lib.systems: deprecate == comparison between elaborated platforms

doc/release-notes/rl-2505.section.md

@@ -41,6 +41,10 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
+- Using `==` or `!=` to compare elaborated platform attrsets, such as `stdenv.hostPlatform` and `stdenv.buildPlatform`, is no longer supported and may produce a warning. In a future version, this warning will be replaced with an error. Instead, you should use the `canExecute`, `equals`, or `notEquals` functions included with platform attrsets or use `lib.systems.equals`.
+
+  - E.g. replace `hostPlatform == buildPlatform` with `buildPlatform.canExecute hostPlatform`.
+
 - `apptainer` and `singularity` deprecate the workaround of overriding `vendorHash` and related attributes via `<pkg>.override`,
   in favour of the unified overriding of the same group of attributes via `<pkg>.overrideAttrs`.
   The compatibility layer will be removed in future releases.

lib/systems/default.nix

@@ -20,6 +20,15 @@ let
 
   inherit (lib.strings) toJSON;
 
+  # define this binding in the top-level let-block so that it only prints once
+  warnAboutPlatformEquals = lib.warn (lib.concatStringsSep " " [
+    "It seems that you're comparing platform attrsets using plain == equality,"
+    "which is not supported, and will result in an error soon."
+    "Use `--abort-on-warn --show-trace` to find the location of this warning."
+    "If equality (e.g. host == build) was used, try (build.canExecute host) or (build.equals host) instead."
+    "If equality was not used, you may avoid this warning by filtering out the `warnAboutPlatformEquals` attribute."
+  ]) null;
+
   doubles = import ./doubles.nix { inherit lib; };
   parse = import ./parse.nix { inherit lib; };
   inspect = import ./inspect.nix { inherit lib; };
@@ -43,9 +52,9 @@ let
   */
   equals =
     let
-      removeFunctions = a: filterAttrs (_: v: !isFunction v) a;
+      removeUnwanted = filterAttrs (name: v: !(name == "warnAboutPlatformEquals" || isFunction v));
     in
-    a: b: removeFunctions a == removeFunctions b;
+    a: b: removeUnwanted a == removeUnwanted b;
 
   /**
     List of all Nix system doubles the nixpkgs flake will expose the package set
@@ -531,6 +540,11 @@ let
               "-uefi"
             ];
           };
+        }
+        // {
+          inherit warnAboutPlatformEquals;
+          equals = equals final;
+          notEquals = platform: !final.equals platform;
         };
     in
     assert final.useAndroidPrebuilt -> final.isAndroid;

lib/tests/systems.nix

@@ -267,21 +267,24 @@ lib.runTests (
           in
           {
             expr = lib.systems.equals (lib.systems.elaborate "x86_64-linux") modified;
-            expected =
-              {
-                # Changes in these attrs are not detectable because they're function.
-                # The functions should be derived from the data, so this is not a problem.
-                canExecute = null;
-                emulator = null;
-                emulatorAvailable = null;
-                staticEmulatorAvailable = null;
-                isCompatible = null;
-              } ? ${platformAttrName};
+            expected = false;
           };
-
       })
+      # x86_64-linux is an arbitrary choice, just to get all the elaborated attrNames
       (
-        lib.systems.elaborate "x86_64-linux" # arbitrary choice, just to get all the elaborated attrNames
+        builtins.removeAttrs (lib.systems.elaborate "x86_64-linux") [
+          # Avoid the warning
+          "warnAboutPlatformEquals"
+          # Changes in these attrs are not detectable because they're function.
+          # The functions should be derived from the data, so this is not a problem.
+          "canExecute"
+          "emulator"
+          "emulatorAvailable"
+          "equals"
+          "isCompatible"
+          "notEquals"
+          "staticEmulatorAvailable"
+        ]
       )
 
