Fixup 12494: Address copilot comments

Author: sauravzg

xds/src/main/java/io/grpc/xds/internal/headermutations/HeaderMutationFilter.java

@@ -47,10 +47,10 @@ public HeaderMutationFilter(Optional<HeaderMutationRulesConfig> mutationRules) {
   public HeaderMutations filter(HeaderMutations mutations)
       throws HeaderMutationDisallowedException {
     ImmutableList<HeaderValueOption> allowedHeaders =
-        filterCollection(mutations.headers(), this::shouldIgnore, this::isHeaderMutationAllowed);
+        filterCollection(mutations.headers(), this::isDisallowed, this::isHeaderMutationAllowed);
     ImmutableList<String> allowedHeadersToRemove =
-        filterCollection(mutations.headersToRemove(), this::shouldIgnore,
-            this::isHeaderMutationAllowed);
+        filterCollection(mutations.headersToRemove(), this::isDisallowed,
+                this::isHeaderMutationAllowed);
     return HeaderMutations.create(allowedHeaders, allowedHeadersToRemove);
   }
 
@@ -68,19 +68,18 @@ private <T> ImmutableList<T> filterCollection(Collection<T> items,
       if (isAllowedPredicate.test(item)) {
         allowed.add(item);
       } else if (disallowIsError()) {
-        throw new HeaderMutationDisallowedException(
-            "Header mutation disallowed for header: " + item);
+        throw new HeaderMutationDisallowedException("Header mutation disallowed");
       }
     }
     return allowed.build();
   }
 
-  private boolean shouldIgnore(String key) {
-    return HeaderValueValidationUtils.shouldIgnore(key);
+  private boolean isDisallowed(String key) {
+    return HeaderValueValidationUtils.isDisallowed(key);
   }
 
-  private boolean shouldIgnore(HeaderValueOption option) {
-    return HeaderValueValidationUtils.shouldIgnore(option.header());
+  private boolean isDisallowed(HeaderValueOption option) {
+    return HeaderValueValidationUtils.isDisallowed(option.header());
   }
 
   private boolean isHeaderMutationAllowed(HeaderValueOption option) {

xds/src/main/java/io/grpc/xds/internal/headermutations/HeaderMutator.java

@@ -50,7 +50,10 @@ public void applyMutations(final HeaderMutations mutations, Metadata headers) {
     // in case of conflicts. Copying the order from Envoy here, which does removals at the end.
     applyHeaderUpdates(mutations.headers(), headers);
     for (String headerToRemove : mutations.headersToRemove()) {
-      headers.discardAll(Metadata.Key.of(headerToRemove, Metadata.ASCII_STRING_MARSHALLER));
+      Metadata.Key<?> key = headerToRemove.endsWith(Metadata.BINARY_HEADER_SUFFIX)
+          ? Metadata.Key.of(headerToRemove, Metadata.BINARY_BYTE_MARSHALLER)
+          : Metadata.Key.of(headerToRemove, Metadata.ASCII_STRING_MARSHALLER);
+      headers.discardAll(key);
     }
   }
 
@@ -67,11 +70,19 @@ private void updateHeader(final HeaderValueOption option, Metadata mutableHeader
     boolean keepEmptyValue = option.keepEmptyValue();
 
     if (header.key().endsWith(Metadata.BINARY_HEADER_SUFFIX)) {
-      updateHeader(action, Metadata.Key.of(header.key(), Metadata.BINARY_BYTE_MARSHALLER),
-          header.rawValue().get().toByteArray(), mutableHeaders, keepEmptyValue);
+      if (header.rawValue().isPresent()) {
+        updateHeader(action, Metadata.Key.of(header.key(), Metadata.BINARY_BYTE_MARSHALLER),
+            header.rawValue().get().toByteArray(), mutableHeaders, keepEmptyValue);
+      } else {
+        logger.fine("Missing binary rawValue for header: " + header.key());
+      }
     } else {
-      updateHeader(action, Metadata.Key.of(header.key(), Metadata.ASCII_STRING_MARSHALLER),
-          header.value().get(), mutableHeaders, keepEmptyValue);
+      if (header.value().isPresent()) {
+        updateHeader(action, Metadata.Key.of(header.key(), Metadata.ASCII_STRING_MARSHALLER),
+            header.value().get(), mutableHeaders, keepEmptyValue);
+      } else {
+        logger.fine("Missing value for header: " + header.key());
+      }
     }
   }