[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, 15 insertions, 0 deletions

diff --git a/src/mbgl/style/expression/let.cpp b/src/mbgl/style/expression/let.cpp
index fe48138ac3..242a995b0b 100644
--- a/src/mbgl/style/expression/let.cpp
+++ b/src/mbgl/style/expression/let.cpp
@@ -65,6 +65,17 @@ ParseResult Let::parse(const Convertible& value, ParsingContext& ctx) {
     return ParseResult(std::make_unique<Let>(std::move(bindings_), std::move(*result_)));
 }
 
+mbgl::Value Let::serialize() const {
+    std::vector<mbgl::Value> serialized;
+    serialized.emplace_back(getOperator());
+    for (auto entry : bindings) {
+        serialized.emplace_back(entry.first);
+        serialized.emplace_back(entry.second->serialize());
+    }
+    serialized.emplace_back(result->serialize());
+    return serialized;
+}
+
 EvaluationResult Var::evaluate(const EvaluationContext& params) const {
     return value->evaluate(params);
 }
@@ -95,6 +106,10 @@ ParseResult Var::parse(const Convertible& value_, ParsingContext& ctx) {
     return ParseResult(std::make_unique<Var>(name_, std::move(*bindingValue)));
 }
 
+mbgl::Value Var::serialize() const {
+    return std::vector<mbgl::Value>{{ getOperator(), name }};
+}
+
 } // namespace expression
 } // namespace style
 } // namespace mbgl