Add a test ensuring compatibility with an old daemon

This requires adding `nix` to its own closure which is a bit unfortunate,
but as it is optional (the test will be disabled if `OUTER_NIX` is unset) it
shouldn't be too much of an issue.

(Ideally this should go in another derivation so that we can build Nix and run
the test independently, but as the tests are running in the same derivation
as the build it's a bit complicated to do so).

5 files changed, 20 insertions, 5 deletions

diff --git a/flake.nix b/flake.nix
index e59ec9a35..3e236aaca 100644
--- a/flake.nix
+++ b/flake.nix
@@ -150,6 +150,11 @@
       # 'nix.perl-bindings' packages.
       overlay = final: prev: {
 
+        # An older version of Nix to test against when using the daemon.
+        # Currently using `nixUnstable` as the stable one doesn't respect
+        # `NIX_DAEMON_SOCKET_PATH` which is needed for the tests.
+        mainstream-nix = prev.nixUnstable;
+
         nix = with final; with commonDeps pkgs; stdenv.mkDerivation {
           name = "nix-${version}";
           inherit version;
@@ -158,6 +163,8 @@
 
           VERSION_SUFFIX = versionSuffix;
 
+          OUTER_NIX = mainstream-nix;
+
           outputs = [ "out" "dev" "doc" ];
 
           nativeBuildInputs = nativeBuildDeps;
@@ -486,6 +493,8 @@
         stdenv.mkDerivation {
           name = "nix";
 
+          OUTER_NIX = mainstream-nix;
+
           outputs = [ "out" "dev" "doc" ];
 
           nativeBuildInputs = nativeBuildDeps;
diff --git a/tests/common.sh.in b/tests/common.sh.in
index de44a4da4..277dd6dfa 100644
--- a/tests/common.sh.in
+++ b/tests/common.sh.in
@@ -57,7 +57,6 @@ clearStore() {
     mkdir "$NIX_STORE_DIR"
     rm -rf "$NIX_STATE_DIR"
     mkdir "$NIX_STATE_DIR"
-    nix-store --init
     clearProfiles
 }
 
@@ -73,7 +72,7 @@ startDaemon() {
     # Start the daemon, wait for the socket to appear.  !!!
     # ‘nix-daemon’ should have an option to fork into the background.
     rm -f $NIX_STATE_DIR/daemon-socket/socket
-    nix daemon &
+    ${NIX_DAEMON_COMMAND:-nix daemon} &
     for ((i = 0; i < 30; i++)); do
         if [ -e $NIX_DAEMON_SOCKET_PATH ]; then break; fi
         sleep 1
diff --git a/tests/local.mk b/tests/local.mk
index de095c117..dd9a0ad56 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -6,7 +6,7 @@ nix_tests = \
   gc-auto.sh \
   referrers.sh user-envs.sh logging.sh nix-build.sh misc.sh fixed.sh \
   gc-runtime.sh check-refs.sh filter-source.sh \
-  local-store.sh remote-store.sh export.sh export-graph.sh \
+  local-store.sh remote-store.sh remote-store-old-daemon.sh export.sh export-graph.sh \
   timeout.sh secure-drv-outputs.sh nix-channel.sh \
   multiple-outputs.sh import-derivation.sh fetchurl.sh optimise-store.sh \
   binary-cache.sh \
diff --git a/tests/remote-store-old-daemon.sh b/tests/remote-store-old-daemon.sh
new file mode 100644
index 000000000..ede7ce716
--- /dev/null
+++ b/tests/remote-store-old-daemon.sh
@@ -0,0 +1,7 @@
+# Test that the new Nix can properly talk to an old daemon.
+# If `$OUTER_NIX` isn't set (e.g. when bootsraping), just skip this test
+
+if [[ -n "$OUTER_NIX" ]]; then
+    export NIX_DAEMON_COMMAND=$OUTER_NIX/bin/nix-daemon
+    source remote-store.sh
+fi
diff --git a/tests/remote-store.sh b/tests/remote-store.sh
index f7ae1a2ed..31210ab47 100644
--- a/tests/remote-store.sh
+++ b/tests/remote-store.sh
@@ -23,12 +23,12 @@ startDaemon
 
 storeCleared=1 NIX_REMOTE_=$NIX_REMOTE $SHELL ./user-envs.sh
 
+nix-store --gc --max-freed 1K
+
 nix-store --dump-db > $TEST_ROOT/d1
 NIX_REMOTE= nix-store --dump-db > $TEST_ROOT/d2
 cmp $TEST_ROOT/d1 $TEST_ROOT/d2
 
-nix-store --gc --max-freed 1K
-
 killDaemon
 
 user=$(whoami)