[core] Implement Expression::serialize()

Issue #10714
- Each expression stores its operator as a string, and default serialization is [operator, serialize(child1), ...]
- Custom implementations of `serialize` for Expression types that don't follow the pattern
- expression::Value -> mbgl::Value converter
- node_expression bindings to expose `serialize`

1 files changed, 1 insertions, 0 deletions

diff --git a/include/mbgl/style/expression/coalesce.hpp b/include/mbgl/style/expression/coalesce.hpp
index 52d9498cbd..a858bef695 100644
--- a/include/mbgl/style/expression/coalesce.hpp
+++ b/include/mbgl/style/expression/coalesce.hpp
@@ -38,6 +38,7 @@ public:
         return args.at(i).get();
     }
     
+    std::string getOperator() const override { return "coalesce"; }
 private:
     Args args;
 };