raise in download_to if not exists (#433)

Author: pjbull

HISTORY.md

@@ -7,6 +7,7 @@
 - Drop support for Python 3.7; pin minimal `boto3` version to Python 3.8+ versions. (PR [#407](https://github.com/drivendataorg/cloudpathlib/pull/407))
 - fix: use native `exists()` method in `GSClient`. (PR [#420](https://github.com/drivendataorg/cloudpathlib/pull/420))
 - Enhancement: lazy instantiation of default client (PR [#432](https://github.com/drivendataorg/cloudpathlib/issues/432), Issue [#428](https://github.com/drivendataorg/cloudpathlib/issues/428))
+- Adds existence check before downloading in `download_to` (Issue [#430](https://github.com/drivendataorg/cloudpathlib/issues/430), PR [#432](https://github.com/drivendataorg/cloudpathlib/pull/432))
 
 ## v0.18.1 (2024-02-26)
 

cloudpathlib/cloudpath.py

@@ -63,6 +63,7 @@ def _make_selector(pattern_parts, _flavour, case_sensitive=True):
     CloudPathFileExistsError,
     CloudPathIsADirectoryError,
     CloudPathNotADirectoryError,
+    CloudPathNotExistsError,
     CloudPathNotImplementedError,
     DirectoryNotEmptyError,
     IncompleteImplementationError,
@@ -899,6 +900,10 @@ def stat(self, follow_symlinks: bool = True) -> os.stat_result:
     # ===========  public cloud methods, not in pathlib ===============
     def download_to(self, destination: Union[str, os.PathLike]) -> Path:
         destination = Path(destination)
+
+        if not self.exists():
+            raise CloudPathNotExistsError(f"Cannot download because path does not exist: {self}")
+
         if self.is_file():
             if destination.is_dir():
                 destination = destination / self.name

cloudpathlib/exceptions.py

@@ -20,6 +20,10 @@ class CloudPathFileExistsError(CloudPathException, FileExistsError):
     pass
 
 
+class CloudPathNotExistsError(CloudPathException):
+    pass
+
+
 class CloudPathIsADirectoryError(CloudPathException, IsADirectoryError):
     pass
 

tests/test_cloudpath_file_io.py

@@ -10,6 +10,7 @@
 from cloudpathlib import CloudPath
 
 from cloudpathlib.exceptions import (
+    CloudPathNotExistsError,
     CloudPathIsADirectoryError,
     CloudPathNotImplementedError,
     DirectoryNotEmptyError,
@@ -396,6 +397,9 @@ def test_file_read_writes(rig, tmp_path):
     )
     assert cloud_rel_paths == dled_rel_paths
 
+    with pytest.raises(CloudPathNotExistsError):
+        (p / "not_exists_file").download_to(dl_file)
+
 
 def test_dispatch_to_local_cache(rig):
     p = rig.create_cloud_path("dir_0/file0_1.txt")