dhallPackages.generateDhallDirectoryPackage: init

pkgs/development/interpreters/dhall/generate-dhall-directory-package.nix

···
+{ dhall-nixpkgs, lib, stdenv }:
+
+# This function calls `dhall-to-nixpkgs directory --fixed-output-derivations`
+# within a Nix derivation.
+#
+# This is possible because
+# `dhall-to-nixpkgs directory --fixed-output-derivations` will turn remote
+# Dhall imports protected with Dhall integrity checksinto fixed-output
+# derivations (with the `buildDhallUrl` function), so no unrestricted network
+# access is necessary.
+lib.makePackageOverridable
+  ( { src
+    , # The file to import, relative to the root directory
+      file ? "package.dhall"
+    , # Set to `true` to generate documentation for the package
+      document ? false
+    }:
+    stdenv.mkDerivation {
+      name = "dhall-directory-package.nix";
+
+      buildCommand = ''
+        dhall-to-nixpkgs directory --fixed-output-derivations --file "${file}" "${src}" ${if document then "--document" else ""} > $out
+      '';
+
+      nativeBuildInputs = [ dhall-nixpkgs ];
+    }
+  )

pkgs/top-level/dhall-packages.nix

···
       buildDhallUrl =
         callPackage ../development/interpreters/dhall/build-dhall-url.nix { };
 
+      generateDhallDirectoryPackage =
+        callPackage ../development/interpreters/dhall/generate-dhall-directory-package.nix { };
+
     in
       { inherit
           callPackage
···
           buildDhallGitHubPackage
           buildDhallDirectoryPackage
           buildDhallUrl
+          generateDhallDirectoryPackage
         ;
 
         lib = import ../development/dhall-modules/lib.nix { inherit lib; };