Fix lcd arg parsing

src/main/python/ttconv/filters/doc/lcd.py

@@ -29,6 +29,7 @@
 import logging
 import typing
 from dataclasses import dataclass, field
+from numbers import Number
 
 from ttconv.config import ModuleConfiguration
 from ttconv.filters.document_filter import DocumentFilter
@@ -55,12 +56,21 @@ def _apply_bg_color(element: ContentElement, bg_color: ColorType):
  for child in element:
  _apply_bg_color(child, bg_color)
 
-def _safe_area_decoder(s):
+def _safe_area_decoder(s: Number) -> int:
  safe_area = int(s)
  if 30 < safe_area < 0:
  raise ValueError("Safe area must be an integer between 0 and 30")
  return safe_area
 
+def _color_decoder(s: typing.Optional[ColorType]) -> typing.Optional[ColorType]:
+ if s is None:
+ return None
+
+ if not isinstance(s, str):
+ raise ValueError("Color specification must be a string")
+
+ return ttconv.utils.parse_color(s)
+
 @dataclass
 class LCDDocFilterConfig(ModuleConfiguration):
  """Configuration class for the Least common denominator (LCD) filter"""
@@ -70,16 +80,16 @@ def name(cls):
  return "lcd"
 
  # specifies the safe area as an integer percentage
- safe_area: typing.Optional[int] = field(default=10, metadata={"decoder": int})
+ safe_area: typing.Optional[int] = field(default=10, metadata={"decoder": _safe_area_decoder})
 
  # preserve text alignment the text color
  preserve_text_align: typing.Optional[bool] = field(default=False, metadata={"decoder": bool})
 
  # overrides the text color
- color: typing.Optional[ColorType] = field(default=None, metadata={"decoder": ttconv.utils.parse_color})
+ color: typing.Optional[ColorType] = field(default=None, metadata={"decoder": _color_decoder})
 
  # overrides the background color
- bg_color: typing.Optional[ColorType] = field(default=None, metadata={"decoder": ttconv.utils.parse_color})
+ bg_color: typing.Optional[ColorType] = field(default=None, metadata={"decoder": _color_decoder})
 
 class LCDDocFilter(DocumentFilter):
  """Merges regions and removes all text formatting with the exception of color

src/test/python/test_config.py

@@ -125,6 +125,10 @@ def test_default_config_parsing(self):
  for exp_config in expected_configurations:
  self.assertTrue(exp_config in module_configurations)
 
+ def test_empty_config_parsing(self):
+
+ config_dict = json.loads('{}')
+
 
 if __name__ == '__main__':
  unittest.main()

src/test/python/test_tt.py

@@ -224,5 +224,12 @@ def test_lcd_filter(self):
  '--config', '{"lcd": {"bg_color": "blue", "safe_area": 0, "color": "red", "preserve_text_align": true}}'
  ])
 
+ tt.main(['convert',
+ '-i', in_path,
+ '-o', out_path,
+ '--filter', 'lcd',
+ '--config', '{"lcd": {"bg_color":"red"}}'
+ ])
+
 if __name__ == '__main__':
  unittest.main()