From 570aed4b46916551da969c4daeef0322461ac2fe Mon Sep 17 00:00:00 2001
From: Jan Malakhovski <oxij@oxij.org>
Date: Sat, 23 Feb 2019 18:06:51 +0000
Subject: [PATCH] lib: add `showWarnings`

---
 lib/default.nix                               | 2 +-
 lib/trivial.nix                               | 3 ++-
 nixos/modules/system/activation/top-level.nix | 4 +---
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/lib/default.nix b/lib/default.nix
index dbb90081b2c3..688c117d52b4 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -59,7 +59,7 @@ let
       stringLength sub substring tail;
     inherit (trivial) id const concat or and bitAnd bitOr bitXor bitNot
       boolToString mergeAttrs flip mapNullable inNixShell min max
-      importJSON warn info nixpkgsVersion version mod compare
+      importJSON warn info showWarnings nixpkgsVersion version mod compare
       splitByAndCompare functionArgs setFunctionArgs isFunction;
     inherit (fixedPoints) fix fix' converge extends composeExtensions
       makeExtensible makeExtensibleWithCustomName;
diff --git a/lib/trivial.nix b/lib/trivial.nix
index 3f0816b55405..2d682961035f 100644
--- a/lib/trivial.nix
+++ b/lib/trivial.nix
@@ -259,9 +259,10 @@ rec {
   # TODO: figure out a clever way to integrate location information from
   # something like __unsafeGetAttrPos.
 
-  warn = msg: builtins.trace "WARNING: ${msg}";
+  warn = msg: builtins.trace "warning: ${msg}";
   info = msg: builtins.trace "INFO: ${msg}";
 
+  showWarnings = warnings: res: lib.fold (w: x: warn w x) res warnings;
 
   ## Function annotations
 
diff --git a/nixos/modules/system/activation/top-level.nix b/nixos/modules/system/activation/top-level.nix
index a560af5ce96d..5c88d27b6c65 100644
--- a/nixos/modules/system/activation/top-level.nix
+++ b/nixos/modules/system/activation/top-level.nix
@@ -130,11 +130,9 @@ let
 
   failedAssertions = map (x: x.message) (filter (x: !x.assertion) config.assertions);
 
-  showWarnings = res: fold (w: x: builtins.trace "warning: ${w}" x) res config.warnings;
-
   baseSystemAssertWarn = if failedAssertions != []
     then throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failedAssertions)}"
-    else showWarnings baseSystem;
+    else showWarnings config.warnings baseSystem;
 
   # Replace runtime dependencies
   system = fold ({ oldDependency, newDependency }: drv: