json_writer_boost and json_writer_nlohmann

Author: zajo

.vscode/tasks.json

@@ -1,6 +1,4 @@
 {
-    // See https://go.microsoft.com/fwlink/?LinkId=733558
-    // for the documentation about the tasks.json format
     "version": "2.0.0",
     "tasks": [
         {
@@ -90,7 +88,8 @@
                 "Generate leaf.hpp",
                 "Download nlohmann/json.hpp"
             ],
-            "command": "cd ${workspaceRoot}/_bld/debug && ninja && meson test && cd ${workspaceRoot}/_bld/debug && ninja && meson test",
+            "dependsOrder": "sequence",
+            "command": "cd ${workspaceRoot}/_bld/debug && ninja && meson test && cd ${workspaceRoot}/_bld/debug_single_header && ninja && meson test",
             "problemMatcher": {
                 "base": "$gcc",
                 "fileLocation": [
@@ -116,6 +115,7 @@
                 "Generate leaf.hpp",
                 "Download nlohmann/json.hpp"
             ],
+            "dependsOrder": "sequence",
             "command": "cd ${workspaceRoot}/_bld/release && ninja && meson test && cd ${workspaceRoot}/_bld/release_single_header && ninja && meson test",
             "problemMatcher": {
                 "base": "$gcc",
@@ -142,6 +142,7 @@
                 "Generate leaf.hpp",
                 "Download nlohmann/json.hpp"
             ],
+            "dependsOrder": "sequence",
             "command": "../../b2 --abbreviate-paths test link=shared,static variant=debug,release,leaf_debug_diag0,leaf_release_diag0,leaf_debug_single_header,leaf_release_single_header,leaf_debug_embedded,leaf_release_embedded exception-handling=off rtti=off cxxstd=11,14,1z,17 && ../../b2 --abbreviate-paths test link=shared,static variant=debug,release,leaf_debug_diag0,leaf_release_diag0,leaf_debug_single_header,leaf_release_single_header exception-handling=on,off cxxstd=11,14,1z,17",
             "problemMatcher": {
                 "base": "$gcc",
@@ -168,10 +169,7 @@
             },
             "label": "Test current editor file",
             "type": "shell",
-            "command": "cd ${workspaceRoot}/_bld/debug && ninja && { meson test ${fileBasenameNoExtension} || cat ./meson-logs/testlog.txt; }",,
-            "windows": {
-                "command": "cd ${workspaceRoot}/_bld/debug && ninja && (meson test ${fileBasenameNoExtension} || type .\\meson-logs\\testlog.txt)",
-            },
+            "command": "cd ${workspaceRoot}/_bld/debug && ninja && { meson test ${fileBasenameNoExtension} || cat ./meson-logs/testlog.txt; }",
             "problemMatcher": {
                 "base": "$gcc",
                 "fileLocation": [

doc/leaf.adoc

@@ -1813,28 +1813,28 @@ To support multiple output formats, pass multiple functions to `h.dispatch`:
 [source,c++]
 ----
 h.dispatch(
-  [&](nlohmann_writer & nw) { write_nested(nw, e, name); },
+  [&](json_writer_nlohmann & w) { write_nested(w, e, name); },
   [&](xml_writer & xw) { write_nested(xw, e, name); }
 );
 ----
 
 ==== JSON Serialization
 
-LEAF provides `nlohmann_writer`, a class template for JSON serialization. The `nlohmann_writer` class defines `write` and `write_nested` friend functions (see <<tutorial-serialization>>) that work with:
+LEAF provides writers for JSON serialization with two popular JSON libraries:
 
-* Types for which `to_json` overloads can be found via ADL
-* Types for which a `write` overload can be found via ADL (e.g. LEAF types)
+* <<json_writer_nlohmann>> for https://github.com/nlohmann/json[nlohmann/json]
+* <<json_writer_boost>> for https://www.boost.org/doc/libs/release/libs/json/[Boost.JSON]
 
-This interface is compatible with https://github.com/nlohmann/json[nlohmann/json], we just need to define the required `serialize` function template (see <<custom-writers>>):
+Below is an example using `json_writer_nlohmann`. We just need to define the required `serialize` function template (see <<custom-writers>>):
 
