JSON parsing changes from new product query

Eliminates need for default constructor

Author: beojan

phlex/configuration.cpp

@@ -1,8 +1,57 @@
 #include "phlex/configuration.hpp"
 #include "phlex/core/product_query.hpp"
+#include "phlex/model/product_specification.hpp"
 
-#include <ranges>
+#include <algorithm>
+#include <array>
 #include <string>
+#include <string_view>
+
+namespace {
+  [[maybe_unused]] std::optional<std::string> value_if_exists(boost::json::object const& obj, // will be used later for new product_query
+                                                              std::string_view parameter)
+  {
+    if (!obj.contains(parameter)) {
+      return std::nullopt;
+    }
+    auto const& val = obj.at(parameter);
+    if (!val.is_string()) {
+      std::string_view kind;
+      switch (val.kind()) {
+      case boost::json::kind::null:
+        // seems reasonable to interpret this as if the value were not provided
+        return std::nullopt;
+        break;
+      case boost::json::kind::bool_:
+        kind = "bool";
+        break;
+      case boost::json::kind::int64:
+        kind = "std::int64_t";
+        break;
+      case boost::json::kind::uint64:
+        kind = "std::uint64_t";
+        break;
+      case boost::json::kind::double_:
+        kind = "double";
+        break;
+      case boost::json::kind::array:
+        kind = "array";
+        break;
+      case boost::json::kind::object:
+        kind = "object";
+        break;
+      default:
+        // std::unreachable();
+        break;
+      }
+      throw std::runtime_error(
+        fmt::format("Error retrieving parameter '{}'. Should be a string but is instead a {}",
+                    parameter,
+                    kind));
+    }
+    return boost::json::value_to<std::string>(val);
+  }
+}
 
 namespace phlex {
   std::vector<std::string> configuration::keys() const
@@ -25,7 +74,8 @@ namespace phlex {
   {
     using detail::value_decorate_exception;
     auto query_object = jv.as_object();
-    return product_query{{value_decorate_exception<std::string>(query_object, "product")},
-                         value_decorate_exception<std::string>(query_object, "layer")};
+    auto product = value_decorate_exception<std::string>(query_object, "product");
+    auto layer = value_decorate_exception<std::string>(query_object, "layer");
+    return product_query{experimental::product_specification::create(product), layer};
   }
 }

phlex/configuration.hpp

@@ -19,6 +19,14 @@ namespace phlex {
     } catch (std::exception const& e) {
       throw std::runtime_error("Error retrieving parameter '" + key + "':\n" + e.what());
     }
+
+    // helper for unpacking json array
+    template <typename T, std::size_t... I>
+    std::array<T, sizeof...(I)> unpack_json_array(boost::json::array const& array,
+                                                  std::index_sequence<I...>)
+    {
+      return std::array<T, sizeof...(I)>{boost::json::value_to<T>(array.at(I))...};
+    }
   }
 
   class configuration {
@@ -81,6 +89,19 @@ namespace phlex {
 
   product_query tag_invoke(boost::json::value_to_tag<product_query> const&,
                            boost::json::value const& jv);
+
+  template <std::size_t N>
+  std::array<product_query, N> tag_invoke(
+    boost::json::value_to_tag<std::array<product_query, N>> const&, boost::json::value const& jv)
+  {
+    auto const& array = jv.as_array();
+    return detail::unpack_json_array<product_query>(array, std::make_index_sequence<N>());
+  }
 }
 
+// The below is a better long term fix but it requires a Boost JSON bug (#1140) to be fixed
+// namespace boost::json {
+//   template <std::size_t N>
+//   struct is_sequence_like<std::array<phlex::product_query, N>> : std::false_type {};
+// }
 #endif // PHLEX_CONFIGURATION_HPP

phlex/core/product_query.cpp

@@ -5,8 +5,6 @@
 #include <stdexcept>
 
 namespace phlex {
-  product_query::product_query() = default;
-
   product_query::product_query(experimental::product_specification spec, std::string layer) :
     spec_{std::move(spec)}, layer_{std::move(layer)}
   {

phlex/core/product_query.hpp

@@ -10,9 +10,6 @@
 namespace phlex {
   class product_query {
   public:
-    // FIXME: Boost JSON's parameter retrieval facilities require a default constructor
-    //        whenever the type is (e.g.) std::array<product_query, N>.
-    product_query();
     product_query(experimental::product_specification spec, std::string layer);
 
     auto const& spec() const noexcept { return spec_; }