From a828cf777aa3497879aeca407af97b652d1edee7 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 5 Nov 2025 15:19:01 +0100
Subject: [PATCH] nix flake check: Remove incorrect assertion

The assumption that no unknown paths can be returned is incorrect. It
can happen if a derivation has outputs that are substitutable, but
that have references that cannot be substituted (i.e. an incomplete
closure in the binary cache). This can easily happen with
magic-nix-cache.
---
 src/nix/flake.cc | 2 --
 1 file changed, 2 deletions(-)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index b826e943c..55112f30f 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -793,8 +793,6 @@ struct CmdFlakeCheck : FlakeCommand
             // via substitution, as `nix flake check` only needs to verify buildability,
             // not actually produce the outputs.
             auto missing = store->queryMissing(drvPaths);
-            // Only occurs if `drvPaths` contains a `DerivedPath::Opaque`, which should never happen
-            assert(missing.unknown.empty());
 
             std::vector<DerivedPath> toBuild;
             for (auto & path : missing.willBuild) {