home-manager/modules/files.nix
Robert Helgesson 4aa9eb327d
WIP home-manager: avoid profile management during activation
This commit deprecates profile management from the activation script.
The profile management is instead the responsibility of the driving
software, for example, the `home-manager` tool in the case of
standalone installs.

The legacy behavior is still available for backwards compatibility but
may be removed in the future.

The new behavior resolves (or moves us closer to resolving) a number
of long standing open issues:

- `home-manager switch --rollback`, which performs a rollback to the
  previous Home Manager generation before activating. While it was
  previously possible to accomplish this by activating an old
  generation, it did always create a new profile generation.

  This option has been implemented as part of this commit.

- `home-manager switch --test`, which activates the configuration but
  does not create a new profile generation.

  This option has _not_ been implemented here since it relies on the
  current configuration being activated on login, which we do not
  currently do.

- When using the "Home Manager as a NixOS module" installation method
  we previously created an odd `home-manager` per-user "shadow
  profile" for the user. This is no longer necessary.

  This has been implemented as part of this commit.

Fixes #3450
2024-06-22 15:15:55 +02:00

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{ pkgs, config, lib, ... }:
with lib;
let
cfg = filterAttrs (n: f: f.enable) config.home.file;
homeDirectory = config.home.homeDirectory;
fileType = (import lib/file-type.nix {
inherit homeDirectory lib pkgs;
}).fileType;
sourceStorePath = file:
let
sourcePath = toString file.source;
sourceName = config.lib.strings.storeFileName (baseNameOf sourcePath);
in
if builtins.hasContext sourcePath
then file.source
else builtins.path { path = file.source; name = sourceName; };
in
{
options = {
home.file = mkOption {
description = "Attribute set of files to link into the user home.";
default = {};
type = fileType "home.file" "{env}`HOME`" homeDirectory;
};
home-files = mkOption {
type = types.package;
internal = true;
description = "Package to contain all home files";
};
};
config = {
assertions = [(
let
dups =
attrNames
(filterAttrs (n: v: v > 1)
(foldAttrs (acc: v: acc + v) 0
(mapAttrsToList (n: v: { ${v.target} = 1; }) cfg)));
dupsStr = concatStringsSep ", " dups;
in {
assertion = dups == [];
message = ''
Conflicting managed target files: ${dupsStr}
This may happen, for example, if you have a configuration similar to
home.file = {
conflict1 = { source = ./foo.nix; target = "baz"; };
conflict2 = { source = ./bar.nix; target = "baz"; };
}'';
})
];
lib.file.mkOutOfStoreSymlink = path:
let
pathStr = toString path;
name = hm.strings.storeFileName (baseNameOf pathStr);
in
pkgs.runCommandLocal name {} ''ln -s ${escapeShellArg pathStr} $out'';
# This verifies that the links we are about to create will not
# overwrite an existing file.
home.activation.checkLinkTargets = hm.dag.entryBefore ["writeBoundary"] (
let
# Paths that should be forcibly overwritten by Home Manager.
# Caveat emptor!
forcedPaths =
concatMapStringsSep " " (p: ''"$HOME"/${escapeShellArg p}'')
(mapAttrsToList (n: v: v.target)
(filterAttrs (n: v: v.force) cfg));
storeDir = escapeShellArg builtins.storeDir;
check = pkgs.substituteAll {
src = ./files/check-link-targets.sh;
inherit (config.lib.bash) initHomeManagerLib;
inherit forcedPaths storeDir;
};
in
''
function checkNewGenCollision() {
local newGenFiles
newGenFiles="$(readlink -e "$newGenPath/home-files")"
find "$newGenFiles" \( -type f -or -type l \) \
-exec bash ${check} "$newGenFiles" {} +
}
checkNewGenCollision || exit 1
''
);
# This activation script will
#
# 1. Remove files from the old generation that are not in the new
# generation.
#
# 2. Symlink files from the new generation into $HOME.
#
# This order is needed to ensure that we always know which links
# belong to which generation. Specifically, if we're moving from
# generation A to generation B having sets of home file links FA
# and FB, respectively then cleaning before linking produces state
# transitions similar to
#
# FA → FA ∩ FB → (FA ∩ FB) FB = FB
#
# and a failure during the intermediate state FA ∩ FB will not
# result in lost links because this set of links are in both the
# source and target generation.
home.activation.linkGeneration = hm.dag.entryAfter ["writeBoundary"] (
let
link = pkgs.writeShellScript "link" ''
${config.lib.bash.initHomeManagerLib}
newGenFiles="$1"
shift
for sourcePath in "$@" ; do
relativePath="''${sourcePath#$newGenFiles/}"
targetPath="$HOME/$relativePath"
if [[ -e "$targetPath" && ! -L "$targetPath" && -n "$HOME_MANAGER_BACKUP_EXT" ]] ; then
# The target exists, back it up
backup="$targetPath.$HOME_MANAGER_BACKUP_EXT"
run mv $VERBOSE_ARG "$targetPath" "$backup" || errorEcho "Moving '$targetPath' failed!"
fi
if [[ -e "$targetPath" && ! -L "$targetPath" ]] && cmp -s "$sourcePath" "$targetPath" ; then
# The target exists but is identical don't do anything.
verboseEcho "Skipping '$targetPath' as it is identical to '$sourcePath'"
