[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, 8 insertions, 0 deletions

diff --git a/src/mbgl/style/expression/literal.cpp b/src/mbgl/style/expression/literal.cpp
index 7e79fcbfe6..8a63980dba 100644
--- a/src/mbgl/style/expression/literal.cpp
+++ b/src/mbgl/style/expression/literal.cpp
@@ -102,6 +102,14 @@ ParseResult Literal::parse(const Convertible& value, ParsingContext& ctx) {
     }
 }
 
+mbgl::Value Literal::serialize() const {
+    if (getType().is<type::Array>() || getType().is<type::ObjectType>()) {
+        return std::vector<mbgl::Value>{{ getOperator(), *fromExpressionValue<mbgl::Value>(value) }};
+    } else {
+        return *fromExpressionValue<mbgl::Value>(value);
+    }
+}
+
 } // namespace expression
 } // namespace style
 } // namespace mbgl