home-environment: prepend instead of append

modules/home-environment.nix

@@ -309,7 +309,7 @@ in
         ".git/safe/../../bin"
       ];
       description = ''
-        Extra directories to add to {env}`PATH`.
+        Extra directories to be prepend to {env}`PATH`.
 
         These directories are added to the {env}`PATH` variable in a
         double-quoted context, so expressions like `$HOME` are
@@ -329,9 +329,9 @@ in
         ];
       };
       description = ''
-        Extra directories to add to arbitrary PATH-like environment
-        variables (e.g.: {env}`MANPATH`). The values will be concatenated
-        by `:`.
+        Extra directories to be prepend to arbitrary PATH-like
+        environment variables (e.g.: {env}`MANPATH`). The values
+        will be concatenated by `:`.
 
         These directories are added to the environment variable in a
         double-quoted context, so expressions like `$HOME` are
@@ -581,7 +581,7 @@ in
         (mapAttrsToList
           (env: values: config.lib.shell.export
             env
-            (config.lib.shell.appendToVar ":" env values))
+            (config.lib.shell.prependToVar ":" env values))
           cfg.sessionSearchVariables)
         + cfg.sessionVariablesExtra;
     };

modules/lib/shell.nix

@@ -1,13 +1,13 @@
 { lib }:
 
 rec {
-  # Produces a Bourne shell like statement that appends new values to
+  # Produces a Bourne shell like statement that prepend new values to
   # an possibly existing variable, using sep(ator).
   # Example:
-  #   appendToVar ":" "PATH" [ "$HOME/bin" "$HOME/.local/bin" ]
-  #   => "$PATH\${PATH:+:}$HOME/bin:$HOME/.local/bin"
-  appendToVar = sep: n: v:
-    "\$${n}\${${n}:+${sep}}${lib.concatStringsSep sep v}";
+  #   prependToVar ":" "PATH" [ "$HOME/bin" "$HOME/.local/bin" ]
+  #   => "$HOME/bin:$HOME/.local/bin:${PATH:+:}\$PATH"
+  prependToVar = sep: n: v:
+    "${lib.concatStringsSep sep v}\${${n}:+${sep}}\$${n}";
 
   # Produces a Bourne shell like variable export statement.
   export = n: v: ''export ${n}="${toString v}"'';

tests/modules/home-environment/session-path.nix

@@ -10,6 +10,6 @@
     hmSessVars=home-path/etc/profile.d/hm-session-vars.sh
     assertFileExists $hmSessVars
     assertFileContains $hmSessVars \
-      'export PATH="$PATH''${PATH:+:}bar:baz:foo"'
+      'export PATH="bar:baz:foo''${PATH:+:}$PATH"'
   '';
 }

tests/modules/home-environment/session-search-variables.nix

@@ -10,6 +10,6 @@
     hmSessVars=home-path/etc/profile.d/hm-session-vars.sh
     assertFileExists $hmSessVars
     assertFileContains $hmSessVars \
-      'export TEST="$TEST''${TEST:+:}bar:baz:foo"'
+      'export TEST="bar:baz:foo''${TEST:+:}$TEST"'
   '';
 }