else
# Place that symlink, --force
# This can still fail if the target is a directory, in which case we bail out.
run mkdir -p $VERBOSE_ARG "$(dirname "$targetPath")"
run ln -Tsf $VERBOSE_ARG "$sourcePath" "$targetPath" || exit 1
fi
done
'';
cleanup = pkgs.writeShellScript "cleanup" ''
${config.lib.bash.initHomeManagerLib}
# A symbolic link whose target path matches this pattern will be
# considered part of a Home Manager generation.
homeFilePattern="$(readlink -e ${escapeShellArg builtins.storeDir})/*-home-manager-files/*"
newGenFiles="$1"
shift 1
for relativePath in "$@" ; do
targetPath="$HOME/$relativePath"
if [[ -e "$newGenFiles/$relativePath" ]] ; then
verboseEcho "Checking $targetPath: exists"
elif [[ ! "$(readlink "$targetPath")" == $homeFilePattern ]] ; then
warnEcho "Path '$targetPath' does not link into a Home Manager generation. Skipping delete."
else
verboseEcho "Checking $targetPath: gone (deleting)"
run rm $VERBOSE_ARG "$targetPath"
# Recursively delete empty parent directories.
targetDir="$(dirname "$relativePath")"
if [[ "$targetDir" != "." ]] ; then
pushd "$HOME" > /dev/null
# Call rmdir with a relative path excluding $HOME.
# Otherwise, it might try to delete $HOME and exit
# with a permission error.
run rmdir $VERBOSE_ARG \
-p --ignore-fail-on-non-empty \
"$targetDir"
popd > /dev/null
fi
fi
done
'';
in
''
function linkNewGen() {
_i "Creating home file links in %s" "$HOME"
local newGenFiles
newGenFiles="$(readlink -e "$newGenPath/home-files")"
find "$newGenFiles" \( -type f -or -type l \) \
-exec bash ${link} "$newGenFiles" {} +
}
function cleanOldGen() {
if [[ ! -v oldGenPath || ! -e "$oldGenPath/home-files" ]] ; then
return
fi
_i "Cleaning up orphan links from %s" "$HOME"
local newGenFiles oldGenFiles
newGenFiles="$(readlink -e "$newGenPath/home-files")"
oldGenFiles="$(readlink -e "$oldGenPath/home-files")"
# Apply the cleanup script on each leaf in the old
# generation. The find command below will print the
# relative path of the entry.
find "$oldGenFiles" '(' -type f -or -type l ')' -printf '%P\0' \
| xargs -0 bash ${cleanup} "$newGenFiles"
}
cleanOldGen
linkNewGen
''
);
home.activation.checkFilesChanged = hm.dag.entryBefore ["linkGeneration"] (
let
homeDirArg = escapeShellArg homeDirectory;
in ''
function _cmp() {
if [[ -d $1 && -d $2 ]]; then
diff -rq "$1" "$2" &> /dev/null
else
cmp --quiet "$1" "$2"
fi
}
declare -A changedFiles
'' + concatMapStrings (v:
let
sourceArg = escapeShellArg (sourceStorePath v);
targetArg = escapeShellArg v.target;
in ''
_cmp ${sourceArg} ${homeDirArg}/${targetArg} \
&& changedFiles[${targetArg}]=0 \
|| changedFiles[${targetArg}]=1
'') (filter (v: v.onChange != "") (attrValues cfg))
+ ''
unset -f _cmp
''
);
home.activation.onFilesChange = hm.dag.entryAfter ["linkGeneration"] (
concatMapStrings (v: ''
if (( ''${changedFiles[${escapeShellArg v.target}]} == 1 )); then
if [[ -v DRY_RUN || -v VERBOSE ]]; then
echo "Running onChange hook for" ${escapeShellArg v.target}
fi
if [[ ! -v DRY_RUN ]]; then
${v.onChange}
fi
fi
'') (filter (v: v.onChange != "") (attrValues cfg))
);
# Symlink directories and files that have the right execute bit.
# Copy files that need their execute bit changed.
home-files = pkgs.runCommandLocal
"home-manager-files"
{
nativeBuildInputs = [ pkgs.xorg.lndir ];
}
(''
mkdir -p $out
# Needed in case /nix is a symbolic link.
realOut="$(realpath -m "$out")"
function insertFile() {
local source="$1"
local relTarget="$2"
local executable="$3"
local recursive="$4"
# If the target already exists then we have a collision. Note, this
# should not happen due to the assertion found in the 'files' module.
# We therefore simply log the conflict and otherwise ignore it, mainly
# to make the `files-target-config` test work as expected.
if [[ -e "$realOut/$relTarget" ]]; then
echo "File conflict for file '$relTarget'" >&2
return
fi
# Figure out the real absolute path to the target.
local target
target="$(realpath -m "$realOut/$relTarget")"
# Target path must be within $HOME.
if [[ ! $target == $realOut* ]] ; then
echo "Error installing file '$relTarget' outside \$HOME" >&2
exit 1
fi
mkdir -p "$(dirname "$target")"
if [[ -d $source ]]; then
if [[ $recursive ]]; then
mkdir -p "$target"
lndir -silent "$source" "$target"
else
ln -s "$source" "$target"
fi
else
[[ -x $source ]] && isExecutable=1 || isExecutable=""
# Link the file into the home file directory if possible,
# i.e., if the executable bit of the source is the same we
# expect for the target. Otherwise, we copy the file and
# set the executable bit to the expected value.
if [[ $executable == inherit || $isExecutable == $executable ]]; then
ln -s "$source" "$target"
else
cp "$source" "$target"
if [[ $executable == inherit ]]; then
# Don't change file mode if it should match the source.
:
elif [[ $executable ]]; then
chmod +x "$target"
else
chmod -x "$target"
fi
fi
fi
}
'' + concatStrings (
mapAttrsToList (n: v: ''
insertFile ${
escapeShellArgs [
(sourceStorePath v)
v.target
(if v.executable == null
then "inherit"
else toString v.executable)
(toString v.recursive)
]}
'') cfg
));
};
}