add in-memory includes via include_template

src/inja.hpp

@@ -614,6 +614,10 @@ class Parser {
 public:
 	ElementNotation element_notation = ElementNotation::Pointer;
 
+	std::map<Parsed::CallbackSignature, Regex, std::greater<Parsed::CallbackSignature>> regex_map_callbacks;
+
+	std::map<const std::string, Template> included_templates;
+
 	/*!
 	@brief create a corresponding regex for a function name with a number of arguments seperated by ,
 	*/
@@ -704,8 +708,6 @@ public:
 		{Parsed::Function::ReadJson, Regex{"\\s*([^\\(\\)]*\\S)\\s*"}}
 	};
 
-	std::map<Parsed::CallbackSignature, Regex, std::greater<Parsed::CallbackSignature>> regex_map_callbacks;
-
 	Parser() { }
 
 	Parsed::ElementExpression parse_expression(const std::string& input) {
@@ -859,11 +861,16 @@ public:
 							break;
 						}
 						case Parsed::Statement::Include: {
-							std::string included_filename = path + match_statement.str(1);
-							Template included_template = parse_template(included_filename);
-							for (auto& element: included_template.parsed_template().children) {
-								result.emplace_back(element);
+							std::string template_name = match_statement.str(1);
+							Template included_template;
+							if (included_templates.find( template_name ) != included_templates.end()) {
+								included_template = included_templates[template_name];
+							} else {
+								included_template = parse_template(path + template_name);
 							}
+
+							auto children = included_template.parsed_template().children;
+							result.insert(result.end(), children.begin(), children.end());
 							break;
 						}
 					}
@@ -1022,6 +1029,10 @@ public:
 		renderer.map_callbacks[signature] = callback;
 	}
 
+	void include_template(std::string name, const Template& temp) {
+		parser.included_templates[name] = temp;
+	}
+
 	template<typename T = json>
 	T get_argument(const Parsed::Arguments& args, int index, const json& data) {
 		return renderer.eval_expression<T>(args[index], data);