refactor({modules,pkgs}/by-name-overlay): De-duplicate in a `nixLib`

2 files changed, 18 insertions, 79 deletions

diff --git a/pkgs/by-name-overlay.nix b/pkgs/by-name-overlay.nix
deleted file mode 100644
index 7eb3d239..00000000
--- a/pkgs/by-name-overlay.nix
+++ /dev/null
@@ -1,70 +0,0 @@
-# Adapted from this: https://github.com/NixOS/nixpkgs/blob/1814b56453c91192f6d5a6276079948f9fe96c18/pkgs/top-level/by-name-overlay.nix
-{
-  lib,
-  sysLib,
-  pkgs,
-  baseDirectory,
-}:
-# This file turns the pkgs/by-name directory (see its README.md for more info) into an overlay that adds all the defined packages.
-# No validity checks are done here,
-# instead this file is optimised for performance,
-# and validity checks are done by CI on PRs.
-let
-  # FIXME: Check if we override something in the set <2024-05-22>
-  callPackage = lib.callPackageWith (pkgs // myPkgs // {inherit sysLib;});
-  inherit lib;
-
-  inherit
-    (builtins)
-    readDir
-    ;
-
-  inherit
-    (lib.attrsets)
-    mapAttrs
-    mapAttrsToList
-    mergeAttrsList
-    ;
-
-  # Package files for a single shard
-  # Type: String -> String -> AttrsOf Path
-  namesForShard = shard: type:
-    if type != "directory"
-    then
-      # Ignore all non-directories. Technically only README.md is allowed as a file in the base directory, so we could alternatively:
-      # - Assume that README.md is the only file and change the condition to `shard == "README.md"` for a minor performance improvement.
-      #   This would however cause very poor error messages if there's other files.
-      # - Ensure that README.md is the only file, throwing a better error message if that's not the case.
-      #   However this would make for a poor code architecture, because one type of error would have to be duplicated in the validity checks and here.
-      # Additionally in either of those alternatives, we would have to duplicate the hardcoding of "README.md"
-      {}
-    else
-      mapAttrs
-      (name: _: baseDirectory + "/${shard}/${name}/package.nix")
-      (readDir (baseDirectory + "/${shard}"));
-
-  # The attribute set mapping names to the package files defining them
-  # This is defined up here in order to allow reuse of the value (it's kind of expensive to compute)
-  # if the overlay has to be applied multiple times
-  packageFiles = mergeAttrsList (mapAttrsToList namesForShard (readDir baseDirectory));
-  myPkgs =
-    mapAttrs
-    (_: path: callPackage path {})
-    packageFiles;
-in
-  # # TODO: Consider optimising this using `builtins.deepSeq packageFiles`,
-  # # which could free up the above thunks and reduce GC times.
-  # # Currently this would be hard to measure until we have more packages
-  # # and ideally https://github.com/NixOS/nix/pull/8895
-  # self: super:
-  #   {
-  #     # This attribute is necessary to allow CI to ensure that all packages defined in `pkgs/by-name`
-  #     # don't have an overriding definition in `all-packages.nix` with an empty (`{ }`) second `callPackage` argument.
-  #     # It achieves that with an overlay that modifies both `callPackage` and this attribute to signal whether `callPackage` is used
-  #     # and whether it's defined by this file here or `all-packages.nix`.
-  #     # TODO: This can be removed once `pkgs/by-name` can handle custom `callPackage` arguments without `all-packages.nix` (or any other way of achieving the same result).
-  #     # Because at that point the code in ./stage.nix can be changed to not allow definitions in `all-packages.nix` to override ones from `pkgs/by-name` anymore and throw an error if that happens instead.
-  #     _internalCallByNamePackageFile = file: self.callPackage file {};
-  #   }
-  #   //
-  myPkgs
diff --git a/pkgs/default.nix b/pkgs/default.nix
index 66803694..39d225a9 100644
--- a/pkgs/default.nix
+++ b/pkgs/default.nix
@@ -1,13 +1,22 @@
 {
-  pkgs,
-  sysLib,
+  pkgs ? (builtins.getFlake "nixpkgs").legacyPackages."x86_64-linux",
+  sysLib ? builtins.trace "Moking `sysLib`" {},
+  nixLib ? import ../lib {},
 }: let
-  # TODO: Filter the sources of every package in the shards <2024-05-25>
-  files = import ./by-name-overlay.nix {
-    inherit pkgs sysLib;
-    inherit (pkgs) lib;
-    baseDirectory =
-      ./by-name;
+  inherit (pkgs) lib;
+
+  # FIXME: Make this override check actually work.
+  # I think that some parts of the lazy eval are causing that to not actually evaluate the
+  # error message. <2024-10-23>
+  maybeMergeMessage = "While merging the pkgs in ./pkgs/by-name to the nixpkgs set.";
+  mMM = maybeMergeMessage;
+  callPackage = lib.callPackageWith (nixLib.maybeMerge (nixLib.maybeMerge pkgs myPkgs mMM) {inherit sysLib;} mMM);
+
+  myPkgs = nixLib.mkByName {
+    baseDirectory = ./by-name;
+    fileName = "package.nix";
+    finalizeFunction = name: value: callPackage value {};
   };
 in
-  files
+  # TODO: Filter the sources of every package in the shards <2024-05-25>
+  myPkgs