 )

nixos/modules/config/nix.nix

@@ -145,7 +145,7 @@ let
         ${cfg.extraOptions}
       '';
       checkPhase = lib.optionalString cfg.checkConfig (
-        if pkgs.stdenv.hostPlatform != pkgs.stdenv.buildPlatform then
+        if pkgs.stdenv.hostPlatform.notEquals pkgs.stdenv.buildPlatform then
           ''
             echo "Ignoring validation for cross-compilation"
           ''

nixos/modules/misc/nixpkgs.nix

@@ -73,7 +73,7 @@ let
   defaultPkgs =
     if opt.hostPlatform.isDefined then
       let
-        isCross = cfg.buildPlatform != cfg.hostPlatform;
+        isCross = cfg.buildPlatform.notEquals cfg.hostPlatform;
         systemArgs =
           if isCross then
             {
@@ -226,7 +226,15 @@ in
           elaborated = lib.systems.elaborate inputBuildPlatform;
         in
         if lib.systems.equals elaborated cfg.hostPlatform then
-          cfg.hostPlatform # make identical, so that `==` equality works; see https://github.com/NixOS/nixpkgs/issues/278001
+          # Make equivalent platforms actually identical, so that `==` equality works.
+          # See https://github.com/NixOS/nixpkgs/issues/278001
+          # NOTE: `==` between platforms was deprecated 2025-02-08.
+          # Users should instead use the `canExecute`, `equals`, or `notEquals`
+          # functions included with platform attrsets or use `lib.systems.equals`.
+          # See https://github.com/NixOS/nixpkgs/pull/380005
+          # TODO: Once users have had chance to migrate, this `apply` function
+          # can be simplified to `lib.systems.elaborate`.
+          cfg.hostPlatform
         else
           elaborated;
       defaultText = lib.literalExpression ''config.nixpkgs.hostPlatform'';

nixos/modules/services/databases/postgresql.nix

@@ -715,7 +715,7 @@ in
     ];
 
     system.checks = lib.optional (
-      cfg.checkConfig && pkgs.stdenv.hostPlatform == pkgs.stdenv.buildPlatform
+      cfg.checkConfig && pkgs.stdenv.hostPlatform.equals pkgs.stdenv.buildPlatform
     ) configFileCheck;
 
     systemd.services.postgresql = {

nixos/modules/services/monitoring/nagios.nix

@@ -139,8 +139,8 @@ in
 
       validateConfig = lib.mkOption {
         type = lib.types.bool;
-        default = pkgs.stdenv.hostPlatform == pkgs.stdenv.buildPlatform;
-        defaultText = lib.literalExpression "pkgs.stdenv.hostPlatform == pkgs.stdenv.buildPlatform";
+        default = pkgs.stdenv.hostPlatform.equals pkgs.stdenv.buildPlatform;
+        defaultText = lib.literalExpression "pkgs.stdenv.hostPlatform.equals pkgs.stdenv.buildPlatform";
         description = "if true, the syntax of the nagios configuration file is checked at build time";
       };
 

nixos/modules/services/networking/ssh/sshd.nix

@@ -11,7 +11,7 @@ let
   # This middle-ground solution ensures *an* sshd can do their basic validation
   # on the configuration.
   validationPackage =
-    if pkgs.stdenv.buildPlatform == pkgs.stdenv.hostPlatform then
+    if pkgs.stdenv.buildPlatform.equals pkgs.stdenv.hostPlatform then
       cfg.package
     else
       pkgs.buildPackages.openssh;

nixos/modules/services/web-servers/caddy/default.nix

@@ -60,7 +60,7 @@ let
         '';
       in
       "${
-        if pkgs.stdenv.buildPlatform == pkgs.stdenv.hostPlatform then Caddyfile-formatted else Caddyfile
+        if pkgs.stdenv.buildPlatform.equals pkgs.stdenv.hostPlatform then Caddyfile-formatted else Caddyfile
       }/Caddyfile";
 
   etcConfigFile = "caddy/caddy_config";

nixos/modules/system/activation/switchable-system.nix

@@ -71,7 +71,7 @@ in
           ;
 
         chmod +x $out/bin/switch-to-configuration
-        ${lib.optionalString (pkgs.stdenv.hostPlatform == pkgs.stdenv.buildPlatform) ''
+        ${lib.optionalString (pkgs.stdenv.hostPlatform.equals pkgs.stdenv.buildPlatform) ''
           if ! output=$(${perlWrapped}/bin/perl -c $out/bin/switch-to-configuration 2>&1); then
             echo "switch-to-configuration syntax is not valid:"
             echo "$output"

nixos/modules/system/boot/stage-1.nix

@@ -221,7 +221,7 @@ let
           patchelf --set-rpath $out/lib $i
         done
 
