flake-compat/default.nix
2024-05-02 20:09:04 -07:00

241 lines
8.7 KiB
Nix

# Compatibility function to allow flakes to be used by
# non-flake-enabled Nix versions. Given a source tree containing a
# 'flake.nix' and 'flake.lock' file, it fetches the flake inputs and
# calls the flake's 'outputs' function. It then returns an attrset
# containing 'defaultNix' (to be used in 'default.nix'), 'shellNix'
# (to be used in 'shell.nix').
{ src, system ? builtins.currentSystem or "unknown-system" }:
let
lockFilePath = src + "/flake.lock";
lockFile = builtins.fromJSON (builtins.readFile lockFilePath);
fetchTree =
info:
if info.type == "github" then
{ outPath =
fetchTarball
({ url = "https://api.${info.host or "github.com"}/repos/${info.owner}/${info.repo}/tarball/${info.rev}"; }
// (if info ? narHash then { sha256 = info.narHash; } else {})
);
rev = info.rev;
shortRev = builtins.substring 0 7 info.rev;
lastModified = info.lastModified;
lastModifiedDate = formatSecondsSinceEpoch info.lastModified;
narHash = info.narHash;
}
else if info.type == "git" then
{ outPath =
builtins.fetchGit
({ url = info.url; }
// (if info ? rev then { inherit (info) rev; } else {})
// (if info ? ref then { inherit (info) ref; } else {})
// (if info ? submodules then { inherit (info) submodules; } else {})
);
lastModified = info.lastModified;
lastModifiedDate = formatSecondsSinceEpoch info.lastModified;
narHash = info.narHash;
} // (if info ? rev then {
rev = info.rev;
shortRev = builtins.substring 0 7 info.rev;
} else {
})
else if info.type == "path" then
{ outPath = builtins.path { path = info.path; };
narHash = info.narHash;
}
else if info.type == "tarball" then
{ outPath =
fetchTarball
({ inherit (info) url; }
// (if info ? narHash then { sha256 = info.narHash; } else {})
);
}
else if info.type == "gitlab" then
{ inherit (info) rev narHash lastModified;
outPath =
fetchTarball
({ url = "https://${info.host or "gitlab.com"}/api/v4/projects/${info.owner}%2F${info.repo}/repository/archive.tar.gz?sha=${info.rev}"; }
// (if info ? narHash then { sha256 = info.narHash; } else {})
);
shortRev = builtins.substring 0 7 info.rev;
}
else if info.type == "sourcehut" then
{ inherit (info) rev narHash lastModified;
outPath =
fetchTarball
({ url = "https://${info.host or "git.sr.ht"}/${info.owner}/${info.repo}/archive/${info.rev}.tar.gz"; }
// (if info ? narHash then { sha256 = info.narHash; } else {})
);
shortRev = builtins.substring 0 7 info.rev;
}
else
# FIXME: add Mercurial inputs.
throw "flake input has unsupported input type '${info.type}'";
callFlake4 = flakeSrc: locks:
let
flake = import (flakeSrc + "/flake.nix");
inputs = builtins.mapAttrs (n: v:
if v.flake or true
then callFlake4 (fetchTree (v.locked // v.info)) v.inputs
else fetchTree (v.locked // v.info)) locks;
outputs = flakeSrc // (flake.outputs (inputs // {self = outputs;}));
in
assert flake.edition == 201909;
outputs;
callLocklessFlake = flakeSrc:
let
flake = import (flakeSrc + "/flake.nix");
outputs = flakeSrc // (flake.outputs ({ self = outputs; }));
in outputs;
rootSrc = let
# Try to clean the source tree by using fetchGit, if this source
# tree is a valid git repository.
tryFetchGit = src:
if isGit && !isShallow
then
let res = builtins.fetchGit src;
in if res.rev == "0000000000000000000000000000000000000000" then removeAttrs res ["rev" "shortRev"] else res
