Use std::optional and upgrade to C++20

.clang-format

@@ -111,7 +111,7 @@ SpacesInContainerLiterals: true
 SpacesInCStyleCastParentheses: false
 SpacesInParentheses: false
 SpacesInSquareBrackets: false
-Standard:        c++17
+Standard:        c++20
 TabWidth:        4
 UseTab:          Never
 ...

.github/workflows/cmake.yml

@@ -8,23 +8,32 @@ on:
 
 env:
   # Customize the CMake build type here (Release, Debug, RelWithDebInfo, etc.)
-  BUILD_TYPE: Release
+  BUILD_TYPE: Debug
 
 jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-20.04, ubuntu-22.04]
-
-    runs-on: ${{ matrix.os }}
+        config: [
+          { os: ubuntu-20.04, c_compiler: gcc-10, cpp_compiler: g++-10 },
+          { os: ubuntu-20.04, c_compiler: clang-12, cpp_compiler: clang-12 },
+          { os: ubuntu-22.04, c_compiler: gcc-11, cpp_compiler: g++-11 },
+          { os: ubuntu-22.04, c_compiler: gcc-12, cpp_compiler: g++-12 },
+          { os: ubuntu-22.04, c_compiler: gcc-13, cpp_compiler: g++-13 },
+          { os: ubuntu-20.04, c_compiler: clang-13, cpp_compiler: clang-13 },
+          { os: ubuntu-20.04, c_compiler: clang-14, cpp_compiler: clang-14 },
+          { os: ubuntu-20.04, c_compiler: clang-15, cpp_compiler: clang-15 },
+        ]
+
+    runs-on: ${{ matrix.config.os }}
 
     steps:
     - uses: actions/checkout@v3
 
     - name: Configure CMake
       # Configure CMake in a 'build' subdirectory. `CMAKE_BUILD_TYPE` is only required if you are using a single-configuration generator such as make.
       # See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html?highlight=cmake_build_type
-      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}
+      run: cmake -B ${{github.workspace}}/build -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}} -DCMAKE_C_COMPILER=${{matrix.config.c_compiler}} -DCMAKE_CXX_COMPILER=${{matrix.config.cpp_compiler}}
 
     - name: Build
       # Build your program with the given configuration

.gitignore

@@ -1,9 +1,3 @@
-# The typical build output directory
-/build/
-
-# Sub-projects
-/subprojects/
-
 # Compilation database
 compile_commands.json
 .clangd/

CMakeLists.txt

@@ -1,6 +1,6 @@
 cmake_minimum_required(VERSION 3.10)
 project(libdjinterop
-        VERSION 0.21.0
+        VERSION 0.22.0
         DESCRIPTION "C++ library providing access to DJ record libraries")
 set(PROJECT_HOMEPAGE_URL "https://github.com/xsco/libdjinterop")
 
@@ -15,8 +15,8 @@ if(POLICY CMP0076)
     cmake_policy(SET CMP0076 NEW)
 endif()
 
-# Require C++17
-set(CMAKE_CXX_STANDARD 17)
+# Require C++20
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED True)
 if(MSVC)
     add_compile_options("/W4" "/wd4251" "/wd4275" "$<$<CONFIG:RELEASE>:/O2>")
@@ -27,6 +27,13 @@ else()
     add_compile_options("$<$<CONFIG:DEBUG>:-Wall>")
 endif()
 
+# Public headers rely on the __cplusplus macro being populated correctly.
+# It can be useful to know exactly what it evaluates to.
+try_run(CPP_MACRO_PRINT_COMPILE_RESULT CPP_MACRO_PRINT_RUN_RESULT
+        "${CMAKE_CURRENT_BINARY_DIR}"
+        "${CMAKE_CURRENT_LIST_DIR}/cmake/cplusplus_macro_print.cpp"
+        RUN_OUTPUT_VARIABLE CPP_MACRO_PRINT_OUTPUT)
+message(STATUS "${CPP_MACRO_PRINT_OUTPUT}")
 
 # Build shared a library by default.
 option(BUILD_SHARED_LIBS "Build shared library" ON)
@@ -101,10 +108,6 @@ if(DJINTEROP_LIBRARY_TYPE STREQUAL "STATIC_LIBRARY")
 endif()
 