-        if [ -z "${toString (pkgs.stdenv.hostPlatform != pkgs.stdenv.buildPlatform)}" ]; then
+        if [ -z "${toString (pkgs.stdenv.hostPlatform.notEquals pkgs.stdenv.buildPlatform)}" ]; then
         # Make sure that the patchelf'ed binaries still work.
         echo "testing patched programs..."
         $out/bin/ash -c 'echo hello world' | grep "hello world"

pkgs/applications/audio/csound/default.nix

@@ -44,9 +44,7 @@ stdenv.mkDerivation {
     [ "-DBUILD_CSOUND_AC=0" ] # fails to find Score.hpp
     ++ lib.optional stdenv.hostPlatform.isDarwin "-DCS_FRAMEWORK_DEST=${placeholder "out"}/lib"
     # Ignore gettext in CMAKE_PREFIX_PATH on cross to prevent find_program picking up the wrong gettext
-    ++ lib.optional (
-      stdenv.hostPlatform != stdenv.buildPlatform
-    ) "-DCMAKE_IGNORE_PATH=${lib.getBin gettext}/bin";
+    ++ lib.optional (stdenv.hostPlatform.notEquals stdenv.buildPlatform) "-DCMAKE_IGNORE_PATH=${lib.getBin gettext}/bin";
 
   nativeBuildInputs = [
     cmake

pkgs/applications/audio/faust/faust2.nix

@@ -92,11 +92,9 @@ let
         cd ..
         shopt -s globstar
         for f in **/Makefile **/Makefile.library **/CMakeLists.txt build/Make.llvm.static embedded/faustjava/faust2engine architecture/autodiff/autodiff.sh source/tools/faust2appls/* **/llvm.cmake tools/benchmark/faust2object; do
-          echo $f "llvm-config${lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) "-native"}"
+          echo $f "llvm-config${lib.optionalString (stdenv.hostPlatform.notEquals stdenv.buildPlatform) "-native"}"
           substituteInPlace $f \
-            --replace-quiet "llvm-config" "llvm-config${
-              lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) "-native"
-            }"
+            --replace-quiet "llvm-config" "llvm-config${lib.optionalString (stdenv.hostPlatform.notEquals stdenv.buildPlatform) "-native"}"
         done
         shopt -u globstar
         cd build

pkgs/applications/editors/vim/default.nix

@@ -59,7 +59,7 @@ stdenv.mkDerivation {
       "--enable-multibyte"
       "--enable-nls"
     ]
-    ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) (
+    ++ lib.optionals (stdenv.hostPlatform.notEquals stdenv.buildPlatform) (
       [
         "vim_cv_toupper_broken=no"
         "--with-tlib=ncurses"

pkgs/applications/editors/vim/full.nix

@@ -129,7 +129,7 @@ stdenv.mkDerivation {
       "--disable-carbon_check"
       "--disable-gtktest"
     ]
-    ++ lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+    ++ lib.optionals (stdenv.hostPlatform.notEquals stdenv.buildPlatform) [
       "vim_cv_toupper_broken=no"
       "--with-tlib=ncurses"
       "vim_cv_terminfo=yes"

pkgs/applications/graphics/sane/backends/default.nix

@@ -123,7 +123,7 @@ stdenv.mkDerivation rec {
 
   # autoconf check for HAVE_MMAP is never set on cross compilation.
   # The pieusb backend fails compilation if HAVE_MMAP is not set.
-  buildFlags = lib.optionals (stdenv.hostPlatform != stdenv.buildPlatform) [
+  buildFlags = lib.optionals (stdenv.hostPlatform.notEquals stdenv.buildPlatform) [
     "CFLAGS=-DHAVE_MMAP=${if stdenv.hostPlatform.isLinux then "1" else "0"}"
   ];
 

