Fix an issue with cached EventHandlers in SkyQueryEnvironment's resolver

Because the event handler's inner handlers are removed after each query
command, caching the handler caused a subset of subsequent commands'
errors (those reported through the resolver's handler) to go unlogged.

Also fix a bug with cycle detection in DelegatingWalkableGraph.

--
PiperOrigin-RevId: 145124271
MOS_MIGRATED_REVID=145124271

src/main/java/com/google/devtools/build/lib/query2/SkyQueryEnvironment.java

@@ -207,7 +207,6 @@ protected SkyQueryEnvironment(
   }
 
   private void beforeEvaluateQuery() throws InterruptedException {
-    boolean resolverNeedsRecreation = false;
     if (graph == null || !graphFactory.isUpToDate(universeKey)) {
       // If this environment is uninitialized or the graph factory needs to evaluate, do so. We
       // assume here that this environment cannot be initialized-but-stale if the factory is up
@@ -224,21 +223,17 @@ private void beforeEvaluateQuery() throws InterruptedException {
 
       graphBackedRecursivePackageProvider =
           new GraphBackedRecursivePackageProvider(graph, universeTargetPatternKeys, pkgPath);
-      resolverNeedsRecreation = true;
     }
     if (forkJoinPool == null) {
       forkJoinPool =
           NamedForkJoinPool.newNamedPool("QueryEnvironment", queryEvaluationParallelismLevel);
-      resolverNeedsRecreation = true;
-    }
-    if (resolverNeedsRecreation) {
-      resolver =
-          new RecursivePackageProviderBackedTargetPatternResolver(
-              graphBackedRecursivePackageProvider,
-              eventHandler,
-              TargetPatternEvaluator.DEFAULT_FILTERING_POLICY,
-              packageSemaphore);
     }
+    resolver =
+        new RecursivePackageProviderBackedTargetPatternResolver(
+            graphBackedRecursivePackageProvider,
+            eventHandler,
+            TargetPatternEvaluator.DEFAULT_FILTERING_POLICY,
+            packageSemaphore);
   }
 
   protected MultisetSemaphore<PackageIdentifier> makeFreshPackageMultisetSemaphore() {

src/main/java/com/google/devtools/build/skyframe/DelegatingWalkableGraph.java

@@ -14,6 +14,7 @@
 package com.google.devtools.build.skyframe;
 
 import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import com.google.devtools.build.lib.util.Preconditions;
 import com.google.devtools.build.skyframe.QueryableGraph.Reason;
@@ -92,7 +93,7 @@ public boolean isCycle(SkyKey key) throws InterruptedException {
       return false;
     }
     ErrorInfo errorInfo = entry.getErrorInfo();
-    return errorInfo != null && errorInfo.getCycleInfo() != null;
+    return errorInfo != null && !Iterables.isEmpty(errorInfo.getCycleInfo());
   }
 
   @Nullable