Fix :files handling

Exposes what I think is a pre-existing problem with too many directories
getting added to load-path, because we now install a directory
containing a file named "default" that was previously omitted.

cli.el

@@ -12,6 +12,21 @@
          ;; built-in library, which is a Nix store path. We do not want that
          ;; path to escape: avoid it by just filtering ignored packages here.
          (packages (seq-remove (lambda (p) (plist-get (cdr p) :ignore)) packages))
+         ;; For recipes with :files, print it to a string before json-encode.
+         ;; Otherwise it is serialized as a plist if it starts with :defaults.
+         ;; We either ignore this or pass it to melpa2nix in a recipe.
+         (packages
+          (mapcar (lambda (p)
+                    (let* ((plist (cdr p))
+                           (recipe (plist-get plist :recipe))
+                           (files (plist-get recipe :files)))
+                      (when files
+                        (setcdr p
+                                (plist-put plist :recipe
+                                           (plist-put recipe :files
+                                                      (prin1-to-string files)))))
+                      p))
+                  packages))
          (json (json-encode packages))
          (json-path (expand-file-name "packages.json" output-directory)))
     (write-region json nil json-path)))

elisp-packages.nix

@@ -4,6 +4,7 @@
   esuper,
   git,
   makeWrapper,
+  writeText,
 }:
 {
   # Doom uses using emacs-straight/auctex, which still contains parts of
@@ -98,4 +99,35 @@
       description = "build cmake-mode from emacsmirror for Doom";
     };
   };
+  # Doom uses a recipe with :files (:defaults "*"), which MELPA's package-build
+  # rejects because it includes dotfiles
+  # (https://github.com/melpa/package-build/pull/67).
+  # Use a melpaBuild here so the package ends up in its own directory:
+  # it uses that directory as a snippets directory, and using site-lisp/ as that
+  # might go wrong.
+  #
+  # XXX this results in all snippets directories being added to load-path...
+  # This makes a mess (`(load "default")` ends up loading a snippet...).
+  #
+  # Does not look doom-snippets-specific, I also have
+  #
+  # /nix/store/...-emacs-packages-deps/share/emacs/site-lisp/elpa/ansible-20240212.325/snippets/text-mode/ansible/f5
+  #
+  # and so forth.
+  doom-snippets = esuper.melpaBuild {
+    pname = "doom-snippets";
+    version = "1";
+    # melpa2nix requires that we set this. TODO: set correctly.
+    commit = "unset";
+    meta = {
+      description = "trivial build of doom-snippets";
+    };
+    # The directories we want to match must be mode names: assume those are
+    # sensibly named (they currently are).
+    recipe = writeText "doom-snippets-recipe" ''
+      (doom-snippets :fetcher github :repo "doomemacs/snippets"
+                     :files (:defaults "*-mode"))
+    '';
+    packageRequires = [ eself.yasnippet ];
+  };
 }

package.nix

@@ -119,7 +119,7 @@ let
                 # something package.el understands as satisfying dependencies.
                 # This is necessary if we're replacing a pinned ELPA dependency
                 # of an unpinned ELPA package.
-                esuper.melpaBuild ({
+                esuper.melpaBuild {
                   pname = name;
                   # Nix requires that we set version. Inherit it from the
                   # original if available: package.el currently does not check
@@ -132,25 +132,11 @@ let
                     description = "trivial build for doom-emacs";
                   };
                   # Just enough to make melpa2nix work.
-                  # TODO: pass "files" through, drop postUnpack hack below?
-                  recipe = writeText "generated-recipe"
-                    "(${name} :fetcher github :repo \"marienz/made-up\")";
+                  recipe = writeText "generated-recipe" ''
+                    (${name} :fetcher github :repo "marienz/made-up"
+                     ${optionalString (p ? recipe.files) ":files ${lib.debug.traceValSeq p.recipe.files}"})'';
                   buildInputs = (map (name: eself.${name}) reqlist);
-                } // optionalAttrs (p ? recipe.files && p.recipe.files != { defaults = "*"; }) {
-                  # HACK: files can contain :defaults, which splices in defaults.
-                  # If files starts with :defaults, the entire thing gets
-                  # misinterpreted as a proplist when exported to json.
-                  # This currently only happens for `(:defaults "*")`, which we can
-                  # safely ignore (skipping a few excludes).
-                  postUnpack = ''
-                    filteredSrc=$PWD/filteredSrc
-                    mkdir $filteredSrc
-                    pushd $sourceRoot
-                    cp -r ${builtins.toString p.recipe.files} $filteredSrc
-                    popd
-                    sourceRoot=$filteredSrc
-                  '';
-              }));
+                });
             url =
               if (p.recipe.host or "") == "github" && p ? recipe.repo
               then "https://github.com/${p.recipe.repo}"