From eb68454be61bd6e8baf40136ae69c2b5fec3006a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Wed, 4 Oct 2023 17:10:54 +0200
Subject: [PATCH 1/2] Don't run the tests that require building if we're not
 building

A couple of tests require building some libraries that depend on Nix,
and assume it to be built locally.
Don't run these if we only want to run the install tests.

This prevents the CI from rebuilding several times Nix (like in
https://github.com/NixOS/nix/actions/runs/6404422275/job/17384964033#step:6:6412), thus removing a fair amount of build time.
---
 flake.nix      |  1 +
 tests/local.mk | 24 ++++++++++++++++--------
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/flake.nix b/flake.nix
index e3b9477a5..d74085db7 100644
--- a/flake.nix
+++ b/flake.nix
@@ -260,6 +260,7 @@
       testNixVersions = pkgs: client: daemon: with commonDeps { inherit pkgs; }; with pkgs.lib; pkgs.stdenv.mkDerivation {
         NIX_DAEMON_PACKAGE = daemon;
         NIX_CLIENT_PACKAGE = client;
+        HAVE_LOCAL_NIX_BUILD = false;
         name =
           "nix-tests"
           + optionalString
diff --git a/tests/local.mk b/tests/local.mk
index 7479b1576..ac418dc0d 100644
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -1,3 +1,7 @@
+# whether to run the tests that assume that we have a local build of
+# Nix
+HAVE_LOCAL_NIX_BUILD ?= 1
+
 nix_tests = \
   test-infra.sh \
   init.sh \
@@ -104,7 +108,6 @@ nix_tests = \
   case-hack.sh \
   placeholders.sh \
   ssh-relay.sh \
-  plugins.sh \
   build.sh \
   build-delete.sh \
   output-normalization.sh \
@@ -120,7 +123,6 @@ nix_tests = \
   flakes/show.sh \
   impure-derivations.sh \
   path-from-hash-part.sh \
-  test-libstoreconsumer.sh \
   toString-path.sh \
   read-only-store.sh \
   nested-sandboxing.sh
@@ -129,6 +131,17 @@ ifeq ($(HAVE_LIBCPUID), 1)
 	nix_tests += compute-levels.sh
 endif
 
+ifeq ($(HAVE_LOCAL_NIX_BUILD), 1)
+	nix_tests += test-libstoreconsumer.sh
+
+	ifeq ($(BUILD_SHARED_LIBS), 1)
+		nix_tests += plugins.sh
+	endif
+endif
+
+tests/test-libstoreconsumer.sh.test: tests/test-libstoreconsumer/test-libstoreconsumer
+tests/plugins.sh: tests/plugins/libplugintest.$(SO_EXT)
+
 install-tests += $(foreach x, $(nix_tests), $(d)/$(x))
 
 clean-files += \
@@ -137,9 +150,4 @@ clean-files += \
 
 test-deps += \
   tests/common/vars-and-functions.sh \
-  tests/config.nix \
-  tests/test-libstoreconsumer/test-libstoreconsumer
-
-ifeq ($(BUILD_SHARED_LIBS), 1)
-  test-deps += tests/plugins/libplugintest.$(SO_EXT)
-endif
+  tests/config.nix

From 92e8e1b1bbc59d3a7e9efd5bff146b0a2726c7b9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Th=C3=A9ophane=20Hufschmitt?=
 <theophane.hufschmitt@tweag.io>
Date: Wed, 4 Oct 2023 17:22:45 +0200
Subject: [PATCH 2/2] Poison the build on the test derivation

Make sure that we're not accidentally rebuilding Nix here as it's just
wasteful and awful for CI times.
---
 flake.nix | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/flake.nix b/flake.nix
index d74085db7..4de155362 100644
--- a/flake.nix
+++ b/flake.nix
@@ -280,9 +280,13 @@
         enableParallelBuilding = true;
 
         configureFlags = testConfigureFlags; # otherwise configure fails
-        dontBuild = true;
         doInstallCheck = true;
 
+        buildPhase = ''
+          # Remove the source files to make sure that we're not accidentally rebuilding Nix
+          rm src/**/*.cc
+        '';
+
         installPhase = ''
           mkdir -p $out
         '';