From 079be99183243262c68f102955b3479e99b74814 Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Thu, 2 Sep 2021 22:12:54 +0200
Subject: [PATCH] Add lib.generators.toPreserves

---
 .gitignore |  2 ++
 flake.nix  |  6 +++++-
 lib.nix    | 27 +++++++++++++++++++++++++++
 3 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 .gitignore
 create mode 100644 lib.nix

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..750baeb
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+result
+result-*
diff --git a/flake.nix b/flake.nix
index 778acac..ea4c054 100644
--- a/flake.nix
+++ b/flake.nix
@@ -4,11 +4,15 @@
   inputs.rust.url = "github:oxalica/rust-overlay";
 
   outputs = { self, nixpkgs, rust }:
-    let forEachSystem = nixpkgs.lib.genAttrs [ "aarch64-linux" "x86_64-linux" ];
+    let
+      forEachSystem = nixpkgs.lib.genAttrs [ "aarch64-linux" "x86_64-linux" ];
+      libOverlay = import ./lib.nix;
     in {
+      lib = nixpkgs.lib.extend libOverlay;
 
       overlay = final: prev:
         with final; {
+          lib = lib.extend libOverlay;
           syndicate-rs = callPackage ./syndicate-rs {
             rust = rust-bin.nightly.latest.default;
           };
diff --git a/lib.nix b/lib.nix
new file mode 100644
index 0000000..ef84da4
--- /dev/null
+++ b/lib.nix
@@ -0,0 +1,27 @@
+final: prev:
+let lib = final;
+in with lib; {
+
+  generators = with final.generators;
+    prev.generators // {
+      toPreserves = { }@args:
+        v:
+        let concatItems = lib.strings.concatStringsSep " ";
+        in if isAttrs v then
+          "{ ${
+            concatItems (lib.attrsets.mapAttrsToList
+              (key: val: "${key}: ${toPreserves args val}") v)
+          } }"
+        else if isList v then
+          "[ ${concatItems (map (toPreserves args) v)} ]"
+        else if isBool v then
+          (if v then "#t" else "#f")
+        else if isFunction v then
+          abort "generators.toPreserves: cannot convert a function to Preserves"
+        else if isNull v then
+          "null"
+        else
+          builtins.toJSON v;
+    };
+
+}