Improve cross exec platform toolchain selection

.github/workflows/ci.yml

@@ -34,6 +34,8 @@ jobs:
       env:
         GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
       run: bazelisk test //:all_integration_tests
+    - name: Run with extra exec platforms
+      run: bazelisk run //:buildifier --extra_execution_platforms="//:non_host_platform,@platforms//host" '--' -help
 
   example_simple:
     strategy:

BUILD

@@ -58,6 +58,15 @@ alias(
 
 # MARK: - Integration Test
 
+# A platform used for tests that must not match the host platform
+platform(
+    name = "non_host_platform",
+    constraint_values = [
+        "@platforms//os:linux",
+        "@platforms//cpu:riscv64",
+    ],
+)
+
 filegroup(
     name = "local_repository_files",
     srcs = [

MODULE.bazel

@@ -4,6 +4,7 @@ module(
     compatibility_level = 1,
 )
 
+bazel_dep(name = "bazel_features", version = "1.45.0")
 bazel_dep(name = "bazel_skylib", version = "1.3.0")
 bazel_dep(name = "platforms", version = "0.0.11")
 bazel_dep(name = "rules_shell", version = "0.6.1")

buildifier/buildifier_binary.bzl

@@ -2,6 +2,7 @@
 Simple rule for running buildifier from the toolchain config
 """
 
+load("@bazel_features//:features.bzl", "bazel_features")
 load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")
 
 def _buildifier_binary(ctx):
@@ -22,8 +23,11 @@ def _buildifier_binary(ctx):
 
 buildifier_binary = rule(
     implementation = _buildifier_binary,
-    attrs = {},
-    exec_compatible_with = HOST_CONSTRAINTS,
-    toolchains = ["@buildifier_prebuilt//buildifier:toolchain"],
+    exec_compatible_with = [] if bazel_features.toolchains.has_default_test_toolchain_type else HOST_CONSTRAINTS,
+    toolchains = [
+        "@buildifier_prebuilt//buildifier:toolchain",
+    ] + ([
+        "@bazel_tools//tools/test:default_test_toolchain_type",
+    ] if bazel_features.toolchains.has_default_test_toolchain_type else []),
     executable = True,
 )

buildifier/factory.bzl

@@ -142,7 +142,10 @@ def buildifier_impl_factory(ctx, *, test_rule):
             fail("Cannot use 'no_sandbox' without a 'workspace'")
         workspace = ctx.file.workspace.path
 
-    toolchain = ctx.toolchains["@buildifier_prebuilt//buildifier:toolchain"]
+    if test_rule:
+        toolchain = ctx.exec_groups["test"].toolchains["@buildifier_prebuilt//buildifier:toolchain"]
+    else:
+        toolchain = ctx.toolchains["@buildifier_prebuilt//buildifier:toolchain"]
     buildifier = toolchain._tool
     runner = toolchain._runner
 

buildozer/buildozer_binary.bzl

@@ -2,6 +2,7 @@
 Simple rule for running buildozer from the toolchain config
 """
 
+load("@bazel_features//:features.bzl", "bazel_features")
 load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")
 
 def _buildozer_binary(ctx):
@@ -22,8 +23,11 @@ def _buildozer_binary(ctx):
 
 buildozer_binary = rule(
     implementation = _buildozer_binary,
-    attrs = {},
-    exec_compatible_with = HOST_CONSTRAINTS,
-    toolchains = ["@buildifier_prebuilt//buildozer:toolchain"],
+    exec_compatible_with = [] if bazel_features.toolchains.has_default_test_toolchain_type else HOST_CONSTRAINTS,
+    toolchains = [
+        "@buildifier_prebuilt//buildozer:toolchain",
+    ] + ([
+        "@bazel_tools//tools/test:default_test_toolchain_type",
+    ] if bazel_features.toolchains.has_default_test_toolchain_type else []),
     executable = True,
 )

deps.bzl

@@ -23,3 +23,11 @@ def buildifier_prebuilt_deps():
         strip_prefix = "rules_shell-0.6.1",
         url = "https://github.com/bazelbuild/rules_shell/releases/download/v0.6.1/rules_shell-v0.6.1.tar.gz",
     )
+
+    maybe(
+        http_archive,
+        name = "bazel_features",
+        sha256 = "adfdb3cffab3a99a63363d844d559a81965d2b61a6062dd51a3d2478d416768f",
+        strip_prefix = "bazel_features-1.45.0",
+        url = "https://github.com/bazel-contrib/bazel_features/releases/download/v1.45.0/bazel_features-v1.45.0.tar.gz",
+    )

examples/simple/WORKSPACE

@@ -9,6 +9,10 @@ load("@buildifier_prebuilt//:deps.bzl", "buildifier_prebuilt_deps")
 
 buildifier_prebuilt_deps()
 
+load("@bazel_features//:deps.bzl", "bazel_features_deps")
+
+bazel_features_deps()
+
 load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
 
 bazel_skylib_workspace()

examples/specify_assets/WORKSPACE

@@ -9,6 +9,10 @@ load("@buildifier_prebuilt//:deps.bzl", "buildifier_prebuilt_deps")
 
 buildifier_prebuilt_deps()
 
+load("@bazel_features//:deps.bzl", "bazel_features_deps")
+
+bazel_features_deps()
+
 load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
 
 bazel_skylib_workspace()

rules.bzl

@@ -2,6 +2,7 @@
 Rules to use the prebuilt buildifier / buildozer binaries
 """
 
+load("@bazel_features//:features.bzl", "bazel_features")
 load("@platforms//host:constraints.bzl", "HOST_CONSTRAINTS")
 load("//buildifier:buildifier_binary.bzl", _buildifier_binary = "buildifier_binary")
 load(
@@ -20,8 +21,12 @@ def _buildifier_impl(ctx):
 buildifier = rule(
     implementation = _buildifier_impl,
     attrs = buildifier_attr_factory(test_rule = False),
-    exec_compatible_with = HOST_CONSTRAINTS,
-    toolchains = ["@buildifier_prebuilt//buildifier:toolchain"],
+    exec_compatible_with = [] if bazel_features.toolchains.has_default_test_toolchain_type else HOST_CONSTRAINTS,
+    toolchains = [
+        "@buildifier_prebuilt//buildifier:toolchain",
+    ] + ([
+        "@bazel_tools//tools/test:default_test_toolchain_type",
+    ] if bazel_features.toolchains.has_default_test_toolchain_type else []),
     executable = True,
 )
 
@@ -32,7 +37,15 @@ _buildifier_test = rule(
     implementation = _buildifier_test_impl,
     attrs = buildifier_attr_factory(test_rule = True),
     exec_compatible_with = HOST_CONSTRAINTS,
-    toolchains = ["@buildifier_prebuilt//buildifier:toolchain"],
+    exec_groups = {
+        "test": exec_group(
+            toolchains = [
+                "@buildifier_prebuilt//buildifier:toolchain",
+            ] + ([
+                "@bazel_tools//tools/test:default_test_toolchain_type",
+            ] if bazel_features.toolchains.has_default_test_toolchain_type else []),
+        ),
+    },
     test = True,
 )