Dynamic configurations: have HostTransition just clone the

original options if they're already from the host.

This fixes an obscure incompatibility between Bazel's
flag invocation policy infrastructure and multiple host
configurations. In short, when multiple host configurations
are possible, policy settings may not get consistently
applied.

Bazel invocation policies: https://github.com/bazelbuild/bazel/blo[]d24e2b69789ea54762ab034fdafc205cdcecea5/src/main/protobuf/invocation_policy.proto

--
MOS_MIGRATED_REVID=122014371

1 files changed, 19 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/analysis/config/HostTransition.java b/src/main/java/com/google/devtools/build/lib/analysis/config/HostTransition.java
index 207b2f9915..2ea6a2fd2e 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/config/HostTransition.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/config/HostTransition.java
@@ -23,7 +23,25 @@ public final class HostTransition implements PatchTransition {
 
   @Override
   public BuildOptions apply(BuildOptions options) {
-    return options.createHostOptions(false);
+    if (options.get(BuildConfiguration.Options.class).isHost) {
+      // If the input already comes from the host configuration, just return the existing values.
+      //
+      // We don't do this just for convenience: if an
+      // {@link com.google.devtools.build.lib.runtime.proto.InvocationPolicyOuterClass.InvocationPolicy}
+      // overrides option defaults, {@link FragmentOptions#getHost} won't honor that policy. That's
+      // because it uses its own options parser that's not aware of the policy. This can create
+      // problems for, e.g., {@link JavaOptions#getHost}, which promotes --host_foo flags to
+      // --foo flags. That works the first time you do it (since both of the original values
+      // were policy-processed). But not subsequent times.
+      //
+      // There are various ways to solve this problem (pass the policy to host options computation,
+      // manually set host.hostFoo = original.hostFoo). But those raise larger questions about the
+      // nature of host/target relationships, so for the time being this is a straightforward
+      // and practical fix.
+      return options.clone();
+    } else {
+      return options.createHostOptions(false);
+    }
   }
 
   @Override