Make target_compatible_with work better on alias() targets

Currently the `target_compatible_with` on `alias()` targets only works
when a `select()` is involved. That's because `alias()` targets by
default don't have a toolchains evaluated.

This patch changes the behaviour by making it so all `alias()` targets
with a `target_compatible_with` attribute are skipped appropriately.
When `target_compatible_with` is present, then toolchains are
evaluated for `alias()` targets.

The implementation is basically an enhancement to @gregestren's
1c3a245 (bazelbuild#14310). In
addition to resolving toolchains when a `select()` is present, Bazel
will now also resolve toolchains when a `target_compatible_with`
attribute is set.

src/main/java/com/google/devtools/build/lib/packages/Rule.java

@@ -1195,8 +1195,10 @@ public boolean useToolchainResolution() {
  return true;
  } else if (mode == ToolchainResolutionMode.HAS_SELECT) {
  RawAttributeMapper attr = RawAttributeMapper.of(this);
- return (attr.has(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE)
- && !attr.get(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE, BuildType.LABEL_LIST).isEmpty());
+ return ((attr.has(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE)
+ && !attr.get(RuleClass.CONFIG_SETTING_DEPS_ATTRIBUTE, BuildType.LABEL_LIST).isEmpty()) ||
+ (attr.has(RuleClass.TARGET_COMPATIBLE_WITH_ATTR)
+ && !attr.get(RuleClass.TARGET_COMPATIBLE_WITH_ATTR, BuildType.LABEL_LIST).isEmpty()));
  } else {
  return false;
  }

src/test/shell/integration/target_compatible_with_test.sh

@@ -1584,4 +1584,38 @@ EOF
  expect_not_log "${debug_message5}"
 }
 
+# Validate what happens when setting `target_compatible_with` directly on an
+# alias(). This is a regression test for
+# https:/bazelbuild/bazel/issues/17663.
+function test_alias_incompatibility() {
+ cat >> target_skipping/BUILD <<'EOF'
+filegroup(
+ name = "test_cc_filegroup",
+ srcs = ["test.cc"],
+)
+
+alias(
+ name = "test_cc_filegroup_alias",
+ actual = ":test_cc_filegroup",
+ target_compatible_with = [":foo3"],
+)
+
+cc_library(
+ name = "test_cc",
+ srcs = [":test_cc_filegroup_alias"],
+)
+EOF
+
+ echo > target_skipping/test.cc
+
+ cd target_skipping || fail "couldn't cd into workspace"
+ bazel build \
+ --show_result=10 \
+ --host_platform=@//target_skipping:foo1_bar1_platform \
+ --platforms=@//target_skipping:foo1_bar1_platform \
+ //target_skipping:test_cc &> "${TEST_log}" \
+ && fail "Bazel passed unexpectedly"
+ expect_log_once 'ERROR: Target //target_skipping:test_cc is incompatible and cannot be built, but was explicitly requested.'
+}
+
 run_suite "target_compatible_with tests"