allow exposeModules to be shared

lib/exposeModules.nix

@@ -0,0 +1,35 @@
+let
+  inherit (builtins)
+    listToAttrs
+    replaceStrings
+    stringLength
+    substring
+    ;
+
+  removeSuffix =
+    # Suffix to remove if it matches
+    suffix:
+    # Input string
+    str:
+    let
+      sufLen = stringLength suffix;
+      sLen = stringLength str;
+    in
+    if sufLen <= sLen && suffix == substring (sLen - sufLen) sufLen str then
+      substring 0 (sLen - sufLen) str
+    else
+      str;
+in
+# Map 1:1 between paths and modules
+baseDir: paths:
+let
+  prefix = stringLength (toString baseDir) + 1;
+
+  toPair = path: {
+    name = replaceStrings [ "/" ] [ "-" ] (
+      removeSuffix ".nix" (substring prefix 1000000 (toString path))
+    );
+    value = path;
+  };
+in
+listToAttrs (map toPair paths)

nixos/default.nix

@@ -1,39 +1,5 @@
 let
-  inherit (builtins)
-    listToAttrs
-    replaceStrings
-    stringLength
-    substring
-    ;
-
-  removeSuffix =
-    # Suffix to remove if it matches
-    suffix:
-    # Input string
-    str:
-    let
-      sufLen = stringLength suffix;
-      sLen = stringLength str;
-    in
-    if sufLen <= sLen && suffix == substring (sLen - sufLen) sufLen str then
-      substring 0 (sLen - sufLen) str
-    else
-      str;
-
-  # Map 1:1 between paths and modules
-  exposeModules = baseDir: paths:
-    let
-      prefix = stringLength (toString baseDir) + 1;
-
-      toPair = path: {
-        name = replaceStrings [ "/" ] [ "-" ] (removeSuffix ".nix" (substring prefix 1000000
-          (toString path)));
-        value = path;
-      };
-    in
-    listToAttrs (map toPair paths)
-  ;
-
+  exposeModules = import ../lib/exposeModules.nix;
 in
 exposeModules ./. [
   ./common