[DOCS] More verbose error when ffmpeg/ffprobe not found (#491)

src/ytdl_sub/config/config_validator.py

@@ -6,7 +6,8 @@ from mergedeep import mergedeep
 
 from ytdl_sub.prebuilt_presets import PREBUILT_PRESETS
 from ytdl_sub.utils.system import IS_WINDOWS
-from ytdl_sub.validators.file_path_validators import ExistingFileValidator
+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
 from ytdl_sub.validators.validators import LiteralDictValidator
 from ytdl_sub.validators.validators import StringValidator
@@ -41,10 +42,10 @@ class ConfigOptions(StrictDictValidator):
             key="lock_directory", validator=StringValidator, default=_DEFAULT_LOCK_DIRECTORY
         )
         self._ffmpeg_path = self._validate_key(
-            key="ffmpeg_path", validator=ExistingFileValidator, default=_DEFAULT_FFMPEG_PATH
+            key="ffmpeg_path", validator=FFmpegFileValidator, default=_DEFAULT_FFMPEG_PATH
         )
         self._ffprobe_path = self._validate_key(
-            key="ffprobe_path", validator=ExistingFileValidator, default=_DEFAULT_FFPROBE_PATH
+            key="ffprobe_path", validator=FFprobeFileValidator, default=_DEFAULT_FFPROBE_PATH
         )
 
     @property

src/ytdl_sub/validators/file_path_validators.py

@@ -8,14 +8,17 @@ from ytdl_sub.validators.string_formatter_validators import StringFormatterValid
 from ytdl_sub.validators.validators import StringValidator
 
 
-class ExistingFileValidator(StringValidator):
-    _expected_value_type_name = "file"
+class FFmpegFileValidator(StringValidator):
+    _expected_value_type_name = "ffmpeg dependency"
+    _ffmpeg_dependency = "ffmpeg"
 
     def __init__(self, name: str, value: Any):
         super().__init__(name, value)
-        if not os.path.isfile(self._value):
+        if not os.path.isfile(self.value):
             raise self._validation_exception(
-                f"Expects an existing file, but '{self.value}' is not a file"
+                f"Expects an {self._ffmpeg_dependency} executable at '{self.value}', but "
+                f"does not exist. See https://github.com/jmbannon/ytdl-sub#installation on how "
+                f"to install ffmpeg dependencies."
             )
 
     @property
@@ -24,6 +27,10 @@ class ExistingFileValidator(StringValidator):
         return str(Path(self._value))
 
 
+class FFprobeFileValidator(FFmpegFileValidator):
+    _ffmpeg_dependency = "ffprobe"
+
+
 class StringFormatterFilePathValidator(StringFormatterValidator):
     _expected_value_type_name = "filepath"
 

src/ytdl_sub/validators/validators.py

@@ -227,7 +227,7 @@ class DictValidator(Validator):
         if key not in self._dict and default is None:
             raise self._validation_exception(f"{key} is missing when it should be present.")
 
-        validator_name = f"{self._name}.{key}"
+        validator_name = f"{self._name}.{key}" if self._name else key
         validator_instance = validator(
             name=validator_name,
             value=self._dict.get(key, default),