Fix AliasRule to skip platform and toolchain resolution.

This causes a cycle in loading when an alias of a platform or constraint is used.

Fixes https://github.com/bazelbuild/rules_go/issues/1161

Change-Id: I8b19ba94bfc52221416a3d99f5e5d4d80ce15bbd
PiperOrigin-RevId: 179853665

1 files changed, 9 insertions, 4 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/Alias.java b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
index ad4369a226..364f6744ea 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/Alias.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/Alias.java
@@ -63,11 +63,16 @@ public class Alias implements RuleConfiguredTargetFactory {
           <!-- #END_BLAZE_RULE.ATTRIBUTE -->*/
           .removeAttribute("licenses")
           .removeAttribute("distribs")
-          .add(attr("actual", LABEL)
-              .allowedFileTypes(FileTypeSet.ANY_FILE)
-              .allowedRuleClasses(ANY_RULE)
-              .mandatory())
+          .add(
+              attr("actual", LABEL)
+                  .allowedFileTypes(FileTypeSet.ANY_FILE)
+                  .allowedRuleClasses(ANY_RULE)
+                  .mandatory())
           .canHaveAnyProvider()
+          // Aliases themselves do not need toolchains or an execution platform, so this is fine.
+          // The actual target
+          // will resolve platforms and toolchains with no issues regardless of this setting.
+          .supportsPlatforms(false)
           .build();
     }