[WIP] Modular C++20 modules

Directory.Build.Props

@@ -52,8 +52,9 @@
       <TreatWarningAsError>true</TreatWarningAsError>
       <SDLCheck>true</SDLCheck>
       <ConformanceMode>true</ConformanceMode>
-      <LanguageStandard Condition="'$(CppWinRTLanguageStandard)'==''">stdcpp17</LanguageStandard>
+      <LanguageStandard Condition="'$(CppWinRTLanguageStandard)'=='' Or '$(CppWinRTLanguageStandard)'=='17'">stdcpp17</LanguageStandard>
       <LanguageStandard Condition="'$(CppWinRTLanguageStandard)'=='20'">stdcpp20</LanguageStandard>
+      <LanguageStandard Condition="'$(CppWinRTLanguageStandard)'=='latest'">stdcpplatest</LanguageStandard>
       <PrecompiledHeader>Use</PrecompiledHeader>
       <PrecompiledHeaderFile>pch.h</PrecompiledHeaderFile>
       <PreprocessorDefinitions>CPPWINRT_VERSION_STRING="$(CppWinRTBuildVersion)";%(PreprocessorDefinitions)</PreprocessorDefinitions>

cppwinrt/code_writers.h

@@ -145,6 +145,28 @@ namespace cppwinrt
         }
     }
 
+    static void write_parent_imports(writer& w, cache const& c, std::string_view const& type_namespace)
+    {
+        auto pos = type_namespace.rfind('.');
+
+        if (pos == std::string::npos)
+        {
+            return;
+        }
+
+        auto parent = type_namespace.substr(0, pos);
+        auto found = c.namespaces().find(parent);
+
+        if (found != c.namespaces().end() && has_projected_types(found->second))
+        {
+            w.write_import(parent);
+        }
+        else
+        {
+            write_parent_imports(w, c, parent);
+        }
+    }
+
     static void write_pch(writer& w)
     {
         auto format = R"(#include "%"
@@ -313,11 +335,22 @@ namespace cppwinrt
             return;
         }
 
-        if (type_name == "Windows.Foundation.DateTime" ||
-            type_name == "Windows.Foundation.TimeSpan")
+        if (type_name.name_space == "Windows.Foundation")
         {
-            // Don't forward declare these since they're not structs.
-            return;
+            if (type_name.name == "DateTime" ||
+                type_name.name == "TimeSpan")
+            {
+                // Don't forward declare these since they're not structs.
+                return;
+            }
+
+            if (type_name.name == "Point" ||
+                type_name.name == "Rect" ||
+                type_name.name == "Size")
+            {
+                // Don't forward declare these since they're already defined in base.h.
+                return;
+            }
         }
 
         if (type_name.name_space == "Windows.Foundation.Numerics")
@@ -2812,7 +2845,12 @@ struct WINRT_IMPL_EMPTY_BASES produce_dispatch_to_overridable<T, D, %>
         }
     }
 
-    static bool write_structs(writer& w, std::vector<TypeDef> const& types)
+    struct write_structs_result
+    {
+        bool promote = false;
+    };
+
+    static write_structs_result write_structs(writer& w, std::vector<TypeDef> const& types)
     {
         auto format = R"(    struct %
     {
@@ -2829,7 +2867,7 @@ struct WINRT_IMPL_EMPTY_BASES produce_dispatch_to_overridable<T, D, %>
 
         if (types.empty())
         {
-            return false;
+            return {};
         }
 
         struct complex_struct
@@ -2895,7 +2933,7 @@ struct WINRT_IMPL_EMPTY_BASES produce_dispatch_to_overridable<T, D, %>
             }
         }
 
-        bool promote = false;
+        write_structs_result result;
         auto cpp_namespace = w.write_temp("@", w.type_namespace);
 
         for (auto&& type : structs)
@@ -2921,14 +2959,14 @@ struct WINRT_IMPL_EMPTY_BASES produce_dispatch_to_overridable<T, D, %>
                     continue;
                 }
 
-                if (!starts_with(field.second, cpp_namespace))
+                if (!result.promote && !starts_with(field.second, cpp_namespace))
                 {
-                    promote = true;
+                    result.promote = true;
                 }
             }
         }
 
