core/pkgs/build-support/checkpoint-build.nix

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2024-05-02 00:46:19 +00:00
{ lib
, buildPackages
}:
let
# rudimentary support for cross-compiling
# see: https://github.com/NixOS/nixpkgs/pull/279487#discussion_r1444449726
inherit (buildPackages)
mktemp
rsync
;
in
rec {
/* Prepare a derivation for local builds.
*
* This function prepares checkpoint builds by storing
* the build output and the sources for cross checking.
* The build output can be used later to allow checkpoint builds
* by passing the derivation output to the `mkCheckpointBuild` function.
*
* To build a project with checkpoints, follow these steps:
* - run `prepareCheckpointBuild` on the desired derivation, e.g.
* checkpointArtifacts = prepareCheckpointBuild virtualbox;
* - change something you want in the sources of the package,
* e.g. using source override:
* changedVBox = pkgs.virtuabox.overrideAttrs (old: {
* src = path/to/vbox/sources;
* };
* - use `mkCheckpointBuild changedVBox checkpointArtifacts`
* - enjoy shorter build times
*/
prepareCheckpointBuild = drv: drv.overrideAttrs (old: {
outputs = [ "out" ];
name = drv.name + "-checkpointArtifacts";
# To determine differences between the state of the build directory
# from an earlier build and a later one we store the state of the build
# directory before build, but after patch phases.
# This way, the same derivation can be used multiple times and only changes are detected.
# Additionally, removed files are handled correctly in later builds.
preBuild = (old.preBuild or "") + ''
mkdir -p $out/sources
cp -r ./* $out/sources/
'';
# After the build, the build directory is copied again
# to get the output files.
# We copy the complete build folder, to take care of
# build tools that build in the source directory, instead of
# having a separate build directory such as the Linux kernel.
installPhase = ''
runHook preCheckpointInstall
mkdir -p $out/outputs
cp -r ./* $out/outputs/
runHook postCheckpointInstall
unset postPhases
'';
dontFixup = true;
doInstallCheck = false;
doDist = false;
});
/* Build a derivation based on the checkpoint output generated by
* the `prepareCheckpointBuild` function.
*
* Usage:
* let
* checkpointArtifacts = prepareCheckpointBuild drv;
* in mkCheckpointBuild drv checkpointArtifacts
*/
mkCheckpointBuild = drv: checkpointArtifacts: drv.overrideAttrs (old: {
# The actual checkpoint build phase.
# We compare the changed sources from a previous build with the current and create a patch.
# Afterwards we clean the build directory and copy the previous output files (including the sources).
# The source difference patch is then applied to get the latest changes again to allow short build times.
preBuild = (old.preBuild or "") + ''
set +e
sourceDifferencePatchFile=$(${mktemp}/bin/mktemp)
diff -ur ${checkpointArtifacts}/sources ./ > "$sourceDifferencePatchFile"
set -e
shopt -s dotglob
rm -r *
${rsync}/bin/rsync \
--checksum --times --atimes --chown=$USER:$USER --chmod=+w \
-r ${checkpointArtifacts}/outputs/ .
patch -p 1 -i "$sourceDifferencePatchFile"
rm "$sourceDifferencePatchFile"
'';
});
mkCheckpointedBuild = lib.warn
"`mkCheckpointedBuild` is deprecated, use `mkCheckpointBuild` instead!"
mkCheckpointBuild;
}