era * 146097;
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yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
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y = yoe + era * 400;
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doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
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mp = (5 * doy + 2) / 153;
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d = doy - (153 * mp + 2) / 5 + 1;
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m = mp + (if mp < 10 then 3 else -9);
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y' = y + (if m <= 2 then 1 else 0);
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pad = s: if builtins.stringLength s < 2 then "0" + s else s;
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in "${toString y'}${pad (toString m)}${pad (toString d)}${pad (toString hours)}${pad (toString minutes)}${pad (toString seconds)}";
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result = callFlake src' (lockFile.inputs);
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in
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assert lockFile.version == 4;
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rec {
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defaultNix =
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result
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// (if result ? defaultPackage.${system} then { default = result.defaultPackage.${system}; } else {});
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shellNix =
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defaultNix
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// (if result ? devShell.${system} then { default = result.devShell.${system}; } else {});
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}
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