From 2a170f1ed744b2e80973fe58c8a68885fd1510bb Mon Sep 17 00:00:00 2001
From: Vincent Ambo <Vincent Ambo>
Date: Thu, 9 Jan 2020 00:46:20 +0000
Subject: fix(buildLisp): Perform a topological sort of dependencies

This ensures that dependencies are loaded in the correct order in
larger dependency graphs.
---
 nix/buildLisp/default.nix | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

(limited to 'nix/buildLisp')

diff --git a/nix/buildLisp/default.nix b/nix/buildLisp/default.nix
index e8d235df7c..15dddfbbab 100644
--- a/nix/buildLisp/default.nix
+++ b/nix/buildLisp/default.nix
@@ -61,15 +61,14 @@ let
         ))
   '';
 
+  # 'dependsOn' determines whether Lisp library 'b' depends on 'a'.
+  dependsOn = a: b: builtins.elem a b.lispDeps;
+
   # 'allDeps' flattens the list of dependencies (and their
-  # dependencies) into one list of unique deps.
-  #
-  # TODO(tazjin): Ordering needs to be stable (first occurences from
-  # innermost to outer), I don't know if this works accidentally or is
-  # guaranteed by these lib functions.
-  allDeps = deps: lib.reverseList (
-    lib.unique (lib.flatten (deps ++ (map (d: d.lispDeps) deps)))
-  );
+  # dependencies) into one ordered list of unique deps.
+  allDeps = deps: (lib.toposort dependsOn (lib.unique (
+    lib.flatten (deps ++ (map (d: d.lispDeps) deps))
+  ))).result;
 
   # 'genDumpLisp' generates a Lisp file that instructs SBCL to dump
   # the currently loaded image as an executable to $out/bin/$name.
-- 
cgit 1.4.1