From 8c0416ef364f5d5dea9d5694aadc0014bb95c1ca Mon Sep 17 00:00:00 2001
From: Adam Joseph <adam@westernsemico.com>
Date: Mon, 21 Aug 2023 14:38:53 -0700
Subject: [PATCH] lib.systems.inspect: add patternLogicalAnd

---
 lib/systems/inspect.nix | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/lib/systems/inspect.nix b/lib/systems/inspect.nix
index 022e459c3945..073df78797c7 100644
--- a/lib/systems/inspect.nix
+++ b/lib/systems/inspect.nix
@@ -100,6 +100,32 @@ rec {
     ];
   };
 
+  # given two patterns, return a pattern which is their logical AND.
+  # Since a pattern is a list-of-disjuncts, this needs to
+  patternLogicalAnd = pat1_: pat2_:
+    let
+      # patterns can be either a list or a (bare) singleton; turn
+      # them into singletons for uniform handling
+      pat1 = lib.toList pat1_;
+      pat2 = lib.toList pat2_;
+    in
+      lib.concatMap (attr1:
+        map (attr2:
+          lib.recursiveUpdateUntil
+            (path: subattr1: subattr2:
+              if (builtins.intersectAttrs subattr1 subattr2) == {} || subattr1 == subattr2
+              then true
+              else throw ''
+                pattern conflict at path ${toString path}:
+                  ${builtins.toJSON subattr1}
+                  ${builtins.toJSON subattr2}
+                '')
+            attr1
+            attr2
+            )
+          pat2)
+        pat1;
+
   matchAnyAttrs = patterns:
     if builtins.isList patterns then attrs: any (pattern: matchAttrs pattern attrs) patterns
     else matchAttrs patterns;