 [source,c++]
 ----
-#include <boost/leaf/serialization/nlohmann_writer.hpp>
+#include <boost/leaf/serialization/json_writer_nlohmann.hpp>
 #include "nlohmann/json.hpp"
 
 namespace leaf = boost::leaf;
 
-using nlohmann_writer = leaf::serialization::nlohmann_writer<nlohmann::json>;
+using json_writer_nlohmann = leaf::serialization::json_writer_nlohmann<nlohmann::json>;
 
 namespace boost { namespace leaf {
 
@@ -1843,8 +1843,8 @@ namespace serialization {
   template <class Handle, class E>
   void serialize(Handle & h, E const & e, char const * name)
   {
-    h.dispatch([&](nlohmann_writer & nw) {
-      write_nested(nw, e, name);
+    h.dispatch([&](json_writer_nlohmann & w) {
+      write_nested(w, e, name);
     });
   }
 
@@ -1886,7 +1886,7 @@ leaf::try_handle_all(
   [](leaf::diagnostic_details const & dd)
   {
     nlohmann::json j;
-    nlohmann_writer w(j);
+    json_writer_nlohmann w(j);
     dd.write_to(w);
     std::cout << j.dump(2) << std::endl;
   }
@@ -2867,36 +2867,68 @@ Reference: <<to_variant>>
 
 === Serialization
 
-[[nlohmann_writer.hpp]]
-==== `nlohmann_writer.hpp`
+[[json_writer_boost.hpp]]
+==== `json_writer_boost.hpp`
 
 ====
-.#include <boost/leaf/serialization/nlohmann_writer.hpp>
+.#include <boost/leaf/serialization/json_writer_boost.hpp>
+[source,c++]
+----
+namespace boost { namespace leaf {
+
+namespace serialization
+{
+  struct json_writer_boost
+  {
+    boost::json::value & v_;
+
+    // Enabled if x is assignable to boost::json::value, or
+    // if tag_invoke is defined for boost::json::value_from_tag.
+    template <class T>
+    friend void write( json_writer_boost &, T const & x );
+
+    template <class T>
+    friend void write_nested( json_writer_boost &, T const &, char const * name );
+  };
+}
+
+} }
+----
+
+[.text-right]
+Reference: <<json_writer_boost>>
+====
+
+[[json_writer_nlohmann.hpp]]
+==== `json_writer_nlohmann.hpp`
+
+====
+.#include <boost/leaf/serialization/json_writer_nlohmann.hpp>
 [source,c++]
 ----
 namespace boost { namespace leaf {
 
 namespace serialization
 {
   template <class Json>
-  struct nlohmann_writer
+  struct json_writer_nlohmann
   {
     Json & j_;
 
+    // Enabled if to_json is defined for Json and T.
     template <class T>
-    friend auto write( nlohmann_writer &, T const & x )
-      -> decltype(to_json(std::declval<Json &>(), x));
+    friend void write( json_writer_nlohmann &, T const & x );
 
     template <class T>
-    friend void write_nested( nlohmann_writer &, T const &, char const * name );
+    friend void write_nested( json_writer_nlohmann &, T const &, char const * name );
   };
 }
 
 } }
 ----
 
 [.text-right]
-Reference: <<nlohmann_writer>>
+Reference: <<json_writer_nlohmann>>
 ====
 
 [[functions]]
@@ -4442,36 +4474,70 @@ The `write_to` member function is used with the serialization system; see <<tuto
 
 '''
 
-[[nlohmann_writer]]
-=== `nlohmann_writer`
+[[json_writer_boost]]
+=== `json_writer_boost`
+
+.#include <boost/leaf/serialization/json_writer_boost.hpp>
+[source,c++]
+----
+namespace boost { namespace leaf {
+
+namespace serialization
+{
+  struct json_writer_boost
+  {
+    boost::json::value & v_;
+
+    // Enabled if x is assignable to boost::json::value, or
+    // if tag_invoke is defined for boost::json::value_from_tag.
+    template <class T>
+    friend void write( json_writer_boost &, T const & x );
+
+    template <class T>
+    friend void write_nested( json_writer_boost &, T const &, char const * name );
+  };
+}
+
+} }
+----
+
+The `json_writer_boost` type serializes error objects to JSON format using https://www.boost.org/doc/libs/release/libs/json/[Boost.JSON]. The `write` function is enabled for:
+
+* Types directly assignable to `boost::json::value`
+* Types for which a `tag_invoke` overload for `value_from_tag` can be found via ADL
+
+See <<tutorial-serialization>>.
+
+'''
+
+[[json_writer_nlohmann]]
+=== `json_writer_nlohmann`
 
