From a9d3524e1f4f0212184d611b3ff3b520619dff8e Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Wed, 29 May 2019 21:00:44 +0200
Subject: [PATCH] nix flake check: Use read-only mode if we're not building

---
 src/nix/flake.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/nix/flake.cc b/src/nix/flake.cc
index 19e97aed9..0be003da2 100644
--- a/src/nix/flake.cc
+++ b/src/nix/flake.cc
@@ -259,6 +259,8 @@ struct CmdFlakeCheck : FlakeCommand, MixJSON
 
     void run(nix::ref<nix::Store> store) override
     {
+        settings.readOnlyMode = !build;
+
         auto state = getEvalState();
         auto flake = resolveFlake();