nixpkgs/pkgs/build-support/replace-dependency.nix

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{ runCommand, nix, lib }:
# Replace a single dependency in the requisites tree of drv, propagating
# the change all the way up the tree, without a full rebuild. This can be
# useful, for example, to patch a security hole in libc and still use your
# system safely without rebuilding the world. This should be a short term
# solution, as soon as a rebuild can be done the properly rebuild derivation
# should be used. The old dependency and new dependency MUST have the same-length
# name, and ideally should have close-to-identical directory layout.
#
# Example: safe-firefox = replace-dependency {
# drv = firefox;
# old-dependency = glibc;
# new-dependency = overrideDerivation glibc (attrs: {
# patches = attrs.patches ++ [ ./fix-glibc-hole.patch ];
# });
# };
# This will rebuild glibc with your security patch, then copy over firefox
# (and all of its dependencies) without rebuilding further.
{ drv, old-dependency, new-dependency }:
with lib;
let
references = import (runCommand "references.nix" { exportReferencesGraph = [ "graph" drv ]; } ''
(echo {
while read path
do
echo " \"$path\" = ["
read count
read count
while [ "0" != "$count" ]
do
read ref_path
if [ "$ref_path" != "$path" ]
then
echo " (builtins.storePath $ref_path)"
fi
count=$(($count - 1))
done
echo " ];"
done < graph
echo }) > $out
'').outPath;
discard = builtins.unsafeDiscardStringContext;
old-storepath = builtins.storePath (discard (toString old-dependency));
references-of = drv: getAttr (discard (toString drv)) references;
depends-on-old = drv: elem old-storepath (references-of drv) ||
any depends-on-old (references-of drv);
drv-name = drv:
discard (substring 33 (stringLength (builtins.baseNameOf drv)) (builtins.baseNameOf drv));
replace-strings = drv: rewritten-drvs: runCommand (drv-name drv) { nixStore = "${nix}/bin/nix-store"; } ''
$nixStore --dump ${drv} | sed 's|${baseNameOf drv}|'$(basename $out)'|g' | sed -e ${
concatStringsSep " -e " (mapAttrsToList (name: value:
"'s|${baseNameOf name}|${baseNameOf value}|g'"
) rewritten-drvs)
} | $nixStore --restore $out
'';
rewritten-deps = listToAttrs [ {name = discard (toString old-dependency); value = new-dependency;} ];
fn = drv:
if depends-on-old drv
then listToAttrs [ {
name = discard (toString drv);
value = replace-strings drv (rewritten-deps // (fold (drv: acc:
(fn drv) // acc
) {} (references-of drv)));
} ]
else {};
in assert (stringLength (drv-name (toString old-dependency)) == stringLength (drv-name (toString new-dependency)));
getAttr (discard (toString drv)) (fn drv)