Fix KeyError: 'value' for parsing TMX Map Format

[laqieer]

Problem

KeyError: 'value' when parsing .tmx files.

Tiled version: 1.9.0
pytiled_parser version: 2.1.0

Traceback (most recent call last):
  File "./make_map.py", line 11, in <module>
    map = pytiled_parser.parse_map(map_file)
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parser.py", line 25, in parse_map
    return tmx_map_parse(file)  # type: ignore
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/tiled_map.py", line 65, in parse
    layers.append(parse_layer(element, parent_dir))
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/layer.py", line 365, in parse
    return _parse_object_layer(raw_layer, parent_dir)
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/layer.py", line 270, in _parse_object_layer
    objects.append(parse_object(object_, parent_dir))
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/tiled_object.py", line 294, in parse
    return _parse_tile(raw_object, new_tileset, new_tileset_path)
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/tiled_object.py", line 156, in _parse_tile
    **_parse_common(raw_object).__dict__
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/tiled_object.py", line 60, in _parse_common
    common.properties = parse_properties(properties_element)
  File "/Users/laqieer/Library/Python/3.8/lib/python/site-packages/pytiled_parser/parsers/tmx/properties.py", line 18, in parse
    value_ = raw_property.attrib["value"]
KeyError: 'value'

Reason

According to Tiled's doc:

Class properties will have their member values stored in a nested <properties> element.

In this case, raw_property.attrib doesn't have key value:

{'name': 'unit', 'type': 'class', 'propertytype': 'Unit'}

Solution

This PR use get() to get the value of key value instead. It avoids the crash when opening the TMX file with parse_map, but it cannot get the actual value of Class property. Class property's support for TMX is introduced in #56 and reverted in 9e8e3b9. In contrast, this PR is to fix the possible KeyError here rather than support Class properties.

[Cleptomania]

Hey thanks for this, I'll merge it in and push out a release for it today.

I do intend to add proper support for classes at some point, but it needs more thought given to it and how exactly we want it to work.