pull: skip isdir() checks on downloading files (#5696)

* pull: use download_file

* tree: implement filesystem.download_file

dvc/fs/base.py

@@ -1,6 +1,6 @@
 import logging
 from concurrent.futures import ThreadPoolExecutor, as_completed
-from functools import partial
+from functools import partial, partialmethod
 from multiprocessing import cpu_count
 from typing import Any, ClassVar, Dict, FrozenSet, Optional
 
@@ -258,6 +258,7 @@ class BaseFileSystem:
         name=None,
         no_progress_bar=False,
         jobs=None,
+        _only_file=False,
         **kwargs,
     ):
         if not hasattr(self, "_download"):
@@ -273,12 +274,14 @@ class BaseFileSystem:
         if to_info.scheme != "local":
             raise NotImplementedError
 
-        if self.isdir(from_info):
+        if not _only_file and self.isdir(from_info):
             return self._download_dir(
                 from_info, to_info, name, no_progress_bar, jobs, **kwargs,
             )
         return self._download_file(from_info, to_info, name, no_progress_bar,)
 
+    download_file = partialmethod(download, _only_file=True)
+
     def _download_dir(
         self, from_info, to_info, name, no_progress_bar, jobs, **kwargs,
     ):

dvc/remote/base.py

@@ -309,7 +309,7 @@ class Remote:
         )
 
         if download:
-            func = _log_exceptions(self.fs.download, "download")
+            func = _log_exceptions(self.fs.download_file, "download")
             status = STATUS_DELETED
             desc = "Downloading"
         else:

tests/func/test_external_repo.py

@@ -52,7 +52,7 @@ def test_cache_reused(erepo_dir, mocker, local_cloud):
         erepo_dir.dvc_gen("file", "text", commit="add file")
     erepo_dir.dvc.push()
 
-    download_spy = mocker.spy(LocalFileSystem, "download")
+    download_spy = mocker.spy(LocalFileSystem, "download_file")
 
     # Use URL to prevent any fishy optimizations
     url = f"file://{erepo_dir}"