From fa58bff1ab9aacffd50f8200d72843af7abd827f Mon Sep 17 00:00:00 2001
From: regnat <rg@regnat.ovh>
Date: Mon, 6 Dec 2021 11:45:18 +0100
Subject: [PATCH] Fallback when the daemon is too old for CA derivations

Fix #5712
---
 src/libstore/remote-store.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
index a627e9cf1..c3d23affb 100644
--- a/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -684,6 +684,14 @@ void RemoteStore::queryRealisationUncached(const DrvOutput & id,
     Callback<std::shared_ptr<const Realisation>> callback) noexcept
 {
     auto conn(getConnection());
+
+    if (GET_PROTOCOL_MINOR(conn->daemonVersion) < 27) {
+        warn("The daemon is too old for content-addressed derivations. I’ll do what I can");
+        try {
+            callback(nullptr);
+        } catch (...) { return callback.rethrow(); }
+    }
+
     conn->to << wopQueryRealisation;
     conn->to << id.to_string();
     conn.processStderr();