feat chaotic: allow SAX parsing of recursive arrays

Tests: протестировано CI
commit_hash:fa31d32d10e3a36018b924d338794174b571077a

Author: apolukhin

chaotic/include/userver/chaotic/sax_parser.hpp

@@ -66,12 +66,12 @@ class WithValidators final : private formats::json::parser::Subscriber<typename
 
     void Subscribe(formats::json::parser::Subscriber<ResultType>& subscriber) { subscriber_ = &subscriber; }
 
-    formats::json::parser::BaseParser& GetParser() { return parser_; }
+    formats::json::parser::BaseParser& GetParser() { return parser_.GetParser(); }
 
 private:
     void OnSend(ResultType&& value) override {
         [[maybe_unused]] const auto error_reporter = [this](std::string_view error) {
-            formats::json::parser::BaseParser& base = parser_;
+            formats::json::parser::BaseParser& base = parser_.GetParser();
             chaotic::ThrowForPath<formats::json::Value>(error, base.GetCurrentPath());
         };
         (Validator::Validate(value, error_reporter), ...);

chaotic/include/userver/chaotic/sax_parser_join.hpp

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <memory>
+
 #include <userver/formats/json/parser/typed_parser.hpp>
 
 USERVER_NAMESPACE_BEGIN
@@ -13,28 +15,33 @@ class JoinedParser final {
 public:
     using ResultType = typename ParserA::ResultType;
 
-    JoinedParser()
-        : main_parser_(subparser_)
-    {}
+    JoinedParser();
+    ~JoinedParser();
 
     void Reset() { main_parser_.Reset(); }
 
     void Subscribe(formats::json::parser::Subscriber<typename ParserA::ResultType>& subscriber) {
         main_parser_.Subscribe(subscriber);
     }
 
-    auto& GetParser() { return main_parser_; }
-
-    operator formats::json::parser::BaseParser&()
-    {
-        return main_parser_;
-    }
+    formats::json::parser::BaseParser& GetParser() { return main_parser_; }
 
 private:
-    ParserB subparser_;
+    // We use std::unique_ptr here to break the circular dependency for recursive types in the same way as it is
+    // implicitly done in DOM.
+    std::unique_ptr<ParserB> subparser_;
     ParserA main_parser_;
 };
 
+template <typename ParserA, typename ParserB>
+JoinedParser<ParserA, ParserB>::JoinedParser()
+    : subparser_(std::make_unique<ParserB>()),
+      main_parser_(*subparser_)
+{}
+
+template <typename ParserA, typename ParserB>
+JoinedParser<ParserA, ParserB>::~JoinedParser() = default;
+
 }  // namespace chaotic::sax
 
 USERVER_NAMESPACE_END

chaotic/integration_tests/schemas/recursion.yaml

@@ -9,3 +9,56 @@ definitions:
                 type: array
                 items:
                     $ref: '#/definitions/RecursiveObject'
+
+    RecursiveEntityA:
+        type: object
+        additionalProperties: false
+        properties:
+            field1:
+                type: array
+                items:
+                    $ref: "#/definitions/RecursiveEntityB"
+            field2:
+                type: array
+                items:
+                    $ref: "#/definitions/RecursiveEntityC"
+
+    RecursiveEntityB:
+        type: object
+        additionalProperties:
+            type: string
+        properties:
+            field3:
+                oneOf:
+                  - type: string
+                  - type: array
+                    items:
+                        type: string
+            field4:
+                type: array
+                items:
+                    type: string
+            field5:
+                type: array
+                items:
+                    $ref: "#/definitions/RecursiveEntityB"
+            field6:
+                type: string
+
+    RecursiveEntityC:
+        type: object
+        additionalProperties:
+            type: string
+        properties:
+            field7:
+                type: string
+            field8:
+                oneOf:
+                  - type: string
+                  - type: array
+                    items:
+                        type: string
+            field9:
+                type: array
+                items:
+                    $ref: "#/definitions/RecursiveEntityC"