pkgs/applications/networking/browsers/chromium/common.nix

@@ -692,7 +692,8 @@ let
 
       ''
       +
-        lib.optionalString (stdenv.hostPlatform == stdenv.buildPlatform && stdenv.hostPlatform.isAarch64)
+        lib.optionalString
+          (stdenv.hostPlatform.equals stdenv.buildPlatform && stdenv.hostPlatform.isAarch64)
           ''
             substituteInPlace build/toolchain/linux/BUILD.gn \
               --replace 'toolprefix = "aarch64-linux-gnu-"' 'toolprefix = ""'
@@ -739,7 +740,7 @@ let
         # We only build those specific toolchains when we cross-compile, as native non-cross-compilations would otherwise
         # end up building much more things than they need to (roughly double the build steps and time/compute):
       }
-      // lib.optionalAttrs (stdenv.buildPlatform != stdenv.hostPlatform) {
+      // lib.optionalAttrs (stdenv.buildPlatform.notEquals stdenv.hostPlatform) {
         host_toolchain = "//build/toolchain/linux/unbundle:host";
         v8_snapshot_toolchain = "//build/toolchain/linux/unbundle:host";
       }

pkgs/applications/networking/browsers/elinks/default.nix

@@ -23,7 +23,7 @@
   guile ? null,
   enablePython ? false,
   python ? null,
-  enablePerl ? (!stdenv.hostPlatform.isDarwin) && (stdenv.hostPlatform == stdenv.buildPlatform),
+  enablePerl ? (!stdenv.hostPlatform.isDarwin) && (stdenv.hostPlatform.equals stdenv.buildPlatform),
   perl ? null,
 # re-add javascript support when upstream supports modern spidermonkey
 }:

pkgs/applications/networking/browsers/firefox/common.nix

@@ -131,7 +131,7 @@ in
   ),
   overrideCC,
   buildPackages,
-  pgoSupport ? (stdenv.hostPlatform.isLinux && stdenv.hostPlatform == stdenv.buildPlatform),
+  pgoSupport ? (stdenv.hostPlatform.isLinux && stdenv.hostPlatform.equals stdenv.buildPlatform),
   xvfb-run,
   elfhackSupport ?
     isElfhackPlatform stdenv && !(stdenv.hostPlatform.isMusl && stdenv.hostPlatform.isAarch64),

pkgs/applications/networking/sniffers/wireshark/default.nix

@@ -76,7 +76,7 @@ stdenv.mkDerivation rec {
     ./patches/lookup-dumpcap-in-path.patch
   ];
 
-  depsBuildBuild = lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
+  depsBuildBuild = lib.optionals (stdenv.buildPlatform.notEquals stdenv.hostPlatform) [
     buildPackages.stdenv.cc
   ];
 
@@ -163,7 +163,7 @@ stdenv.mkDerivation rec {
       "-DENABLE_APPLICATION_BUNDLE=${if isAppBundle then "ON" else "OFF"}"
       "-DLEMON_C_COMPILER=cc"
     ]
-    ++ lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
+    ++ lib.optionals (stdenv.buildPlatform.notEquals stdenv.hostPlatform) [
       "-DHAVE_C99_VSNPRINTF_EXITCODE__TRYRUN_OUTPUT="
       "-DHAVE_C99_VSNPRINTF_EXITCODE=0"
     ];

pkgs/applications/science/misc/openmodelica/omcompiler/default.nix

@@ -18,7 +18,7 @@
   mkOpenModelicaDerivation,
 }:
 let
-  isCross = stdenv.buildPlatform != stdenv.hostPlatform;
+  isCross = stdenv.buildPlatform.notEquals stdenv.hostPlatform;
   nativeOMCompiler = buildPackages.openmodelica.omcompiler;
 in
 mkOpenModelicaDerivation (

