add: handle long filenames (#5201)

dvc/tree/local.py

@@ -174,7 +174,7 @@ class LocalTree(BaseTree):
         move(from_info, to_info, mode=mode)
 
     def copy(self, from_info, to_info):
-        tmp_info = to_info.parent / tmp_fname(to_info.name)
+        tmp_info = to_info.parent / tmp_fname("")
         try:
             System.copy(from_info, tmp_info)
             os.chmod(tmp_info, self.file_mode)
@@ -185,7 +185,7 @@ class LocalTree(BaseTree):
 
     def copy_fobj(self, fobj, to_info):
         self.makedirs(to_info.parent)
-        tmp_info = to_info.parent / tmp_fname(to_info.name)
+        tmp_info = to_info.parent / tmp_fname("")
         try:
             copy_fobj_to_file(fobj, tmp_info)
             os.chmod(tmp_info, self.file_mode)
@@ -229,7 +229,7 @@ class LocalTree(BaseTree):
         return System.is_hardlink(path_info)
 
     def reflink(self, from_info, to_info):
-        tmp_info = to_info.parent / tmp_fname(to_info.name)
+        tmp_info = to_info.parent / tmp_fname("")
         System.reflink(from_info, tmp_info)
         # NOTE: reflink has its own separate inode, so you can set permissions
         # that are different from the source.

tests/func/test_add.py

@@ -1,3 +1,4 @@
+import errno
 import filecmp
 import logging
 import os
@@ -972,3 +973,21 @@ def test_add_preserve_meta(tmp_dir, dvc):
         meta: some metadata
     """
     )
+
+
+# NOTE: unless long paths are enabled on Windows, PATH_MAX and NAME_MAX
+# are the same 260 chars, which makes the test unnecessarily complex
+@pytest.mark.skipif(os.name == "nt", reason="unsupported on Windows")
+def test_add_long_fname(tmp_dir, dvc):
+    name_max = os.pathconf(tmp_dir, "PC_NAME_MAX")
+    name = "a" * name_max
+    tmp_dir.gen({"data": {name: "foo"}})
+
+    # nothing we can do in this case, as the resulting dvcfile
+    # will definitely exceed NAME_MAX
+    with pytest.raises(OSError) as info:
+        dvc.add(os.path.join("data", name))
+    assert info.value.errno == errno.ENAMETOOLONG
+
+    dvc.add("data")
+    assert (tmp_dir / "data").read_text() == {name: "foo"}