From 280d3ad603b35b12f1cb8a25582fa4f0ccd63ef3 Mon Sep 17 00:00:00 2001
From: Googler <noreply@google.com>
Date: Tue, 25 Jun 2024 11:23:00 -0700
Subject: [PATCH] Allow creation of sentinel features in rule-based toolchains

BEGIN_PUBLIC
Makes the `args` attribute of `cc_feature` optional so that users may declare sentinel features that do not have any inherent arguments.
END_PUBLIC

PiperOrigin-RevId: 646545838
Change-Id: I470a496aec951608f21cc8ea693387c5b551c8a9
---
 cc/toolchains/feature.bzl                             | 1 -
 tests/rule_based_toolchain/features/BUILD             | 7 +++++++
 tests/rule_based_toolchain/features/features_test.bzl | 8 ++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/cc/toolchains/feature.bzl b/cc/toolchains/feature.bzl
index c81a756..312f184 100644
--- a/cc/toolchains/feature.bzl
+++ b/cc/toolchains/feature.bzl
@@ -125,7 +125,6 @@ Example:
             doc = """Whether or not this feature is enabled by default.""",
         ),
         "args": attr.label_list(
-            mandatory = True,
             doc = """Args that, when expanded, implement this feature.""",
             providers = [ArgsListInfo],
         ),
diff --git a/tests/rule_based_toolchain/features/BUILD b/tests/rule_based_toolchain/features/BUILD
index cc3c0c7..a8bfb54 100644
--- a/tests/rule_based_toolchain/features/BUILD
+++ b/tests/rule_based_toolchain/features/BUILD
@@ -109,6 +109,13 @@ util.helper_target(
     overrides = ":builtin_feature",
 )
 
+util.helper_target(
+    cc_feature,
+    name = "sentinel_feature",
+    enabled = True,
+    feature_name = "sentinel_feature_name",
+)
+
 analysis_test_suite(
     name = "test_suite",
     targets = TARGETS,
diff --git a/tests/rule_based_toolchain/features/features_test.bzl b/tests/rule_based_toolchain/features/features_test.bzl
index 2345cd7..ee18a07 100644
--- a/tests/rule_based_toolchain/features/features_test.bzl
+++ b/tests/rule_based_toolchain/features/features_test.bzl
@@ -37,6 +37,12 @@ visibility("private")
 
 _C_COMPILE_FILE = "tests/rule_based_toolchain/testdata/file1"
 
+def _sentinel_feature_test(env, targets):
+    sentinel_feature = env.expect.that_target(targets.sentinel_feature).provider(FeatureInfo)
+    sentinel_feature.name().equals("sentinel_feature_name")
+    sentinel_feature.args().args().contains_exactly([])
+    sentinel_feature.enabled().equals(True)
+
 def _simple_feature_test(env, targets):
     simple = env.expect.that_target(targets.simple).provider(FeatureInfo)
     simple.name().equals("feature_name")
@@ -154,6 +160,7 @@ TARGETS = [
     ":mutual_exclusion_feature",
     ":overrides",
     ":requires",
+    ":sentinel_feature",
     ":simple",
     ":simple2",
     ":transitive_constraint",
@@ -161,6 +168,7 @@ TARGETS = [
 
 # @unsorted-dict-items
 TESTS = {
+    "sentinel_feature_test": _sentinel_feature_test,
     "simple_feature_test": _simple_feature_test,
     "feature_collects_requirements_test": _feature_collects_requirements_test,
     "feature_collects_implies_test": _feature_collects_implies_test,