Legacy filters aren't part of the style specification, but you can generate them by parsing a legacy filter in a stylesheet, and obtaining the parsed Filter and serializing it.
* Fix crash due to mixing legacy filters and expressions
In some cases, (invalid) nested filters that used a mix of legacy filter
syntax and expression syntax caused a crash due to a failure to
propagate parsing errors from deeper within the filter expression.
These errors went undetected in part because these conversion functions
returned unique_ptr<Expression> values (or vectors thereof), using
{nullptr} to represent a parsing error, but the core expression classes
expect unique_ptr<Expression> that are never null.
This changes over to using expression::ParseResult (aka
optional<unique_ptr<Expression>>), to represent conversion failure
the same way we do in the rest of the expression system.
* Fix clang 3.8 / gcc 4.9 issue
* WIP
* WIP
* WIP
* Remove Filter::operator()(const Feature&)
* WIP
* WIP
* WIP
* WIP
* Hook up expression filter evaluator
* Replace `shared_ptr` with &reference
* Fill in implementation of `void operator()(const ExpressionFilter&)`
* Fix failing tests
* Switch back to a shared_ptr per chat with @anandthakker
* Fix benchmark compilation
* Shot in the dark to fix CI
* Shot in the dark to fix CI (part 2)
* Shot in the dark to fix CI (part 3)
* In src/mbgl/style/conversion/filter.cpp, add a port of isExpressionFilter and use it to decide in Converter<Filter>::operator() whether to parse the incoming JSON as an ExpressionFilter or one of the legacy filter types
* Remove bool Filter::operator()(const GeometryTileFeature&) const
* Ensure the map zoom is passed into filtering operations wherever applicable
* Add expression filter tests
* Addressed PR feedback
* Implement `NSPredicate *operator()(mbgl::style::ExpressionFilter filter)`
* Fix formatting& nit