else {
outPath =
# Massage `src` into a store path.
if builtins.isPath src
then
if dirOf (toString src) == builtins.storeDir
# `builtins.storePath` is not available in pure-eval mode.
&& builtins ? currentSystem
then
# If it's already a store path, don't copy it again.
builtins.storePath src
else
"${src}"
else
src;
};
# NB git worktrees have a file for .git, so we don't check the type of .git
isGit = builtins.pathExists (src + "/.git");
isShallow = builtins.pathExists (src + "/.git/shallow");
in
{ lastModified = 0; lastModifiedDate = formatSecondsSinceEpoch 0; }
// (if src ? outPath then src else tryFetchGit src);
# Format number of seconds in the Unix epoch as %Y%m%d%H%M%S.
formatSecondsSinceEpoch = t:
let
rem = x: y: x - x / y * y;
days = t / 86400;
secondsInDay = rem t 86400;
hours = secondsInDay / 3600;
minutes = (rem secondsInDay 3600) / 60;
seconds = rem t 60;
# Courtesy of https://stackoverflow.com/a/32158604.
z = days + 719468;
era = (if z >= 0 then z else z - 146096) / 146097;
doe = z - era * 146097;
yoe = (doe - doe / 1460 + doe / 36524 - doe / 146096) / 365;
y = yoe + era * 400;
doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
mp = (5 * doy + 2) / 153;
d = doy - (153 * mp + 2) / 5 + 1;
m = mp + (if mp < 10 then 3 else -9);
y' = y + (if m <= 2 then 1 else 0);
pad = s: if builtins.stringLength s < 2 then "0" + s else s;
in "${toString y'}${pad (toString m)}${pad (toString d)}${pad (toString hours)}${pad (toString minutes)}${pad (toString seconds)}";
allNodes =
builtins.mapAttrs
(key: node:
let
sourceInfo =
if key == lockFile.root
then rootSrc
else fetchTree (node.info or {} // removeAttrs node.locked ["dir"]);
subdir = if key == lockFile.root then "" else node.locked.dir or "";
outPath = sourceInfo + ((if subdir == "" then "" else "/") + subdir);
flake = import (outPath + "/flake.nix");
inputs = builtins.mapAttrs
(inputName: inputSpec: allNodes.${resolveInput inputSpec})
(node.inputs or {});
# Resolve a input spec into a node name. An input spec is
# either a node name, or a 'follows' path from the root
# node.
resolveInput = inputSpec:
if builtins.isList inputSpec
then getInputByPath lockFile.root inputSpec
else inputSpec;
# Follow an input path (e.g. ["dwarffs" "nixpkgs"]) from the
# root node, returning the final node.
getInputByPath = nodeName: path:
if path == []
then nodeName
else
getInputByPath
# Since this could be a 'follows' input, call resolveInput.
(resolveInput lockFile.nodes.${nodeName}.inputs.${builtins.head path})
(builtins.tail path);
outputs = flake.outputs (inputs // { self = result; });
result =
outputs
# We add the sourceInfo attribute for its metadata, as they are
# relevant metadata for the flake. However, the outPath of the
# sourceInfo does not necessarily match the outPath of the flake,
# as the flake may be in a subdirectory of a source.
# This is shadowed in the next //
// sourceInfo
// {
# This shadows the sourceInfo.outPath
inherit outPath;
inherit inputs; inherit outputs; inherit sourceInfo; _type = "flake";
};
in
if node.flake or true then
assert builtins.isFunction flake.outputs;
result
else
sourceInfo
)
lockFile.nodes;
result =
if !(builtins.pathExists lockFilePath)
then callLocklessFlake rootSrc
else if lockFile.version == 4
then callFlake4 rootSrc (lockFile.inputs)
else if lockFile.version >= 5 && lockFile.version <= 7
then allNodes.${lockFile.root}
else throw "lock file '${lockFilePath}' has unsupported version ${toString lockFile.version}";
in
rec {
defaultNix =
(builtins.removeAttrs result ["__functor"])
// (if result ? defaultPackage.${system} then { default = result.defaultPackage.${system}; } else {})
// (if result ? packages.${system}.default then { default = result.packages.${system}.default; } else {});
shellNix =
defaultNix
// (if result ? devShell.${system} then { default = result.devShell.${system}; } else {})
// (if result ? devShells.${system}.default then { default = result.devShells.${system}.default; } else {});
}