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Nix flake template 可以有 welcomeText 这一个字段，在 nix flake init 写入文件后就会展示这些文字，并且自带 Markdown 渲染。
纯 Nix 实现的 nix-eval-jobs —— eval-jobs.nix 来了（
{ lib }:
let
# If cond is true, then return the value, return null otherwise.
optionalNullable = # ... -> Nullable x
cond: # Bool
x: # x
if cond then x else null;
# Map elements to other elements or nulls and filter out nulls.
mapNullables = # ... -> [x] -> [x]
f: # x -> Nullable x
lib.lists.concatMap (
x:
let
y = f x;
in
if y != null then [ y ] else [ ]
);
# Transform the attrset and optionally filter out some elements.
filterMapAttrsRecursiveCond = # ... -> Attrset
recursePred: # AttrSet -> Bool | Whether to recurse into this attrset or treat it as leaf.
mapper: # [String] -> Any -> Nullable Any | Map this leaf element given its path.
attrs: # AttrSet | The attrset to transform.
let
recurseImpl = # ... -> Attrset
path: # [String]
attrs: # Attrset
lib.pipe attrs [
lib.attrsets.attrsToList
(mapNullables (
{ name, value }:
let
subPath = path ++ [ name ];
shouldRecurse = lib.isAttrs value && recursePred value;
newValue = if shouldRecurse then recurseImpl subPath value else mapper subPath value;
in
lib.mapNullable (lib.attrsets.nameValuePair name) newValue
))
lib.attrsets.listToAttrs
];
in
recurseImpl [ ] attrs;
# Selectively retrieve packages with some convenient metadata and filter out non-derivation
# elements using a custom predicate.
evalJobsWithPred = # ... -> [AttrSet]
drvPred: # Derivation -> Bool | Whether to build this derivation.
packageSet: # AttrSet | Package set to process.
let
toJobMetadata = path: drv: {
inherit drv;
inherit (drv)
name
drvPath
outputs
system
;
attr = lib.strings.concatStringsSep "." path;
attrPath = path;
outPaths = lib.lists.map (outputName: drv.${outputName}.outPath) drv.outputs;
type = "jobMetadata";
};
filteredPkgs = filterMapAttrsRecursiveCond (attrs: !(lib.isDerivation attrs)) (
path: value: optionalNullable (lib.isDerivation value && drvPred value) (toJobMetadata path value)
) packageSet;
flattenedPkgsList =
let
flattenImpl =
value:
if lib.isAttrs value then
if value.type or "" == "jobMetadata" then
[ value ]
else
lib.lists.concatMap flattenImpl (lib.attrsets.attrValues value)
else
[ ];
in
flattenImpl filteredPkgs;
in
flattenedPkgsList;
# Default predicate for filter derivations that needn't to built.
defaultDrvPred = # ... -> Bool
drv: # Derivation
let
isBuildable =
drv:
let
licenseFromMeta = drv.meta.license or [ ];
licenseList = if lib.isList licenseFromMeta then licenseFromMeta else [ licenseFromMeta ];
in
!(drv.meta.broken or false) && lib.lists.all (license: license.free or true) licenseList;
isCacheable = drv: !(drv.preferLocalBuild or false);
in
isBuildable drv && isCacheable drv;
# Selectively retrieve packages with some convenient metadata and filter out non-derivation
# elements.
evalJobs = # ... -> [AttrSet]
packageSet: # AttrSet | Package set to process.
evalJobsWithPred defaultDrvPred packageSet;
in
{
inherit
evalJobs
evalJobsWithPred
defaultDrvPred
;
}
最近更新了 NVIDIA，结果 Niri 变得非常卡顿。原因是 NVIDIA 的 DRM 设备路径从 /dev/dri/renderD129 改变为了 /dev/dri/renderD128，Niri 因此使用了 Intel 显卡的 DRM 设备。因此建议在引用设备文件路径时，尽可能使用稳定的表示，比如这里 /dev/dri/by-path/pci-0000:01:00.0-render 就相对更加稳定；又比如在指定硬盘设备文件路径时使用 /dev/disk/by-id，这是按照硬盘型号来选择的。
Nix 打包时可能会遇到需要引用包自身的情况，如果 finalAttrs 可用，则可以用 finalAttrs.finalPackage。但是如果没办法使用 finalAttrs，情况就不一样了。finalPackage 可以通过 package.nix 这个 lambda 的参数传入，在 callPackage 后利用 let in 或 fix 函数来把这个结果传入进去。这样的问题在于传入的 finalPackage 不会跟随 override 和 overrideAttrs 变化。
我的解决方案是在 callPackage 后替换原有的 override 和 overrideAttrs 为自己的版本，调用原来的 override/overrideAttrs 后额外 override 一次 finalPackage 参数。
假设有以下 package.nix：
{
stdenvNoCC,
testFinalPackage,
myText ? "myText",
}:
stdenvNoCC.mkDerivation {
pname = "test-package";
version = "0";
dontUnpack = true;
installPhase = ''
echo ${myText} > $out
'';
passthru.finalPackage = testFinalPackage;
}
以下代码片段实现了 override 和 overrideAttrs 自动传入新 finalPackage：
let
pkgs = import <nixpkgs> { };
lib = pkgs.lib;
in
let
makePackageOverridable =
finalPackageName: package:
package
// {
override =
args:
let
overriddenPackage = ((package.override args).override { ${finalPackageName} = newPackage; });
newPackage = makePackageOverridable finalPackageName overriddenPackage;
in
newPackage;
overrideAttrs =
args:
let
overriddenPackage = ((package.overrideAttrs args).override { ${finalPackageName} = newPackage; });
newPackage = makePackageOverridable finalPackageName overriddenPackage;
in
newPackage;
};
finalPackageAwareCallPackage =
callPackage: func: finalPackageName: attrs:
let
called = callPackage func (attrs // { ${finalPackageName} = finalPackage; });
finalPackage = makePackageOverridable finalPackageName called;
in
finalPackage;
p = finalPackageAwareCallPackage pkgs.callPackage ./package.nix "testFinalPackage" { };
in
{
inherit pkgs lib;
inherit p;
}
在 Nix REPL 中测试：
nix-repl> :l ./test.nix
Added 3 variables.
nix-repl> p
«derivation /nix/store/a5a5pykbm30fgyhy40nqz0iis969k6yc-test-package-0.drv»
nix-repl> p.finalPackage
«derivation /nix/store/a5a5pykbm30fgyhy40nqz0iis969k6yc-test-package-0.drv»
nix-repl> p2 = (p.override { myText = "myText2"; }).overrideAttrs { version = "1"; }
Updated p2.
nix-repl> p2
«derivation /nix/store/wpxlrqdqminbhhsn3g1yws2160lnwn5k-test-package-1.drv»
nix-repl> p2.finalPackage
«derivation /nix/store/wpxlrqdqminbhhsn3g1yws2160lnwn5k-test-package-1.drv»