A setting to follow XDG Base Directory standard

XDG Base Directory is a standard for locations for storing various files. Nix has a few files which seem to fit in the standard, but currently use a custom location directly in the user's ~, polluting it: - ~/.nix-profile - ~/.nix-defexpr - ~/.nix-channels This commit adds a config option (use-xdg-base-directories) to follow the XDG spec and instead use the following locations: - $XDG_STATE_HOME/nix/profile - $XDG_STATE_HOME/nix/defexpr - $XDG_STATE_HOME/nix/channels If $XDG_STATE_HOME is not set, it is assumed to be ~/.local/state. Co-authored-by: Théophane Hufschmitt <7226587+thufschmitt@users.noreply.github.com> Co-authored-by: Tim Fenney <kodekata@gmail.com> Co-authored-by: pasqui23 <pasqui23@users.noreply.github.com> Co-authored-by: Artturin <Artturin@artturin.com> Co-authored-by: John Ericson <Ericson2314@Yahoo.com>
2024-11-25 08:12:29 +00:00 · 2021-11-17 23:35:21 +03:00 · 2021-11-17 23:35:21 +03:00 · 2384d36083
commit 2384d36083
parent a31d7d4e5e
16 changed files with 153 additions and 20 deletions
--- a/doc/manual/src/command-ref/env-common.md
+++ b/doc/manual/src/command-ref/env-common.md
@ -91,3 +91,16 @@ Most Nix commands interpret the following environment variables:
    variable sets the initial size of the heap in bytes. It defaults to
    384 MiB. Setting it to a low value reduces memory consumption, but
    will increase runtime due to the overhead of garbage collection.
+
+## XDG Base Directory
+
+New Nix commands conform to the [XDG Base Directory Specification], and use the following environment variables to determine locations of various state and configuration files:
+
+- [`XDG_CONFIG_HOME`]{#env-XDG_CONFIG_HOME} (default `~/.config`)
+- [`XDG_STATE_HOME`]{#env-XDG_STATE_HOME} (default `~/.local/state`)
+- [`XDG_CACHE_HOME`]{#env-XDG_CACHE_HOME} (default `~/.cache`)
+
+Classic Nix commands can also be made to follow this standard using the [`use-xdg-base-directories`] configuration option.
+
+[XDG Base Directory Specification]: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
+[`use-xdg-base-directories`]: ../command-ref/conf-file.md#conf-use-xdg-base-directories
--- a/scripts/install-multi-user.sh
+++ b/scripts/install-multi-user.sh
@ -136,7 +136,7 @@ EOF
    cat <<EOF
 $step. Delete the files Nix added to your system:

-  sudo rm -rf /etc/nix $NIX_ROOT $ROOT_HOME/.nix-profile $ROOT_HOME/.nix-defexpr $ROOT_HOME/.nix-channels $HOME/.nix-profile $HOME/.nix-defexpr $HOME/.nix-channels
+  sudo rm -rf "/etc/nix" "$NIX_ROOT" "$ROOT_HOME/.nix-profile" "$ROOT_HOME/.nix-defexpr" "$ROOT_HOME/.nix-channels" "$ROOT_HOME/.local/state/nix" "$ROOT_HOME/.cache/nix" "$HOME/.nix-profile" "$HOME/.nix-defexpr" "$HOME/.nix-channels" "$HOME/.local/state/nix" "$HOME/.cache/nix"

 and that is it.

--- a/scripts/install-nix-from-closure.sh
+++ b/scripts/install-nix-from-closure.sh
@ -188,6 +188,8 @@ fi
 # shellcheck source=./nix-profile.sh.in
 . "$nix/etc/profile.d/nix.sh"

+NIX_LINK="$HOME/.nix-profile"
+
 if ! "$nix/bin/nix-env" -i "$nix"; then
    echo "$0: unable to install Nix into your default profile" >&2
    exit 1
@ -196,7 +198,7 @@ fi
 # Install an SSL certificate bundle.
 if [ -z "$NIX_SSL_CERT_FILE" ] || ! [ -f "$NIX_SSL_CERT_FILE" ]; then
    "$nix/bin/nix-env" -i "$cacert"
-    export NIX_SSL_CERT_FILE="$HOME/.nix-profile/etc/ssl/certs/ca-bundle.crt"
+    export NIX_SSL_CERT_FILE="$NIX_LINK/etc/ssl/certs/ca-bundle.crt"
 fi