 # Generate config.hpp based on build-time environment.
-include(CheckIncludeFileCXX)
-CHECK_INCLUDE_FILE_CXX(optional DJINTEROP_STD_OPTIONAL)
-CHECK_INCLUDE_FILE_CXX(experimental/optional DJINTEROP_STD_EXPERIMENTAL_OPTIONAL)
-
 configure_file(
     include/djinterop/config.hpp.in
     include/djinterop/config.hpp)
@@ -170,7 +173,6 @@ install(FILES
     include/djinterop/djinterop.hpp
     include/djinterop/exceptions.hpp
     include/djinterop/musical_key.hpp
-    include/djinterop/optional.hpp
     include/djinterop/pad_color.hpp
     include/djinterop/performance_data.hpp
     include/djinterop/semantic_version.hpp

cmake/cplusplus_macro_print.cpp

@@ -0,0 +1,7 @@
+#include <iostream>
+
+int main()
+{
+    std::cout << "Value of __cplusplus macro: " << __cplusplus;
+    return 0;
+}

example/engine_prime.cpp

@@ -54,7 +54,7 @@ int main()
     td.year = 1970;
     td.title = "Some Song"s;
     td.artist = "Some Artist"s;
-    td.publisher = djinterop::stdx::nullopt;  // indicates missing metadata
+    td.publisher = std::nullopt;  // indicates missing metadata
     td.key = djinterop::musical_key::a_minor;
     td.bitrate = 320;
     td.rating = 60;             // note: rating is in the range 0-100

include/djinterop/album_art.hpp

@@ -19,8 +19,8 @@
 #ifndef DJINTEROP_ALBUM_ART_HPP
 #define DJINTEROP_ALBUM_ART_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <cstdint>
@@ -33,7 +33,7 @@ namespace djinterop
 class album_art
 {
 public:
-    typedef uint_least8_t image_data_type;
+    using image_data_type = uint_least8_t;
 
     std::string hash_hex_str;
     std::vector<image_data_type> image_data;

include/djinterop/config.hpp.in

@@ -19,8 +19,8 @@
 #ifndef DJINTEROP_CONFIG_HPP
 #define DJINTEROP_CONFIG_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 // Statement about whether the library was built/installed as static or shared.
@@ -55,12 +55,6 @@
 #endif  // DJINTEROP_SOURCE
 #define DJINTEROP_LOCAL DJINTEROP_SYMBOL_LOCAL
 
-// Symbols defined after this point represent the environment at the time
-// that this library was built.  The environment when this library is used must
-// be compatible in order to use the library successfully.
-#cmakedefine DJINTEROP_STD_OPTIONAL
-#cmakedefine DJINTEROP_STD_EXPERIMENTAL_OPTIONAL
-
 #include <cstddef>
 static_assert(sizeof(std::byte) == 1,
               "Only platforms where sizeof(std::byte) == 1 are supported");

include/djinterop/crate.hpp

@@ -1,13 +1,15 @@
 /*
-    Tdd!his file is part of libdjinterop.
-dd!
-    ldd!ibdjinterop is free software: you can redistribute it and/or modify
-    idd!t under the terms of the GNU Lesser General Public License as published
-by tdd!he Free Software Foundation, either version 3 of the License, or (dd!at
-your option) any later version. dd! ldd!ibdjinterop is distributed in the hope
-that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
-warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-Lesser General Public License for more details.
+    This file is part of libdjinterop.
+
+    libdjinterop is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    libdjinterop is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
 
     You should have received a copy of the GNU Lesser General Public License
     along with libdjinterop.  If not, see <http://www.gnu.org/licenses/>.
@@ -17,17 +19,17 @@ Lesser General Public License for more details.
 #ifndef DJINTEROP_CRATE_HPP
 #define DJINTEROP_CRATE_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <string>
 #include <vector>
 
 #include <djinterop/config.hpp>
-#include <djinterop/optional.hpp>
 
 namespace djinterop
 {
@@ -118,7 +120,7 @@ class DJINTEROP_PUBLIC crate
     ///
     /// If the crate doesn't have a parent, then `djinterop::nullopt` is
     /// returned.
-    stdx::optional<crate> parent() const;
+    std::optional<crate> parent() const;
 
     /// Removes a track from the crate
     ///
@@ -133,15 +135,15 @@ class DJINTEROP_PUBLIC crate
     ///
     /// If `djinterop::nullopt` is given, then this crate will have no parent.
     /// That is, it becomes a root crate.
-    void set_parent(stdx::optional<crate> parent) const;
+    void set_parent(std::optional<crate> parent) const;
 
     /// Gets the sub-crate of this one with a given name.
     ///
     /// Note that descendants of sub-crates are not found by this method, i.e.
     /// the search does not recurse into the immediate sub-crates of this crate.
     ///
     /// If no such crate is found, then `djinterop::nullopt` is returned.
-    stdx::optional<crate> sub_crate_by_name(const std::string& name) const;
+    std::optional<crate> sub_crate_by_name(const std::string& name) const;
 