-        return promote;
+        return result;
     }
 
     static void write_class_requires(writer& w, TypeDef const& type)

cppwinrt/cppwinrt.vcxproj

@@ -65,10 +65,12 @@
     <ClInclude Include="..\strings\base_macros.h" />
     <ClInclude Include="..\strings\base_marshaler.h" />
     <ClInclude Include="..\strings\base_meta.h" />
+    <ClInclude Include="..\strings\base_module.h" />
     <ClInclude Include="..\strings\base_natvis.h" />
     <ClInclude Include="..\strings\base_reference_produce.h" />
     <ClInclude Include="..\strings\base_reference_produce_1.h" />
     <ClInclude Include="..\strings\base_security.h" />
+    <ClInclude Include="..\strings\base_shared.h" />
     <ClInclude Include="..\strings\base_std_hash.h" />
     <ClInclude Include="..\strings\base_string.h" />
     <ClInclude Include="..\strings\base_stringable_format.h" />

cppwinrt/cppwinrt.vcxproj.filters

@@ -106,6 +106,9 @@
     <ClInclude Include="..\strings\base_meta.h">
       <Filter>strings</Filter>
     </ClInclude>
+    <ClInclude Include="..\strings\base_module.h">
+      <Filter>strings</Filter>
+    </ClInclude>
     <ClInclude Include="..\strings\base_natvis.h">
       <Filter>strings</Filter>
     </ClInclude>
@@ -187,6 +190,9 @@
     <ClInclude Include="..\strings\base_stringable_to_hstring.h">
       <Filter>strings</Filter>
     </ClInclude>
+    <ClInclude Include="..\strings\base_shared.h">
+      <Filter>strings</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ResourceCompile Include="$(OutDir)version.rc" />

cppwinrt/file_writers.h

@@ -11,6 +11,7 @@ namespace cppwinrt
             auto wrap_file_guard = wrap_open_file_guard(w, "BASE");
 
             w.write(strings::base_includes);
+            w.write_root_include("shared");
             w.write(strings::base_macros);
             w.write(strings::base_types);
             w.write(strings::base_extern);
@@ -46,6 +47,26 @@ namespace cppwinrt
         w.flush_to_file(settings.output_folder + "winrt/base.h");
     }
 
+    static void write_shared_h()
+    {
+        writer w;
+        write_preamble(w);
+        w.write(strings::base_shared);
+        w.flush_to_file(settings.output_folder + "winrt/shared.h");
+    }
+
+    static void write_base_ixx()
+    {
+        writer ixx;
+        write_preamble(ixx);
+        ixx.write("module;\n");
+        ixx.write(strings::base_includes);
+        ixx.write_root_include("shared");
+        ixx.write(strings::base_module);
+        ixx.write_root_include("base");
+        ixx.flush_to_file(settings.output_folder + "winrt/ixx/base.ixx");
+    }
+
     static void write_fast_forward_h(std::vector<TypeDef> const& classes)
     {
         writer w;
@@ -65,6 +86,48 @@ namespace cppwinrt
         w.flush_to_file(settings.output_folder + "winrt/fast_forward.h");
     }
 
+    static void write_namespace_ixx(cache const& c, writer const& header_writer, std::string_view const& ns, char import_impl, char impl = 0)
+    {
+        writer w;
+        w.type_namespace = ns;
+        write_preamble(w);
+        w.write("module;\n");
+        w.write_root_include("shared");
+        w.write("#define WINRT_EXPORT export\n");
+        w.write("#define WINRT_IMPL_MODULES\n");
+        if (impl)
+        {
+            w.write("export module winrt:%.%;\n", ns, module_friendly_impl(impl));
+        }
+        else
+        {
+            w.write("export module winrt:%;\n", ns);
+        }
+
+        w.write("import std;\n");
+
+        w.write_import("base");
+        if (!impl)
+        {
+            write_parent_imports(w, c, ns);
+        }
+
+        for (auto&& depends : header_writer.depends)
+        {
+            w.write_import(depends.first, import_impl);
+        }
+
+        if (impl != '0')
+        {
+            w.write("export ");
+            w.write_import(ns, impl ? impl - 1 : '2');
+        }
+
+        w.write_depends(ns, impl);
+
+        w.save_module(impl);
+    }
+
     static void write_namespace_0_h(std::string_view const& ns, cache::namespace_members const& members)
     {
         writer w;
@@ -119,6 +182,8 @@ namespace cppwinrt
         }
 
         w.save_header('0');
+
+        write_namespace_ixx({}, {}, ns, 0, '0');
     }
 
     static void write_namespace_1_h(std::string_view const& ns, cache::namespace_members const& members)
@@ -137,25 +202,29 @@ namespace cppwinrt
         write_preamble(w);
         write_open_file_guard(w, ns, '1');
 