 # Subscribe the user to the Nixpkgs channel and fetch it.
@ -214,8 +216,8 @@ fi

 added=
 p=
-p_sh=$HOME/.nix-profile/etc/profile.d/nix.sh
-p_fish=$HOME/.nix-profile/etc/profile.d/nix.fish
+p_sh=$NIX_LINK/etc/profile.d/nix.sh
+p_fish=$NIX_LINK/etc/profile.d/nix.fish
 if [ -z "$NIX_INSTALLER_NO_MODIFY_PROFILE" ]; then
    # Make the shell source nix.sh during login.
    for i in .bash_profile .bash_login .profile; do
--- a/scripts/nix-profile-daemon.sh.in
+++ b/scripts/nix-profile-daemon.sh.in
@ -2,7 +2,33 @@
 if [ -n "${__ETC_PROFILE_NIX_SOURCED:-}" ]; then return; fi
 __ETC_PROFILE_NIX_SOURCED=1

-export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"
+NIX_LINK=$HOME/.nix-profile
+if [ -n "$XDG_STATE_HOME" ]; then
+    NIX_LINK_NEW="$XDG_STATE_HOME/nix/profile"
+else
+    NIX_LINK_NEW=$HOME/.local/state/nix/profile
+fi
+if ! [ -e "$NIX_LINK" ]; then
+    NIX_LINK="$NIX_LINK_NEW"
+else
+    if [ -t 2 ] && [ -e "$NIX_LINK_NEW" ]; then
+        warning="\033[1;35mwarning:\033[0m"
+        printf "$warning Both %s and legacy %s exist; using the latter.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
+        if [ "$(realpath "$NIX_LINK")" = "$(realpath "$NIX_LINK_NEW")" ]; then
+            printf "         Since the profiles match, you can safely delete either of them.\n" 1>&2
+        else
+            # This should be an exceptionally rare occasion: the only way to get it would be to
+            # 1. Update to newer Nix;
+            # 2. Remove .nix-profile;
+            # 3. Set the $NIX_LINK_NEW to something other than the default user profile;
+            # 4. Roll back to older Nix.
+            # If someone did all that, they can probably figure out how to migrate the profile.
+            printf "$warning Profiles do not match. You should manually migrate from %s to %s.\n" "$NIX_LINK" "$NIX_LINK_NEW" 1>&2
+        fi
+    fi
+fi
+
+export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"

 # Set $NIX_SSL_CERT_FILE so that Nixpkgs applications like curl work.
 if [ -n "${NIX_SSL_CERT_FILE:-}" ]; then
@ -34,4 +60,5 @@ else
  unset -f check_nix_profiles
 fi

-export PATH="$HOME/.nix-profile/bin:@localstatedir@/nix/profiles/default/bin:$PATH"
+export PATH="$NIX_LINK/bin:@localstatedir@/nix/profiles/default/bin:$PATH"
+unset NIX_LINK
--- a/scripts/nix-profile.sh.in
+++ b/scripts/nix-profile.sh.in
@ -2,11 +2,35 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then

    # Set up the per-user profile.

-    NIX_LINK=$HOME/.nix-profile
+    NIX_LINK="$HOME/.nix-profile"
+    if [ -n "$XDG_STATE_HOME" ]; then
+        NIX_LINK_NEW="$XDG_STATE_HOME/nix/profile"
+    else
+        NIX_LINK_NEW="$HOME/.local/state/nix/profile"
+    fi
+    if ! [ -e "$NIX_LINK" ]; then
+        NIX_LINK="$NIX_LINK_NEW"
+    else
+        if [ -t 2 ] && [ -e "$NIX_LINK_NEW" ]; then
+            warning="\033[1;35mwarning:\033[0m"
+            printf "$warning Both %s and legacy %s exist; using the latter.\n" "$NIX_LINK_NEW" "$NIX_LINK" 1>&2
+            if [ "$(realpath "$NIX_LINK")" = "$(realpath "$NIX_LINK_NEW")" ]; then
+                printf "         Since the profiles match, you can safely delete either of them.\n" 1>&2
+            else
+                # This should be an exceptionally rare occasion: the only way to get it would be to
+                # 1. Update to newer Nix;
+                # 2. Remove .nix-profile;
+                # 3. Set the $NIX_LINK_NEW to something other than the default user profile;
+                # 4. Roll back to older Nix.
+                # If someone did all that, they can probably figure out how to migrate the profile.
+                printf "$warning Profiles do not match. You should manually migrate from %s to %s.\n" "$NIX_LINK" "$NIX_LINK_NEW" 1>&2
+            fi
+        fi
+    fi

    # Set up environment.
    # This part should be kept in sync with nixpkgs:nixos/modules/programs/environment.nix
-    export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"
+    export NIX_PROFILES="@localstatedir@/nix/profiles/default $NIX_LINK"

    # Set $NIX_SSL_CERT_FILE so that Nixpkgs applications like curl work.
    if [ -e /etc/ssl/certs/ca-certificates.crt ]; then # NixOS, Ubuntu, Debian, Gentoo, Arch
@ -31,5 +55,5 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
    fi

    export PATH="$NIX_LINK/bin:$PATH"
-    unset NIX_LINK
+    unset NIX_LINK NIX_LINK_NEW
 fi
--- a/src/libexpr/eval.cc
+++ b/src/libexpr/eval.cc
@ -2496,7 +2496,7 @@ Strings EvalSettings::getDefaultNixPath()
                res.push_back(s ? *s + "=" + p : p);
        };

-        add(getHome() + "/.nix-defexpr/channels");
+        add(settings.useXDGBaseDirectories ? getStateDir() + "/nix/defexpr/channels" : getHome() + "/.nix-defexpr/channels");
        add(settings.nixStateDir + "/profiles/per-user/root/channels/nixpkgs", "nixpkgs");
        add(settings.nixStateDir + "/profiles/per-user/root/channels");

--- a/src/libstore/globals.hh
+++ b/src/libstore/globals.hh
@ -975,6 +975,27 @@ public:
          resolves to a different location from that of the build machine. You
          can enable this setting if you are sure you're not going to do that.
        )"};
+
+    Setting<bool> useXDGBaseDirectories{
+        this, false, "use-xdg-base-directories",
+        R"(
+          If set to `true`, Nix will conform to the [XDG Base Directory Specification] for files in `$HOME`.
+          The environment variables used to implement this are documented in the [Environment Variables section](@docroot@/installation/env-variables.md).
+
+          [XDG Base Directory Specification]: https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html
+
+          > **Warning**
+          > This changes the location of some well-known symlinks that Nix creates, which might break tools that rely on the old, non-XDG-conformant locations.
+
+          In particular, the following locations change:
+
+          | Old               | New                            |
+          |-------------------|--------------------------------|
+          | `~/.nix-profile`  | `$XDG_STATE_HOME/nix/profile`  |
+          | `~/.nix-defexpr`  | `$XDG_STATE_HOME/nix/defexpr`  |
+          | `~/.nix-channels` | `$XDG_STATE_HOME/nix/channels` |
+        )"
+    };
 };


--- a/src/libstore/profiles.cc
+++ b/src/libstore/profiles.cc
@ -282,7 +282,7 @@ std::string optimisticLockProfile(const Path & profile)

 Path profilesDir()
 {
-    auto profileRoot = getDataDir() + "/nix/profiles";
+    auto profileRoot = createNixStateDir() + "/profiles";
    createDirs(profileRoot);
    return profileRoot;
 }
@ -290,7 +290,7 @@ Path profilesDir()

 Path getDefaultProfile()
 {
-    Path profileLink = getHome() + "/.nix-profile";
+    Path profileLink = settings.useXDGBaseDirectories ? createNixStateDir() + "/profile" : getHome() + "/.nix-profile";
    try {
        auto profile =
            getuid() == 0
--- a/src/libstore/profiles.hh
+++ b/src/libstore/profiles.hh
@ -72,8 +72,9 @@ std::string optimisticLockProfile(const Path & profile);
   profiles. */
 Path profilesDir();

-/* Resolve ~/.nix-profile. If ~/.nix-profile doesn't exist yet, create
-   it. */
+/* Resolve the default profile (~/.nix-profile by default, $XDG_STATE_HOME/
+   nix/profile if XDG Base Directory Support is enabled), and create if doesn't
+   exist */
 Path getDefaultProfile();

 }
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@ -608,6 +608,19 @@ Path getDataDir()
    return dataDir ? *dataDir : getHome() + "/.local/share";
 }

+Path getStateDir()
+{
+    auto stateDir = getEnv("XDG_STATE_HOME");
+    return stateDir ? *stateDir : getHome() + "/.local/state";
+}
+
+Path createNixStateDir()
+{
+    Path dir = getStateDir() + "/nix";
+    createDirs(dir);
+    return dir;
+}
+

 std::optional<Path> getSelfExe()
 {
--- a/src/libutil/util.hh
+++ b/src/libutil/util.hh
@ -158,6 +158,12 @@ Path getDataDir();
 /* Return the path of the current executable. */
 std::optional<Path> getSelfExe();

