Ruby reserved words in filters

[nebulon42]

I'm using a datasource (http://osm2vectortiles.org), which makes extensive use of the column name "class". Using this in filters leads to errors. I think this has something to do with "class" being a reserved word. But also writing on('class'=='residential') yields the following error:

    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:244:in `_set_filter'
    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:200:in `on'
    from (eval):11:in `block (2 levels) in <main>'
    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:89:in `instance_eval'
    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:89:in `layer'
    from (eval):5:in `block in <main>'
    from ../glug/bin/glug:5:in `instance_eval'
    from ../glug/bin/glug:5:in `block in <main>'
    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:71:in `instance_eval'
    from /var/lib/gems/1.9.1/gems/glug-0.0.2/lib/glug.rb:71:in `initialize'
    from ../glug/bin/glug:5:in `new'
    from ../glug/bin/glug:5:in `<main>'

Is there another way of using reserved words I'm missing or does something in the code of Glug need changing? @systemed

[nebulon42]

By looking at the code I was not able to find out how the arguments to the on() function are parsed. It seems that when the first part of the filter expression is either a variable, a reserved word or a string this evaluates to false otherwise to a proper Condition.

[systemed]

Glug uses method_missing to interpret conditions. As you've spotted, this won't work where the 'key' is a Ruby reserved word and therefore not missing!

As a workaround, you can define the key as an object explicitly:

_class = Glug::OSMKey.new('class')

and then refer to it from then onwards like this:

on(_class=='residential')

Going forward, I think the best way to solve this would be a short-form version of the above, where you could write tag('class')=='residential' where a reserved word was needed.

[nebulon42]

Thanks for the explanation! Your workaround did it for me.

[nebulon42]

Fixed in 0a20718.
Can now write e.g. on(tag('class')=='residential').

[systemed]

Advance warning: this will change to get('class') in the next version of Glug, for consistency with MBGL expressions.