From 6041b78fa45824e23a4db16c6b8e167788a3d179 Mon Sep 17 00:00:00 2001
From: Nicolas Pierron <nicolas.b.pierron@gmail.com>
Date: Sat, 19 Sep 2009 22:10:11 +0000
Subject: [PATCH] Report bad default values which would have cause a build
 failure if they were used to build a NixOS system.

svn path=/nixpkgs/trunk/; revision=17286
---
 pkgs/lib/options.nix | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/pkgs/lib/options.nix b/pkgs/lib/options.nix
index b9ed6e2ec6c..c1c6a64d6d5 100644
--- a/pkgs/lib/options.nix
+++ b/pkgs/lib/options.nix
@@ -235,6 +235,12 @@ rec {
   # the set generated with filterOptionSets.
   optionAttrSetToDocList = ignore: newOptionAttrSetToDocList;
   newOptionAttrSetToDocList = attrs:
+    let tryEval = v:
+      let res = builtins.tryEval v; in
+      if builtins ? tryEval then
+        if res.success then res.value else "<error>"
+      else v;
+    in
     let options = collect isOption attrs; in
       fold (opt: rest:
         let
@@ -246,8 +252,8 @@ rec {
             declarations = map (x: toString x.source) opt.declarations;
             definitions = map (x: toString x.source) opt.definitions;
           }
-          // (if opt ? example then {inherit(opt) example;} else {})
-          // (if opt ? default then {inherit(opt) default;} else {});
+          // optionalAttrs (opt ? example) { example = tryEval opt.example; }
+          // optionalAttrs (opt ? default) { default = tryEval opt.default; };
 
           subOptions =
             if opt ? options then