nix-env: Create ~/.nix-defexpr automatically

(cherry picked from commit c9159f8)

Author: edolstra

scripts/nix-profile-daemon.sh.in

@@ -5,18 +5,6 @@ __ETC_PROFILE_NIX_SOURCED=1
 export NIX_USER_PROFILE_DIR="@localstatedir@/nix/profiles/per-user/$USER"
 export NIX_PROFILES="@localstatedir@/nix/profiles/default $HOME/.nix-profile"
 
-if test -w $HOME; then
-  # Set up a default Nix expression from which to install stuff.
-  if [ ! -e $HOME/.nix-defexpr -o -L $HOME/.nix-defexpr ]; then
-      rm -f $HOME/.nix-defexpr
-      mkdir -p $HOME/.nix-defexpr
-      if [ "$USER" != root ]; then
-          ln -s @localstatedir@/nix/profiles/per-user/root/channels $HOME/.nix-defexpr/channels_root
-      fi
-  fi
-fi
-
-
 # Set $NIX_SSL_CERT_FILE so that Nixpkgs applications like curl work.
 if [ ! -z "${NIX_SSL_CERT_FILE:-}" ]; then
     : # Allow users to override the NIX_SSL_CERT_FILE

scripts/nix-profile.sh.in

@@ -7,17 +7,6 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
 
     NIX_USER_PROFILE_DIR=@localstatedir@/nix/profiles/per-user/$USER
 
-    if [ -w "$HOME" ]; then
-        # Set up a default Nix expression from which to install stuff.
-        __nix_defexpr="$HOME"/.nix-defexpr
-        [ -L "$__nix_defexpr" ] && rm -f "$__nix_defexpr"
-        mkdir -m 0755 -p "$__nix_defexpr"
-        if [ "$USER" != root ] && [ ! -L "$__nix_defexpr"/channels_root ]; then
-            ln -s @localstatedir@/nix/profiles/per-user/root/channels "$__nix_defexpr"/channels_root
-        fi
-        unset __nix_defexpr
-    fi
-
     # Append ~/.nix-defexpr/channels to $NIX_PATH so that <nixpkgs>
     # paths work when the user has fetched the Nixpkgs channel.
     export NIX_PATH=${NIX_PATH:+$NIX_PATH:}$HOME/.nix-defexpr/channels

src/nix-env/nix-env.cc

@@ -193,12 +193,6 @@ static void loadDerivations(EvalState & state, Path nixExprPath,
 }
 
 
-static Path getDefNixExprPath()
-{
-    return getHome() + "/.nix-defexpr";
-}
-
-
 static long getPriority(EvalState & state, DrvInfo & drv)
 {
     return drv.queryMetaInt("priority", 0);
@@ -1330,9 +1324,20 @@ static int _main(int argc, char * * argv)
         Globals globals;
 
         globals.instSource.type = srcUnknown;
-        globals.instSource.nixExprPath = getDefNixExprPath();
+        globals.instSource.nixExprPath = getHome() + "/.nix-defexpr";
         globals.instSource.systemFilter = "*";
 
+        if (!pathExists(globals.instSource.nixExprPath)) {
+            createDirs(globals.instSource.nixExprPath);
+            replaceSymlink(
+                fmt("%s/profiles/per-user/%s/channels", settings.nixStateDir, getUserName()),
+                globals.instSource.nixExprPath + "/channels");
+            if (getuid() != 0)
+                replaceSymlink(
+                    fmt("%s/profiles/per-user/root/channels", settings.nixStateDir),
+                    globals.instSource.nixExprPath + "/channels_root");
+        }
+
         globals.dryRun = false;
         globals.preserveInstalled = false;
         globals.removeAll = false;