Filters

[miki725]

Sometimes filters are desired:

path.to.node.<lookup>

the lookup will not be executed if node lookup will fail (e.g. not present). simplepath should provided a filter which will execute no matter if any intermediate nodes blow up. possible syntax:

path.to.node|<lookup>

[miki725]

another alternative is allow to do conditional filters. syntax is inspired by javascript:

path.to.node?<success>:<failure>

so success lookup will execute when all previous lookups succeed or failure will execute if something blew up

[miki725]

actually this is partially possible currently in simplepath:

Expression('path.to.node.<yesno:success,failure>', default='failure')

[ashishgore]

Conditional filters can be extended. In addition to lookups, if we can provide a way to find key(s) in an order and return back with the first match found, that would solve a use case for label customization. Example:

path.to.node1 or path.to.node2 or path.to.node3

The 'or' operator will behave like a if..else condition going from left to right. The first non-null value should be returned back.