-.#include <boost/leaf/serialization/nlohmann_writer.hpp>
+.#include <boost/leaf/serialization/json_writer_nlohmann.hpp>
 [source,c++]
 ----
 namespace boost { namespace leaf {
 
 namespace serialization
 {
   template <class Json>
-  struct nlohmann_writer
+  struct json_writer_nlohmann
   {
     Json & j_;
 
-    // Enabled for types for which a suitable to_json overload
-    // can be found via ADL, but a suitable write overload cannot.
+    // Enabled if to_json is defined for Json and T.
     template <class T>
-    friend auto write( nlohmann_writer &, T const & x )
-      -> decltype(to_json(std::declval<Json &>(), x));
+    friend void write( json_writer_nlohmann &, T const & x );
 
     template <class T>
-    friend void write_nested( nlohmann_writer &, T const &, char const * name );
+    friend void write_nested( json_writer_nlohmann &, T const &, char const * name );
   };
 }
 
 } }
 ----
 
-The `nlohmann_writer` class template serializes error objects to JSON format using unqualified calls to `to_json`. This is compatible with https://github.com/nlohmann/json[nlohmann/json]; See <<tutorial-serialization>>.
+The `json_writer_nlohmann` serializes error objects to JSON format using unqualified calls to `to_json`. This is compatible with https://github.com/nlohmann/json[nlohmann/json]; See <<tutorial-serialization>>.
 
 '''
 

include/boost/leaf/detail/all.hpp

@@ -11,5 +11,6 @@
 #include <boost/leaf/on_error.hpp>
 #include <boost/leaf/pred.hpp>
 #include <boost/leaf/result.hpp>
-#include <boost/leaf/serialization/nlohmann_writer.hpp>
+#include <boost/leaf/serialization/json_writer_boost.hpp>
+#include <boost/leaf/serialization/json_writer_nlohmann.hpp>
 #include <boost/leaf/to_variant.hpp>

include/boost/leaf/serialization/json_writer_boost.hpp

@@ -0,0 +1,53 @@
+#ifndef BOOST_LEAF_SERIALIZATION_JSON_WRITER_BOOST_HPP_INCLUDED
+#define BOOST_LEAF_SERIALIZATION_JSON_WRITER_BOOST_HPP_INCLUDED
+
+// Copyright 2018-2026 Emil Dotchevski and Reverge Studios, Inc.
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+#include <utility>
+
+namespace boost { namespace json {
+
+class value;
+struct value_from_tag;
+
+} }
+
+namespace boost { namespace leaf {
+
+namespace serialization
+{
+    template <class Value = boost::json::value, class ValueFromTag = boost::json::value_from_tag>
+    struct json_writer_boost_
+    {
+        Value & v_;
+
+        template <class T>
+        friend auto write(json_writer_boost_ & w, T const & x) -> decltype(std::declval<Value &>() = x, void())
+        {
+            w.v_ = x;
+        }
+
+        template <class T>
+        friend auto write(json_writer_boost_ & w, T const & x) -> decltype(tag_invoke(std::declval<ValueFromTag>(), std::declval<Value &>(), x), void())
+        {
+            tag_invoke(ValueFromTag{}, w.v_, x);
+        }
+
+        template <class T>
+        friend void write_nested(json_writer_boost_ & w, T const & x, char const * name)
+        {
+            if( w.v_.is_null() )
+                w.v_.emplace_object();
+            json_writer_boost_ nested{w.v_.as_object()[name]};
+            write(nested, x);
+        }
+    };
+
+    using json_writer_boost = json_writer_boost_<>;
+}
+
+} }
+
+#endif

