index: build_data_index: handle empty dirs (#8959)

Fixes https://github.com/iterative/dvc/issues/8958

dvc/repo/index.py

@@ -526,9 +526,9 @@ def build_data_index(
             out_entry = DataIndexEntry(path=out_path, fs=fs)
 
         out_entry.key = key
+        data.add(out_entry)
 
         if not out_entry.meta or not out_entry.meta.isdir:
-            data.add(out_entry)
             continue
 
         for entry in build_entries(
@@ -546,8 +546,7 @@ def build_data_index(
             tree_meta, tree = build_tree(data, key)
             out_entry.meta = tree_meta
             out_entry.hash_info = tree.hash_info
-
-        out_entry.loaded = True
-        data.add(out_entry)
+            out_entry.loaded = True
+            data.add(out_entry)
 
     return data

tests/func/test_data_status.py

@@ -442,3 +442,18 @@ def test_root_from_file_to_dir(M, tmp_dir, dvc, scm):
         },
         "git": M.dict(),
     }
+
+
+def test_empty_dir(tmp_dir, scm, dvc, M):
+    # regression testing for https://github.com/iterative/dvc/issues/8958
+    tmp_dir.dvc_gen({"data": {"foo": "foo"}})
+    remove("data")
+
+    (tmp_dir / "data").mkdir()
+
+    assert dvc.data_status() == {
+        **EMPTY_STATUS,
+        "committed": {"added": [join("data", "")]},
+        "uncommitted": {"modified": [join("data", "")]},
+        "git": M.dict(),
+    }