Use positive source filtering for the standalone functional tests job

Additionally this skipping of the building is reimplemented to be a bit
more robust and use the same idioms as the functionality for skipping
the tests. In particular, it will now work even if the source files
exist, so we can do this during development too.

Makefile

@@ -1,3 +1,7 @@
+-include Makefile.config
+clean-files += Makefile.config
+
+ifeq ($(ENABLE_BUILD), yes)
 makefiles = \
   mk/precompiled-headers.mk \
   local.mk \
@@ -18,15 +22,18 @@ makefiles = \
   misc/upstart/local.mk \
   doc/manual/local.mk \
   doc/internal-api/local.mk
+endif
 
--include Makefile.config
-
-ifeq ($(tests), yes)
+ifeq ($(ENABLE_BUILD)_$(ENABLE_TESTS), yes_yes)
 UNIT_TEST_ENV = _NIX_TEST_UNIT_DATA=unit-test-data
 makefiles += \
   src/libutil/tests/local.mk \
   src/libstore/tests/local.mk \
-  src/libexpr/tests/local.mk \
+  src/libexpr/tests/local.mk
+endif
+
+ifeq ($(ENABLE_TESTS), yes)
+makefiles += \
   tests/functional/local.mk \
   tests/functional/ca/local.mk \
   tests/functional/dyn-drv/local.mk \

Makefile.config.in

@@ -46,5 +46,6 @@ sandbox_shell = @sandbox_shell@
 storedir = @storedir@
 sysconfdir = @sysconfdir@
 system = @system@
-tests = @tests@
+ENABLE_BUILD = @ENABLE_BUILD@
+ENABLE_TESTS = @ENABLE_TESTS@
 internal_api_docs = @internal_api_docs@

configure.ac

@@ -152,12 +152,17 @@ if test "x$GCC_ATOMIC_BUILTINS_NEED_LIBATOMIC" = xyes; then
     LDFLAGS="-latomic $LDFLAGS"
 fi
 
+# Running the functional tests without building Nix is useful for testing
+# different pre-built versions of Nix against each other.
+AC_ARG_ENABLE(build, AS_HELP_STRING([--disable-build],[Do not build nix]),
+  ENABLE_BUILD=$enableval, ENABLE_BUILD=yes)
+AC_SUBST(ENABLE_BUILD)
 # Building without tests is useful for bootstrapping with a smaller footprint
 # or running the tests in a separate derivation. Otherwise, we do compile and
 # run them.
 AC_ARG_ENABLE(tests, AS_HELP_STRING([--disable-tests],[Do not build the tests]),
-  tests=$enableval, tests=yes)
-AC_SUBST(tests)
+  ENABLE_TESTS=$enableval, ENABLE_TESTS=yes)
+AC_SUBST(ENABLE_TESTS)
 
 # Building without API docs is the default as Nix' C++ interfaces are internal and unstable.
 AC_ARG_ENABLE(internal_api_docs, AS_HELP_STRING([--enable-internal-api-docs],[Build API docs for Nix's internal unstable C++ interfaces]),
@@ -289,7 +294,7 @@ if test "$gc" = yes; then
 fi
 
 
-if test "$tests" = yes; then
+if test "$ENABLE_TESTS" = yes; then
 
 # Look for gtest.
 PKG_CHECK_MODULES([GTEST], [gtest_main])

flake.nix

@@ -59,29 +59,40 @@
         # that would interfere with repo semantics.
         fileset.fileFilter (f: f.name != ".gitignore") ./.;
 
+      configureFiles = fileset.unions [
+        ./.version
+        ./configure.ac
+        ./m4
+        # TODO: do we really need README.md? It doesn't seem used in the build.
+        ./README.md
+      ];
+
+      topLevelBuildFiles = fileset.unions [
+        ./local.mk
+        ./Makefile
+        ./Makefile.config.in
+        ./mk
+      ];
+
+      functionalTestFiles = fileset.unions [
+        ./tests/functional
+        (fileset.fileFilter (f: lib.strings.hasPrefix "nix-profile" f.name) ./scripts)
+      ];
+
       nixSrc = fileset.toSource {
         root = ./.;
         fileset = fileset.intersect baseFiles (fileset.unions [
-          ./.version
+          configureFiles
+          topLevelBuildFiles
           ./boehmgc-coroutine-sp-fallback.diff
-          ./bootstrap.sh
-          ./configure.ac
           ./doc
-          ./local.mk
-          ./m4
-          ./Makefile
-          ./Makefile.config.in
           ./misc
-          ./mk
           ./precompiled-headers.h
           ./src
-          ./tests/functional
           ./unit-test-data
           ./COPYING
           ./scripts/local.mk
-          (fileset.fileFilter (f: lib.strings.hasPrefix "nix-profile" f.name) ./scripts)
-          # TODO: do we really need README.md? It doesn't seem used in the build.
-          ./README.md
+          functionalTestFiles
         ]);
       };
 
@@ -252,7 +263,6 @@
       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
@@ -261,7 +271,14 @@
             "-${client.version}-against-${daemon.version}";
         inherit version;
 
-        src = nixSrc;
+        src = fileset.toSource {
+          root = ./.;
+          fileset = fileset.intersect baseFiles (fileset.unions [
+            configureFiles
+            topLevelBuildFiles
+            functionalTestFiles
+          ]);
+        };
 
         VERSION_SUFFIX = versionSuffix;
 
@@ -271,19 +288,20 @@
 
         enableParallelBuilding = true;
 
-        configureFlags = testConfigureFlags; # otherwise configure fails
+        configureFlags =
+          testConfigureFlags # otherwise configure fails
+          ++ [ "--disable-build" ];
+        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
         '';
 
-        installCheckPhase = "make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES";
+        installCheckPhase = ''
+          mkdir -p src/nix-channel
+          make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES
+        '';
       };
 
       binaryTarball = nix: pkgs:

local.mk

@@ -1,5 +1,3 @@
-clean-files += Makefile.config
-
 GLOBAL_CXXFLAGS += -Wno-deprecated-declarations -Werror=switch
 # Allow switch-enum to be overridden for files that do not support it, usually because of dependency headers.
 ERROR_SWITCH_ENUM = -Werror=switch-enum

tests/functional/local.mk

@@ -1,7 +1,3 @@
-# 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 \
@@ -131,7 +127,7 @@ ifeq ($(HAVE_LIBCPUID), 1)
 	nix_tests += compute-levels.sh
 endif
 
-ifeq ($(HAVE_LOCAL_NIX_BUILD), 1)
+ifeq ($(ENABLE_BUILD), yes)
 	nix_tests += test-libstoreconsumer.sh
 
 	ifeq ($(BUILD_SHARED_LIBS), 1)