…t/leaf/serialization/nlohmann_writer.hpp …f/serialization/json_writer_nlohmann.hppinclude/boost/leaf/serialization/nlohmann_writer.hpp renamed to include/boost/leaf/serialization/json_writer_nlohmann.hpp include/boost/leaf/serialization/nlohmann_writer.hpp renamed to include/boost/leaf/serialization/json_writer_nlohmann.hpp

@@ -1,5 +1,5 @@
-#ifndef BOOST_LEAF_SERIALIZATION_NLOHMANN_WRITER_HPP_INCLUDED
-#define BOOST_LEAF_SERIALIZATION_NLOHMANN_WRITER_HPP_INCLUDED
+#ifndef BOOST_LEAF_SERIALIZATION_JSON_WRITER_NLOHMANN_HPP_INCLUDED
+#define BOOST_LEAF_SERIALIZATION_JSON_WRITER_NLOHMANN_HPP_INCLUDED
 
 // Copyright 2018-2026 Emil Dotchevski and Reverge Studios, Inc.
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
@@ -12,26 +12,25 @@ namespace boost { namespace leaf {
 namespace serialization
 {
     template <class Json>
-    struct nlohmann_writer
+    struct json_writer_nlohmann
     {
         Json & j_;
 
         template <class T>
-        friend auto write(nlohmann_writer & w, T const & x) -> decltype(to_json(std::declval<Json &>(), x))
+        friend auto write(json_writer_nlohmann & w, T const & x) -> decltype(to_json(std::declval<Json &>(), x), void())
         {
             to_json(w.j_, x);
         }
 
         template <class T>
-        friend void write_nested(nlohmann_writer & w, T const & x, char const * name)
+        friend void write_nested(json_writer_nlohmann & w, T const & x, char const * name)
         {
-            nlohmann_writer nested{w.j_[name]};
+            json_writer_nlohmann nested{w.j_[name]};
             write(nested, x);
         }
     };
-
 }
 
 } }
 
-#endif // #ifndef BOOST_LEAF_SERIALIZATION_NLOHMANN_WRITER_HPP_INCLUDED
+#endif

meson.build

@@ -141,7 +141,7 @@ if option_enable_unit_tests
         'handle_basic_test',
         'handle_some_other_result_test',
         'handle_some_test',
-        'nlohmann_test',
+        'json_writer_nlohmann_test',
         'match_member_test',
         'match_test',
         'match_value_test',
@@ -224,7 +224,7 @@ if option_enable_unit_tests
         '_hpp_on_error_test',
         '_hpp_pred_test',
         '_hpp_result_test',
-        '_hpp_serialization_nlohmann_writer_test',
+        '_hpp_serialization_json_writer_nlohmann_test',
         '_hpp_to_variant_test',
     ]
     foreach t : header_tests

test/Jamfile.v2

@@ -44,7 +44,8 @@ compile _hpp_leaf_test.cpp ;
 compile _hpp_on_error_test.cpp ;
 compile _hpp_pred_test.cpp ;
 compile _hpp_result_test.cpp ;
-compile _hpp_serialization_nlohmann_writer_test.cpp ;
+compile _hpp_serialization_json_writer_nlohmann_test.cpp ;
+compile _hpp_serialization_json_writer_boost_test.cpp ;
 compile _hpp_to_variant_test.cpp ;
 
 run boost_exception_test.cpp ;
@@ -84,7 +85,8 @@ run handle_all_test.cpp ;
 run handle_basic_test.cpp ;
 run handle_some_other_result_test.cpp ;
 run handle_some_test.cpp ;
-run nlohmann_test.cpp : : : <toolset>clang,<target-os>linux,<cxxstd>2b:<build>no <toolset>clang,<target-os>linux,<cxxstd>23:<build>no ;
+run json_writer_nlohmann_test.cpp : : : <toolset>clang,<target-os>linux,<cxxstd>2b:<build>no <toolset>clang,<target-os>linux,<cxxstd>23:<build>no ;
+run json_writer_boost_test.cpp /boost/json//boost_json ;
 run match_member_test.cpp ;
 run match_test.cpp ;
 run match_value_test.cpp ;