Report nonexistent directories from IsDirectoryEmpty

#1762 (comment)

Bug: b/457549895

Author: Databean

base/cvd/cuttlefish/common/libs/utils/files.cpp

@@ -284,20 +284,14 @@ bool CanAccess(const std::string& path, const int mode) {
   return access(path.c_str(), mode) == 0;
 }
 
-bool IsDirectoryEmpty(const std::string& path) {
+Result<bool> IsDirectoryEmpty(const std::string& path) {
   std::unique_ptr<DIR, int (*)(DIR*)> direc(opendir(path.c_str()), closedir);
-  if (!direc) {
-    LOG(ERROR) << "IsDirectoryEmpty test failed with " << path
-               << " as it failed to be open" << std::endl;
-    return false;
-  }
+  CF_EXPECTF(direc.get(), "opendir('{}') failed: {}", path, StrError(errno));
 
-  int cnt {0};
+  int cnt = 0;
   while (::readdir(direc.get())) {
     cnt++;
     if (cnt > 2) {
-    LOG(ERROR) << "IsDirectoryEmpty test failed with " << path
-               << " as it exists but not empty" << std::endl;
       return false;
     }
   }

base/cvd/cuttlefish/common/libs/utils/files.h

@@ -62,7 +62,7 @@ Result<void> EnsureDirectoryExists(const std::string& directory_path,
 Result<void> ChangeGroup(const std::string& path,
                          const std::string& group_name);
 bool CanAccess(const std::string& path, int mode);
-bool IsDirectoryEmpty(const std::string& path);
+Result<bool> IsDirectoryEmpty(const std::string& path);
 Result<void> RecursivelyRemoveDirectory(const std::string& path);
 bool Copy(const std::string& from, const std::string& to);
 off_t FileSize(const std::string& path);

base/cvd/cuttlefish/common/libs/utils/files_test.cpp

@@ -92,7 +92,7 @@ TEST_F(FilesTests, MoveDirectoryContentsFailsIfSourceIsNotADirectory) {
 TEST_F(FilesTests, MoveDirectoryContents) {
   Result<void> result = MoveDirectoryContents(src_dir_, dst_dir_);
   EXPECT_THAT(result, IsOk());
-  EXPECT_THAT(IsDirectoryEmpty(src_dir_), IsTrue());
+  EXPECT_THAT(IsDirectoryEmpty(src_dir_), IsOkAndValue(true));
   EXPECT_THAT(FileExists(dst_dir_ + "/file1.txt"), IsTrue());
   EXPECT_THAT(FileExists(dst_dir_ + "/sub_dir/file2.txt"), IsTrue());
 }

base/cvd/cuttlefish/host/commands/assemble_cvd/assemble_cvd.cc

@@ -453,7 +453,7 @@ Result<const CuttlefishConfig*> InitFilesystemAndCreateConfig(
       std::string vsock_dir = fmt::format("{}/vsock_{}_{}", TempDir(),
                                           instance.vsock_guest_cid(), getuid());
       if (DirectoryExists(vsock_dir, /* follow_symlinks */ false) &&
-          !IsDirectoryEmpty(vsock_dir)) {
+          !CF_EXPECT(IsDirectoryEmpty(vsock_dir))) {
         CF_EXPECT(RecursivelyRemoveDirectory(vsock_dir));
       }
       CF_EXPECT(EnsureDirectoryExists(vsock_dir, default_mode, default_group));

base/cvd/cuttlefish/host/commands/assemble_cvd/flags.cc

@@ -1359,7 +1359,8 @@ Result<void> SetDefaultFlagsForCrosvm(
   bool default_enable_sandbox =
       supported_archs.find(HostArch()) != supported_archs.end() &&
       EnsureDirectoryExists(kCrosvmVarEmptyDir).ok() &&
-      IsDirectoryEmpty(kCrosvmVarEmptyDir) && !IsRunningInContainer();
+      CF_EXPECT(IsDirectoryEmpty(kCrosvmVarEmptyDir)) &&
+      !IsRunningInContainer();
 
   std::string default_enable_sandbox_str = "";
   for (int instance_index = 0; instance_index < instance_nums.size();