Reimplemented how nix finds the lbf modules with new lbf-list-modules.nix

- For some reason, using the `pkgs.lib.*` functions seem to break CI?
  Anyhow, this implementation should a bit more efficient (only by
  constants / without actually measuring) since we don't "append the
  path prefix, then drop the path prefix" i.e., we directly construct
  the module names...

Author: jared

extras/lbf-nix/lbf-list-modules.nix

@@ -0,0 +1,57 @@
+{ lib }:
+# root is the absolute path to the directory with .lbf files. 
+# Example
+# ~~~~~~
+# ```nix
+# let 
+#   lbfListModules = pkgs.callPackage (import ./lbf-list-modules.nix) {};
+# in lbfListModules ./src
+# ```
+# evaluates to
+# ```
+# MySchema
+# Directory.MySchema
+# ```
+# where
+# ```text
+# $ tree src/
+# src/
+# ├── Directory
+# │   └── MySchema.lbf
+# └── MySchema.lbf
+# ```
+
+root:
+# INVARIANT:
+#   - dir == dotPrefix except dotPrefix doesn't contain the prefix root, and
+#   dotPrefix has all `/`s replaced with a singular `.`
+#   - `dotPrefix` always contains the dot at the end if it needs to be there
+let
+  matchLbfFile = name:
+    let matches = builtins.match ''(.*)\.lbf$'' name;
+    in if matches == null
+    then null
+    else builtins.elemAt matches 0;
+
+  go = dir: dotPrefix:
+    builtins.concatLists
+      (lib.mapAttrsToList
+        (name: value:
+          if value == "directory"
+          then go "${dir}/${name}" "${dotPrefix}${name}."
+
+          else if value == "regular"
+          then
+          # Is this an lbf file?
+            let lbfFileMatch = matchLbfFile name;
+            in if lbfFileMatch != null
+            then [ "${dotPrefix}${lbfFileMatch}" ]
+            else [ ]
+          else
+            builtins.trace ''warning: `${name}` has file type `${value}` which is not a regular file nor directory''
+              [ ]
+        )
+        (builtins.readDir dir)
+      );
+in
+go root ""

extras/lbf-nix/lbf-typescript.nix

@@ -85,19 +85,14 @@ let
 
   # TODO(jaredponn): this was (essentially) stolen from the Rust side. This
   # should be made a common function.
-  findModules = root: builtins.map
-    (path: builtins.replaceStrings [ "/" ] [ "." ]
-      (pkgs.lib.strings.removePrefix "./" (pkgs.lib.strings.removeSuffix ".lbf"
-        (pkgs.lib.strings.removePrefix root path))))
-    (builtins.filter (pkgs.lib.hasSuffix ".lbf")
-      (pkgs.lib.filesystem.listFilesRecursive root));
+  lbfListModules = pkgs.callPackage ./lbf-list-modules.nix { };
 
   packageSet =
     pkgs.writeTextFile {
       name = "lb-typescript-packages";
       text =
         builtins.toJSON
-          (builtins.mapAttrs (_name: findModules) imports);
+          (builtins.mapAttrs (_name: lbfListModules) imports);
     };
 
   lbfBuilt = with lbfTypescriptOpts;