+/* Return $XDG_STATE_HOME or $HOME/.local/state. */
+Path getStateDir();
+
+/* Create the Nix state directory and return the path to it. */
+Path createNixStateDir();
+
 /* Create a directory and all its parents, if necessary.  Returns the
   list of created directories, in order of creation. */
 Paths createDirs(const Path & path);
--- a/src/nix-channel/nix-channel.cc
+++ b/src/nix-channel/nix-channel.cc
@ -164,8 +164,8 @@ static int main_nix_channel(int argc, char ** argv)
    {
        // Figure out the name of the `.nix-channels' file to use
        auto home = getHome();
-        channelsList = home + "/.nix-channels";
-        nixDefExpr = home + "/.nix-defexpr";
+        channelsList = settings.useXDGBaseDirectories ? createNixStateDir() + "/channels" : home + "/.nix-channels";
+        nixDefExpr = settings.useXDGBaseDirectories ? createNixStateDir() + "/defexpr" : home + "/.nix-defexpr";

        // Figure out the name of the channels profile.
        profile = profilesDir() + "/channels";
--- a/src/nix-env/nix-env.cc
+++ b/src/nix-env/nix-env.cc
@ -1289,7 +1289,7 @@ static void opSwitchProfile(Globals & globals, Strings opFlags, Strings opArgs)
        throw UsageError("exactly one argument expected");

    Path profile = absPath(opArgs.front());
-    Path profileLink = getHome() + "/.nix-profile";
+    Path profileLink = settings.useXDGBaseDirectories ? createNixStateDir() + "/profile" : getHome() + "/.nix-profile";

    switchLink(profileLink, profile);
 }
@ -1393,7 +1393,10 @@ static int main_nix_env(int argc, char * * argv)
        Globals globals;

        globals.instSource.type = srcUnknown;
-        globals.instSource.nixExprPath = getHome() + "/.nix-defexpr";
+        {
+            Path nixExprPath = settings.useXDGBaseDirectories ? createNixStateDir() + "/defexpr" : getHome() + "/.nix-defexpr";
+            globals.instSource.nixExprPath = nixExprPath;
+        }
        globals.instSource.systemFilter = "*";

        if (!pathExists(globals.instSource.nixExprPath)) {
--- a/tests/common.sh.in
+++ b/tests/common.sh.in
@ -27,6 +27,8 @@ export NIX_REMOTE=$NIX_REMOTE_
 unset NIX_PATH
 export TEST_HOME=$TEST_ROOT/test-home
 export HOME=$TEST_HOME
+unset XDG_STATE_HOME
+unset XDG_DATA_HOME
 unset XDG_CONFIG_HOME
 unset XDG_CONFIG_DIRS
 unset XDG_CACHE_HOME
@ -62,8 +64,8 @@ readLink() {
 }

 clearProfiles() {
-    profiles="$HOME"/.local/share/nix/profiles
-    rm -rf $profiles
+    profiles="$HOME"/.local/state/nix/profiles
+    rm -rf "$profiles"
 }

 clearStore() {
--- a/tests/nix-channel.sh
+++ b/tests/nix-channel.sh
@ -12,6 +12,19 @@ nix-channel --remove xyzzy
 [ -e $TEST_HOME/.nix-channels ]
 [ "$(cat $TEST_HOME/.nix-channels)" = '' ]

+# Test the XDG Base Directories support
+
+export NIX_CONFIG="use-xdg-base-directories = true"
+
+nix-channel --add http://foo/bar xyzzy
+nix-channel --list | grep -q http://foo/bar
+nix-channel --remove xyzzy
+
+unset NIX_CONFIG
+
+[ -e $TEST_HOME/.local/state/nix/channels ]
+[ "$(cat $TEST_HOME/.local/state/nix/channels)" = '' ]
+
 # Create a channel.
 rm -rf $TEST_ROOT/foo
 mkdir -p $TEST_ROOT/foo
--- a/tests/nix-profile.sh
+++ b/tests/nix-profile.sh
@ -56,6 +56,14 @@ nix profile history
 nix profile history | grep "packages.$system.default: ∅ -> 1.0"
 nix profile diff-closures | grep 'env-manifest.nix: ε → ∅'

+# Test XDG Base Directories support
+
+export NIX_CONFIG="use-xdg-base-directories = true"
+nix profile remove 1
+nix profile install $flake1Dir
+[[ $($TEST_HOME/.local/state/nix/profile/bin/hello) = "Hello World" ]]
+unset NIX_CONFIG
+
 # Test upgrading a package.
 printf NixOS > $flake1Dir/who
 printf 2.0 > $flake1Dir/version