+        w.write("#ifndef WINRT_IMPL_MODULES\n");
         for (auto&& depends : w.depends)
         {
             w.write_depends(depends.first, '0');
         }
 
         w.write_depends(w.type_namespace, '0');
+        w.write("#endif\n");
         w.save_header('1');
+
+        write_namespace_ixx({}, w, ns, '0', '1');
     }
 
     static void write_namespace_2_h(std::string_view const& ns, cache::namespace_members const& members)
     {
         writer w;
         w.type_namespace = ns;
 
-        bool promote;
+        write_structs_result structs_info;
         {
             auto wrap_type = wrap_type_namespace(w, ns);
             w.write_each<write_delegate>(members.delegates);
-            promote = write_structs(w, members.structs);
+            structs_info = write_structs(w, members.structs);
             w.write_each<write_class>(members.classes);
             w.write_each<write_interface_override>(members.classes);
         }
@@ -165,15 +234,19 @@ namespace cppwinrt
         write_preamble(w);
         write_open_file_guard(w, ns, '2');
 
-        char const impl = promote ? '2' : '1';
+        char const impl = structs_info.promote ? '2' : '1';
 
+        w.write("#ifndef WINRT_IMPL_MODULES\n");
         for (auto&& depends : w.depends)
         {
             w.write_depends(depends.first, impl);
         }
 
         w.write_depends(w.type_namespace, '1');
+        w.write("#endif\n");
         w.save_header('2');
+
+        write_namespace_ixx({}, w, ns, impl, '2');
     }
 
     static void write_namespace_h(cache const& c, std::string_view const& ns, cache::namespace_members const& members)
@@ -219,6 +292,7 @@ namespace cppwinrt
         w.swap();
         write_preamble(w);
         write_open_file_guard(w, ns);
+        w.write("#ifndef WINRT_IMPL_MODULES\n");
         write_version_assert(w);
         write_parent_depends(w, c, ns);
 
@@ -228,7 +302,10 @@ namespace cppwinrt
         }
 
         w.write_depends(w.type_namespace, '2');
+        w.write("#endif\n");
         w.save_header();
+
+        write_namespace_ixx(c, w, ns, '2');
     }
 
     static void write_module_g_cpp(std::vector<TypeDef> const& classes)

cppwinrt/main.cpp

@@ -97,6 +97,7 @@ R"(  local               Local ^%WinDir^%\System32\WinMetadata folder
 
         path output_folder = args.value("output", ".");
         create_directories(output_folder / "winrt/impl");
+        create_directories(output_folder / "winrt/ixx");
         settings.output_folder = canonical(output_folder).string();
         settings.output_folder += std::filesystem::path::preferred_separator;
 
@@ -344,9 +345,9 @@ R"(  local               Local ^%WinDir^%\System32\WinMetadata folder
             group.synchronous(args.exists("synchronous"));
             writer ixx;
             write_preamble(ixx);
-            ixx.write("module;\n");
-            ixx.write(strings::base_includes);
-            ixx.write("\nexport module winrt;\n#define WINRT_EXPORT export\n\n");
+            ixx.write("export module winrt;\n");
+            ixx.write("export ");
+            ixx.write_import("base");
 
             for (auto&&[ns, members] : c.namespaces())
             {
@@ -355,7 +356,8 @@ R"(  local               Local ^%WinDir^%\System32\WinMetadata folder
                     continue;
                 }
 
-                ixx.write("#include \"winrt/%.h\"\n", ns);
+                ixx.write("export ");
+                ixx.write_import(ns);
 
                 group.add([&, &ns = ns, &members = members]
                 {
@@ -366,10 +368,14 @@ R"(  local               Local ^%WinDir^%\System32\WinMetadata folder
                 });
             }
 
+            ixx.flush_to_file(settings.output_folder + "winrt/ixx/winrt.ixx");
+
+            write_shared_h();
+
             if (settings.base)
             {
                 write_base_h();
-                ixx.flush_to_file(settings.output_folder + "winrt/winrt.ixx");
+                write_base_ixx();
             }
 
             if (settings.component)