From b1ca8517ee54b89c24c77af3b9408066cee57d74 Mon Sep 17 00:00:00 2001
From: Jan Malakhovski <oxij@oxij.org>
Date: Mon, 25 Dec 2017 18:06:49 +0000
Subject: [PATCH] lib: generalize `addPassthru` to `extendDerivation`

---
 lib/customisation.nix | 17 +++++++++++++----
 lib/default.nix       |  3 ++-
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/lib/customisation.nix b/lib/customisation.nix
index 483ef6fd486..84f7783a6aa 100644
--- a/lib/customisation.nix
+++ b/lib/customisation.nix
@@ -131,8 +131,8 @@ rec {
 
 
   /* Add attributes to each output of a derivation without changing
-     the derivation itself. */
-  addPassthru = drv: passthru:
+     the derivation itself and check a given condition when evaluating. */
+  extendDerivation = condition: passthru: drv:
     let
       outputs = drv.outputs or [ "out" ];
 
@@ -142,13 +142,22 @@ rec {
       outputToAttrListElement = outputName:
         { name = outputName;
           value = commonAttrs // {
-            inherit (drv.${outputName}) outPath drvPath type outputName;
+            inherit (drv.${outputName}) type outputName;
+            drvPath = assert condition; drv.${outputName}.drvPath;
+            outPath = assert condition; drv.${outputName}.outPath;
           };
         };
 
       outputsList = map outputToAttrListElement outputs;
-  in commonAttrs // { outputUnspecified = true; };
+    in commonAttrs // {
+      outputUnspecified = true;
+      drvPath = assert condition; drv.drvPath;
+      outPath = assert condition; drv.outPath;
+    };
 
+  /* Add attributes to each output of a derivation without changing
+     the derivation itself. */
+  addPassthru = drv: passthru: extendDerivation true passthru drv;
 
   /* Strip a derivation of all non-essential attributes, returning
      only those needed by hydra-eval-jobs. Also strictly evaluate the
diff --git a/lib/default.nix b/lib/default.nix
index 9dc4fea99fc..b304eb62bb2 100644
--- a/lib/default.nix
+++ b/lib/default.nix
@@ -87,7 +87,8 @@ let
     inherit (stringsWithDeps) textClosureList textClosureMap
       noDepEntry fullDepEntry packEntry stringAfter;
     inherit (customisation) overrideDerivation makeOverridable
-      callPackageWith callPackagesWith addPassthru hydraJob makeScope;
+      callPackageWith callPackagesWith extendDerivation addPassthru
+      hydraJob makeScope;
     inherit (meta) addMetaAttrs dontDistribute setName updateName
       appendToName mapDerivationAttrset lowPrio lowPrioSet hiPrio
       hiPrioSet;