diff: account for deleted workspace data (iterative#5205)

* diff: add test for deleted data in addition to .dvc file

* diff: handle deleted data when checking for missing cache

dvc/repo/diff.py

@@ -148,11 +148,14 @@ def _dir_output_paths(repo_tree, output, targets=None):
 def _filter_missing(repo, paths):
     repo_tree = RepoTree(repo, stream=True)
     for path in paths:
-        metadata = repo_tree.metadata(path)
-        if metadata.is_dvc:
-            out = metadata.outs[0]
-            if out.status().get(str(out)) == "not in cache":
-                yield path
+        try:
+            metadata = repo_tree.metadata(path)
+            if metadata.is_dvc:
+                out = metadata.outs[0]
+                if out.status().get(str(out)) == "not in cache":
+                    yield path
+        except FileNotFoundError:
+            pass
 
 
 def _targets_to_path_infos(repo, targets):

tests/func/test_diff.py

@@ -60,9 +60,12 @@ def test_no_cache_entry(tmp_dir, scm, dvc):
     }
 
 
-def test_deleted(tmp_dir, scm, dvc):
+@pytest.mark.parametrize("delete_data", [True, False])
+def test_deleted(tmp_dir, scm, dvc, delete_data):
     tmp_dir.dvc_gen("file", "text", commit="add file")
     (tmp_dir / "file.dvc").unlink()
+    if delete_data:
+        (tmp_dir / "file").unlink()
 
     assert dvc.diff() == {
         "added": [],