GL style parse failure

[tomchadwin]

Might be specific to QGIS3 (EDIT: no, same error with QGIS2).

I'm getting this error when trying to use a published GL style for OS ZoomStack.

Path: C:/Users/tchadwin/Desktop/OS-Open-Zoomstack.mbtiles (downloaded from https://www.ordnancesurvey.co.uk/business-and-government/products/os-open-zoomstack.html)

GL Style JSON URL: https://raw.githubusercontent.com/OrdnanceSurvey/OS-Open-Zoomstack-Stylesheets/master/Vector%20Tiles/Mapbox%20GL%20Styles/OS%20Outdoor.json

[2018-07-23 10:10:25,545] [MainThread  ] [ERROR   ]  Style generation failed: (<class 'AttributeError'>, AttributeError("'list' object has no attribute 'startswith'",), <traceback object at 0x000000000E4A0948>), Traceback (most recent call last):
  File "C:/Users/tchadwin/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\vector_tiles_reader\vtr_plugin.py", line 421, in _create_styles
    core.generate_styles(data, output_directory, web_request_executor=self._load_style_data)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 50, in generate_styles
    styles = process(style_json)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 111, in process
    qgis_styles = get_styles(l)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 299, in get_styles
    all_values.extend(get_properties_by_zoom(layer, "paint/fill-color", is_color=True, default="rgba(0,0,0,0)"))
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 527, in get_properties_by_zoom
    value = parse_color(value)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 424, in parse_color
    if color.startswith("#"):
AttributeError: 'list' object has no attribute 'startswith'
Traceback (most recent call last):
  File "C:/Users/tchadwin/AppData/Roaming/QGIS/QGIS3\profiles\default/python/plugins\vector_tiles_reader\vtr_plugin.py", line 421, in _create_styles
    core.generate_styles(data, output_directory, web_request_executor=self._load_style_data)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 50, in generate_styles
    styles = process(style_json)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 111, in process
    qgis_styles = get_styles(l)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 299, in get_styles
    all_values.extend(get_properties_by_zoom(layer, "paint/fill-color", is_color=True, default="rgba(0,0,0,0)"))
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 527, in get_properties_by_zoom
    value = parse_color(value)
  File "C:\Users\tchadwin\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\vector_tiles_reader\ext-libs\mapboxstyle2qgis\core\__init__.py", line 424, in parse_color
    if color.startswith("#"):
AttributeError: 'list' object has no attribute 'startswith'

[mnboos]

There's obviously something the style parser is not expecting. Probably just something missing in the implementation and looking at your stacktrace (thanks for that!), that's not a big thing to fix.

[mnboos]

Sorry for the delay @tomchadwin

This is caused by a paint object like this:

            "paint": {
                "fill-color": [
                    "match",
                    [
                        "get",
                        "type"
                    ],
                    "Air Transport",
                    "#e6e6e6",
                    "Education",
                    "#f7eaca",
                    "Medical Care",
                    "#f3d8e7",
                    "Road Transport",
                    "#f7f3ca",
                    "Water Transport",
                    "#d8e6f3",
                    "hsl(55, 74%, 88%)"
                ],
                "fill-opacity": 0.6
            }

[tomchadwin]

Is the issue as broad as that match is not implemented at all, or is it more specific than that?

[mnboos]

Correct. I fear the implementation of the style converter is a neverending story and its architecture is far from optimal. On the other hand, a well working converter would be a really nice feature.

Somebody any ideas or hints regarding the architecture of such a piece of code?

cc: @sfkeller