     /// Returns the crate's contained tracks.
     ///

include/djinterop/database.hpp

@@ -19,18 +19,18 @@
 #ifndef DJINTEROP_DATABASE_HPP
 #define DJINTEROP_DATABASE_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <stdexcept>
 #include <string>
 #include <vector>
 
 #include <djinterop/config.hpp>
-#include <djinterop/optional.hpp>
 
 namespace djinterop
 {
@@ -55,9 +55,9 @@ class DJINTEROP_PUBLIC database
 
     /// Returns the crate with the given ID
     ///
-    /// If no such crate exists in the database, then `djinterop::stdx::nullopt`
+    /// If no such crate exists in the database, then `std::nullopt`
     /// is returned.
-    stdx::optional<crate> crate_by_id(int64_t id) const;
+    std::optional<crate> crate_by_id(int64_t id) const;
 
     /// Returns all crates contained in the database
     std::vector<crate> crates() const;
@@ -104,8 +104,8 @@ class DJINTEROP_PUBLIC database
 
     /// Returns the root-level crate with the given name.
     ///
-    /// If no such crate exists, then `djinterop::stdx::nullopt` is returned.
-    stdx::optional<crate> root_crate_by_name(const std::string& name) const;
+    /// If no such crate exists, then `std::nullopt` is returned.
+    std::optional<crate> root_crate_by_name(const std::string& name) const;
 
     /// Returns all root crates contained in the database
     ///
@@ -114,9 +114,9 @@ class DJINTEROP_PUBLIC database
 
     /// Returns the track with the given id
     ///
-    /// If no such track exists in the database, then `djinterop::stdx::nullopt`
+    /// If no such track exists in the database, then `std::nullopt`
     /// is returned.
-    stdx::optional<track> track_by_id(int64_t id) const;
+    std::optional<track> track_by_id(int64_t id) const;
 
     /// Returns all tracks whose `relative_path` attribute in the database
     /// matches the given string

include/djinterop/djinterop.hpp

@@ -19,8 +19,8 @@
 #ifndef DJINTEROP_DJINTEROP_HPP
 #define DJINTEROP_DJINTEROP_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <djinterop/album_art.hpp>

include/djinterop/engine/engine.hpp

@@ -19,8 +19,8 @@
 #ifndef DJINTEROP_ENGINE_ENGINE_HPP
 #define DJINTEROP_ENGINE_ENGINE_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <array>

include/djinterop/engine/engine_version.hpp

@@ -19,8 +19,8 @@
 #ifndef DJINTEROP_ENGINE_ENGINE_VERSION_HPP
 #define DJINTEROP_ENGINE_ENGINE_VERSION_HPP
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <ostream>

include/djinterop/engine/v2/beat_data_blob.hpp

@@ -17,8 +17,8 @@
 
 #pragma once
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <cstddef>
@@ -28,9 +28,6 @@
 #include <vector>
 
 #include <djinterop/config.hpp>
-#include <djinterop/optional.hpp>
-#include <djinterop/pad_color.hpp>
-#include <djinterop/performance_data.hpp>
 
 namespace djinterop::engine::v2
 {
@@ -90,7 +87,7 @@ struct DJINTEROP_PUBLIC beat_grid_marker_blob
 struct DJINTEROP_PUBLIC beat_data_blob
 {
     /// Type of collection of beat grid markers.
-    typedef std::vector<beat_grid_marker_blob> beat_grid_marker_blobs_type;
+    using beat_grid_marker_blobs_type = std::vector<beat_grid_marker_blob>;
 
     /// Sample rate, in hertz.
     double sample_rate;

include/djinterop/engine/v2/change_log_table.hpp

@@ -17,16 +17,16 @@
 
 #pragma once
 
-#if __cplusplus < 201703L
-#error This library needs at least a C++17 compliant compiler
+#if __cplusplus < 202002L
+#error This library needs at least a C++20 compliant compiler
 #endif
 
 #include <cstdint>
 #include <memory>
+#include <optional>
 #include <vector>
 
 #include <djinterop/config.hpp>
-#include <djinterop/optional.hpp>
 
 namespace djinterop::engine::v2
 {
@@ -86,7 +86,7 @@ class DJINTEROP_PUBLIC change_log_table
     /// Get the most recent entry in the changelog.
     ///
     /// \return Returns the last entry.
-    [[nodiscard]] djinterop::stdx::optional<change_log_row> last() const;
+    [[nodiscard]] std::optional<change_log_row> last() const;
 
 private:
     std::shared_ptr<engine_library_context> context_;