[BACKEND] Validate write permissions on working directory and output directory

src/ytdl_sub/config/config_validator.py

@@ -12,6 +12,8 @@ from ytdl_sub.config.defaults import DEFAULT_FFPROBE_PATH
 from ytdl_sub.config.defaults import DEFAULT_LOCK_DIRECTORY
 from ytdl_sub.config.defaults import MAX_FILE_NAME_BYTES
 from ytdl_sub.prebuilt_presets import PREBUILT_PRESETS
+from ytdl_sub.utils.exceptions import SubscriptionPermissionError
+from ytdl_sub.utils.file_handler import FileHandler
 from ytdl_sub.validators.file_path_validators import FFmpegFileValidator
 from ytdl_sub.validators.file_path_validators import FFprobeFileValidator
 from ytdl_sub.validators.strict_dict_validator import StrictDictValidator
@@ -147,6 +149,12 @@ class ConfigOptions(StrictDictValidator):
             key="file_name_max_bytes", validator=IntValidator, default=MAX_FILE_NAME_BYTES
         )
 
+        if not FileHandler.is_path_writable(self.working_directory):
+            raise SubscriptionPermissionError(
+                "ytdl-sub does not have permissions to the working directory: "
+                f"{self.working_directory}"
+            )
+
     @property
     def working_directory(self) -> str:
         """

src/ytdl_sub/subscriptions/base_subscription.py

@@ -10,6 +10,8 @@ from ytdl_sub.config.preset_options import OutputOptions
 from ytdl_sub.config.preset_options import YTDLOptions
 from ytdl_sub.downloaders.url.validators import MultiUrlValidator
 from ytdl_sub.entries.variables.override_variables import SubscriptionVariables
+from ytdl_sub.utils.exceptions import SubscriptionPermissionError
+from ytdl_sub.utils.file_handler import FileHandler
 from ytdl_sub.utils.file_handler import FileHandlerTransactionLog
 from ytdl_sub.utils.logger import Logger
 from ytdl_sub.ytdl_additions.enhanced_download_archive import EnhancedDownloadArchive
@@ -94,6 +96,12 @@ class BaseSubscription(ABC):
 
         self._exception: Optional[Exception] = None
 
+        if not FileHandler.is_path_writable(self.output_directory):
+            raise SubscriptionPermissionError(
+                "ytdl-sub does not have write permissions to the output directory: "
+                f"{self.output_directory}"
+            )
+
     @property
     def download_archive(self) -> EnhancedDownloadArchive:
         """

src/ytdl_sub/utils/exceptions.py

@@ -40,3 +40,7 @@ class FileNotDownloadedException(ValueError):
 
 class ExperimentalFeatureNotEnabled(ValidationException):
     """Feature is not enabled for usage"""
+
+
+class SubscriptionPermissionError(ValidationException):
+    """Early-caught permission error"""

src/ytdl_sub/utils/file_handler.py

@@ -379,6 +379,22 @@ class FileHandler:
         """
         return self._file_handler_transaction_log
 
+    @classmethod
+    def is_path_writable(cls, src_file_path: Union[str, Path]) -> bool:
+        """"
+        Check whether a path is writable. If it does not exist, try to find the base directory
+        and check permissions on that.
+        """
+        path = os.path.abspath(src_file_path)
+
+        while not os.path.exists(path):
+            new_path = os.path.dirname(path)
+            if new_path == path:  # reached root
+                break
+            path = new_path
+
+        return os.access(path, os.W_OK)
+
     @classmethod
     def copy(cls, src_file_path: Union[str, Path], dst_file_path: Union[str, Path]):
         """

tests/unit/utils/test_file_handler.py

@@ -0,0 +1,20 @@
+import pytest
+
+from ytdl_sub.utils.file_handler import FileHandler
+from ytdl_sub.utils.system import IS_WINDOWS
+
+
+class TestFileHandler:
+
+    def test_directory_exists(self):
+        if IS_WINDOWS:
+            return
+
+        assert FileHandler.is_path_writable("/tmp")
+        assert FileHandler.is_path_writable("/tmp/")
+        assert FileHandler.is_path_writable("/tmp/non-existent")
+        assert FileHandler.is_path_writable("/tmp/non-existent/")
+        assert FileHandler.is_path_writable("/tmp/non-existent/nested")
+
+        assert not FileHandler.is_path_writable("/lol-in-root")
+        assert not FileHandler.is_path_writable("/")