dvc ls: not raise PathMissingError on empty dir.

fix #5841

dvc/repo/ls.py

@@ -31,11 +31,11 @@ def ls(url, path=None, rev=None, recursive=None, dvc_only=False):
     with Repo.open(url, rev=rev, subrepos=True, uninitialized=True) as repo:
         path = path or ""
 
-        ret = _ls(repo.repo_fs, path, recursive, dvc_only)
-
-        if path and not ret:
+        if path and not repo.repo_fs.exists(path):
             raise PathMissingError(path, repo, dvc_only=dvc_only)
 
+        ret = _ls(repo.repo_fs, path, recursive, dvc_only)
+
         ret_list = []
         for path, info in ret.items():
             info["path"] = path

tests/func/test_ls.py

@@ -150,9 +150,20 @@ def test_ls_repo_with_path_dir_dvc_only_empty(tmp_dir, dvc, scm):
     tmp_dir.scm_gen(FS_STRUCTURE, commit="init")
     tmp_dir.dvc_gen(DVC_STRUCTURE, commit="dvc")
     tmp_dir.scm_gen({"folder/.keep": "content"}, commit="add .keep")
+    tmp_dir.scm_gen({"empty_scm_folder/": {}}, commit="add scm empty")
+    tmp_dir.dvc_gen({"empty_dvc_folder": {}}, commit="empty dvc folder")
 
     with pytest.raises(PathMissingError):
-        Repo.ls(os.fspath(tmp_dir), path="folder", dvc_only=True)
+        Repo.ls(os.fspath(tmp_dir), path="not_exist_folder")
+
+    assert Repo.ls(os.fspath(tmp_dir), path="empty_scm_folder") == []
+
+    assert Repo.ls(os.fspath(tmp_dir), path="folder", dvc_only=True) == []
+
+    assert (
+        Repo.ls(os.fspath(tmp_dir), path="empty_dvc_folder", dvc_only=True)
+        == []
+    )
 
 
 def test_ls_repo_with_path_subdir(tmp_dir, dvc, scm):