pkgs/applications/version-management/git/default.nix

@@ -33,7 +33,7 @@
   subversionClient,
   perlLibs,
   smtpPerlLibs,
-  perlSupport ? stdenv.buildPlatform == stdenv.hostPlatform,
+  perlSupport ? stdenv.buildPlatform.equals stdenv.hostPlatform,
   nlsSupport ? true,
   osxkeychainSupport ? stdenv.hostPlatform.isDarwin,
   guiSupport ? false,
@@ -178,7 +178,7 @@ stdenv.mkDerivation (finalAttrs: {
     [
       "ac_cv_prog_CURL_CONFIG=${lib.getDev curl}/bin/curl-config"
     ]
-    ++ lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
+    ++ lib.optionals (stdenv.buildPlatform.notEquals stdenv.hostPlatform) [
       "ac_cv_fread_reads_directories=yes"
       "ac_cv_snprintf_returns_bogus=no"
       "ac_cv_iconv_omits_bom=no"
@@ -195,7 +195,7 @@ stdenv.mkDerivation (finalAttrs: {
     ]
     # Git does not allow setting a shell separately for building and run-time.
     # Therefore lets leave it at the default /bin/sh when cross-compiling
-    ++ lib.optional (stdenv.buildPlatform == stdenv.hostPlatform) "SHELL_PATH=${stdenv.shell}"
+    ++ lib.optional (stdenv.buildPlatform.equals stdenv.hostPlatform) "SHELL_PATH=${stdenv.shell}"
     ++ (if perlSupport then [ "PERL_PATH=${perlPackages.perl}/bin/perl" ] else [ "NO_PERL=1" ])
     ++ (if pythonSupport then [ "PYTHON_PATH=${python3}/bin/python" ] else [ "NO_PYTHON=1" ])
     ++ lib.optionals stdenv.hostPlatform.isSunOS [
@@ -219,7 +219,7 @@ stdenv.mkDerivation (finalAttrs: {
     # See https://github.com/Homebrew/homebrew-core/commit/dfa3ccf1e7d3901e371b5140b935839ba9d8b706
     ++ lib.optional stdenv.hostPlatform.isDarwin "TKFRAMEWORK=/nonexistent";
 
-  disallowedReferences = lib.optionals (stdenv.buildPlatform != stdenv.hostPlatform) [
+  disallowedReferences = lib.optionals (stdenv.buildPlatform.notEquals stdenv.hostPlatform) [
     stdenv.shellPackage
   ];
 

pkgs/applications/version-management/mercurial/default.nix

@@ -186,7 +186,7 @@ let
         requiredSystemFeatures = [ "big-parallel" ];
 
         # Don't run tests if not-Linux or if cross-compiling.
-        meta.broken = !stdenv.hostPlatform.isLinux || stdenv.buildPlatform != stdenv.hostPlatform;
+        meta.broken = !stdenv.hostPlatform.isLinux || stdenv.buildPlatform.notEquals stdenv.hostPlatform;
       }
       ''
         addToSearchPathWithCustomDelimiter : PYTHONPATH "${mercurial}/${python.sitePackages}"

pkgs/applications/video/kodi/unwrapped.nix

@@ -410,7 +410,7 @@ stdenv.mkDerivation (finalAttrs: {
     ''
       cmakeFlagsArray+=("-DCORE_PLATFORM_NAME=${lib.concatStringsSep " " kodi_platforms}")
     ''
-    + lib.optionalString (stdenv.hostPlatform != stdenv.buildPlatform) ''
+    + lib.optionalString (stdenv.hostPlatform.notEquals stdenv.buildPlatform) ''
       # Need these tools on the build system when cross compiling,
       # hacky, but have found no other way.
       CXX=$CXX_FOR_BUILD LD=ld make -C tools/depends/native/JsonSchemaBuilder

pkgs/applications/video/mplayer/default.nix

@@ -114,7 +114,7 @@ let
     else
       null;
 
-  crossBuild = stdenv.hostPlatform != stdenv.buildPlatform;
+  crossBuild = stdenv.hostPlatform.notEquals stdenv.buildPlatform;
 
 in
 

pkgs/build-support/bintools-wrapper/default.nix

@@ -107,7 +107,7 @@ let
   #
   # TODO(@Ericson2314) Make unconditional, or optional but always true by
   # default.
-  targetPrefix = optionalString (targetPlatform != hostPlatform) (targetPlatform.config + "-");
+  targetPrefix = optionalString (targetPlatform.notEquals hostPlatform) (targetPlatform.config + "-");
 
   bintoolsVersion = getVersion bintools;
   bintoolsName = removePrefix targetPrefix (getName bintools);