core/pkgs/build-support/checkpoint-build.nix
2024-05-13 22:24:10 +01:00

90 lines
3.4 KiB
Nix

{ 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;
}