From e547bd0dc419cdbe2e8d8440224b252f723590ab Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Mon, 19 Mar 2018 18:03:46 -0400
Subject: lib: Factor in tiny bit of `meta.platform` checking

I need it in stdenv and release-lib, so that seems motivation enough.
---
 lib/meta.nix | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

(limited to 'lib/meta.nix')

diff --git a/lib/meta.nix b/lib/meta.nix
index 07b1710fff7..199030c103a 100644
--- a/lib/meta.nix
+++ b/lib/meta.nix
@@ -67,4 +67,23 @@ rec {
   */
   hiPrioSet = set: mapDerivationAttrset hiPrio set;
 
+
+  /* Check to see if a platform is matched by the given `meta.platforms`
+     element.
+
+     A `meta.platform` pattern is either
+
+       1. (legacy) a system string.
+
+       2. (modern) a pattern for the platform `parsed` field.
+
+     We can inject these into a patten for the whole of a structured platform,
+     and then match that.
+  */
+  platformMatch = platform: elem: let
+      pattern =
+        if builtins.isString elem
+        then { system = elem; }
+        else { parsed = elem; };
+    in lib.matchAttrs pattern platform;
 }
-- 
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