Fix --build_event_publish_all_actions with --remote_download_minimal

The ActionExecutedEvent references the primaryOutput of the executed
action (see ActionExecutedEvent::referencedLocalFiles).
ByteStreamBuildEventArtifactUploader::upload will try to ensure that
this referenced file is present on the remote cache.  It calls
file.isDirectory(), which will eventually go to
RemoteActionFileSystem::getRemoteInputMetadata.  However,
RemoteActionFileSystem::inputArtifactData only contains metadata about
the input files, not action outputs.

This change proposes a fix, where we make RemoteActionFileSystem
implement MetadataInjector, and inject information about output files
from ActionMetadataHandler::injectRemoteFile.

The implementation is likely not correct for all cases, but demonstrates
the issue and a possible approach to fix it.

src/main/java/com/google/devtools/build/lib/remote/RemoteActionFileSystem.java

@@ -16,9 +16,13 @@
 package com.google.devtools.build.lib.remote;
 
 import com.google.common.base.Preconditions;
+import com.google.devtools.build.lib.actions.ActionInput;
 import com.google.devtools.build.lib.actions.ActionInputMap;
+import com.google.devtools.build.lib.actions.Artifact;
+import com.google.devtools.build.lib.actions.Artifact.TreeFileArtifact;
 import com.google.devtools.build.lib.actions.FileArtifactValue;
 import com.google.devtools.build.lib.actions.FileArtifactValue.RemoteFileArtifactValue;
+import com.google.devtools.build.lib.actions.cache.MetadataInjector;
 import com.google.devtools.build.lib.vfs.DelegateFileSystem;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.FileStatus;
@@ -30,6 +34,9 @@
 import java.io.InputStream;
 import java.nio.channels.ReadableByteChannel;
 import java.util.Collection;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
 import javax.annotation.Nullable;
 
 /**
@@ -42,12 +49,13 @@
  *
  * <p>This implementation only supports creating local action outputs.
  */
-class RemoteActionFileSystem extends DelegateFileSystem {
+class RemoteActionFileSystem extends DelegateFileSystem implements MetadataInjector {
 
   private final Path execRoot;
   private final Path outputBase;
   private final ActionInputMap inputArtifactData;
   private final RemoteActionInputFetcher inputFetcher;
+  private final ConcurrentMap<String, RemoteFileArtifactValue> injectedMetadata = new ConcurrentHashMap<>();
 
   RemoteActionFileSystem(
       FileSystem localDelegate,
@@ -339,6 +347,10 @@ private RemoteFileArtifactValue getRemoteInputMetadata(String execPathString) {
     if (m != null && m.isRemote()) {
       return (RemoteFileArtifactValue) m;
     }
+    RemoteFileArtifactValue rm = injectedMetadata.get(execPathString);
+    if (rm != null) {
+      return rm;
+    }
     return null;
   }
 
@@ -383,4 +395,33 @@ protected Collection<Dirent> readdir(Path path, boolean followSymlinks) throws I
   protected void createHardLink(Path linkPath, Path originalPath) throws IOException {
     super.createHardLink(linkPath, originalPath);
   }
+
+  // MetadataInjector interface
+  @Override
+  public void addExpandedTreeOutput(TreeFileArtifact output) {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public void injectDigest(ActionInput output, FileStatus statNoFollow, byte[] digest) {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public void injectRemoteFile(Artifact output, byte[] digest, long size, int locationIndex) {
+    RemoteFileArtifactValue m = new FileArtifactValue.RemoteFileArtifactValue(digest, size, locationIndex);
+    Path transformedPath = getPath(output.getPath().getPathString());
+    injectedMetadata.put(execPathString(transformedPath), m);
+  }
+
+  @Override
+  public void injectRemoteDirectory(
+      Artifact.SpecialArtifact treeArtifact, Map<PathFragment, RemoteFileArtifactValue> children) {
+    throw new UnsupportedOperationException();
+  }
+
+  @Override
+  public void markOmitted(ActionInput output) {
+    throw new UnsupportedOperationException();
+  }
 }

src/main/java/com/google/devtools/build/lib/skyframe/ActionMetadataHandler.java

@@ -37,12 +37,14 @@
 import com.google.devtools.build.lib.actions.FilesetOutputSymlink;
 import com.google.devtools.build.lib.actions.cache.DigestUtils;
 import com.google.devtools.build.lib.actions.cache.MetadataHandler;
+import com.google.devtools.build.lib.actions.cache.MetadataInjector;
 import com.google.devtools.build.lib.util.io.TimestampGranularityMonitor;
 import com.google.devtools.build.lib.vfs.Dirent;
 import com.google.devtools.build.lib.vfs.Dirent.Type;
 import com.google.devtools.build.lib.vfs.FileStatus;
 import com.google.devtools.build.lib.vfs.FileStatusWithDigest;
 import com.google.devtools.build.lib.vfs.FileStatusWithDigestAdapter;
+import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import com.google.devtools.build.lib.vfs.RootedPath;
@@ -551,6 +553,13 @@ public void injectRemoteFile(Artifact output, byte[] digest, long size, int loca
     Preconditions.checkState(
         executionMode.get(), "Tried to inject %s outside of execution", output);
     store.injectRemoteFile(output, digest, size, locationIndex);
+
+    // Ensure that this artifact is also known to the remote filesystem that
+    // artifactPathResolver resolves to.
+    FileSystem fs = artifactPathResolver.toPath(output).getFileSystem();
+    if (fs instanceof MetadataInjector) {
+      ((MetadataInjector) fs).injectRemoteFile(output, digest, size, locationIndex);
+    }
   }
 
   @Override