C++ Streams support for hstring and IStringable (#1221)

Author: jaigak

cppwinrt/code_writers.h

@@ -3256,6 +3256,7 @@ struct WINRT_IMPL_EMPTY_BASES produce_dispatch_to_overridable<T, D, %>
             w.write(strings::base_deferral);
             w.write(strings::base_coroutine_foundation);
             w.write(strings::base_stringable_format);
+            w.write(strings::base_stringable_streams);
         }
         else if (namespace_name == "Windows.Foundation.Collections")
         {

cppwinrt/cppwinrt.vcxproj

@@ -80,6 +80,7 @@
     <ClInclude Include="..\strings\base_std_hash.h" />
     <ClInclude Include="..\strings\base_string.h" />
     <ClInclude Include="..\strings\base_stringable_format.h" />
+    <ClInclude Include="..\strings\base_stringable_streams.h" />
     <ClInclude Include="..\strings\base_string_input.h" />
     <ClInclude Include="..\strings\base_string_operators.h" />
     <ClInclude Include="..\strings\base_stringable_format_1.h" />

cppwinrt/cppwinrt.vcxproj.filters

@@ -168,6 +168,9 @@
     </ClInclude>
     <ClInclude Include="..\strings\base_stringable_format.h">
       <Filter>strings</Filter>
+    </ClInclude>
+     <ClInclude Include="..\strings\base_stringable_streams.h">
+      <Filter>strings</Filter>
     </ClInclude>
     <ClInclude Include="..\strings\base_xaml_component_connector.h">
       <Filter>strings</Filter>

strings/base_includes.h

@@ -25,6 +25,10 @@
 #include <directxmath.h>
 #endif
 
+#ifndef WINRT_LEAN_AND_MEAN
+#include <ostream>
+#endif
+
 #ifdef __cpp_lib_format
 #include <format>
 #endif

strings/base_string_operators.h

@@ -160,4 +160,12 @@ WINRT_EXPORT namespace winrt
     {
         return impl::concat_hstring(left, right);
     }
+
+#ifndef WINRT_LEAN_AND_MEAN
+    inline std::wostream& operator<<(std::wostream& stream, hstring const& string)
+    {
+        stream << static_cast<std::wstring_view>(string);
+        return stream;
+    }
+#endif
 }

strings/base_stringable_streams.h

@@ -0,0 +1,8 @@
+
+#ifndef WINRT_LEAN_AND_MEAN
+inline std::wostream& operator<<(std::wostream& stream, winrt::Windows::Foundation::IStringable const& stringable)
+{
+    stream << stringable.ToString();
+    return stream;
+}
+#endif

test/old_tests/UnitTests/Tests.vcxproj

@@ -118,6 +118,7 @@
     <ClCompile Include="Reference.cpp" />
     <ClCompile Include="Release.cpp" />
     <ClCompile Include="smart_pointers.cpp" />
+    <ClCompile Include="streams.cpp" />
     <ClCompile Include="struct.cpp" />
     <ClCompile Include="StructCodeGen.cpp" />
     <ClCompile Include="Structures.cpp" />

test/old_tests/UnitTests/Tests.vcxproj.filters

@@ -88,6 +88,7 @@
     <ClCompile Include="conditional_implements_pure.cpp" />
     <ClCompile Include="capture.cpp" />
     <ClCompile Include="com_ref.cpp" />
+    <ClCompile Include="streams.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="catch.hpp" />

test/old_tests/UnitTests/streams.cpp

@@ -0,0 +1,36 @@
+ #include "pch.h"
+#include "catch.hpp"
+#include <sstream>
+
+struct stringable : winrt::implements<stringable, winrt::Windows::Foundation::IStringable>
+{
+    winrt::hstring ToString()
+    {
+        return L"a stringable object";
+    }
+};
+
+TEST_CASE("streams")
+{
+    {
+        std::wstringstream ss;
+        winrt::hstring str = L"Hello World";
+        ss << str;
+        REQUIRE(ss.str() == str);
+    }
+
+    {
+        // Support embedded nulls.
+        std::wstringstream ss;
+        winrt::hstring str = L"Hello\0World";
+        ss << str;
+        REQUIRE(ss.str() == str);
+    }
+
+    {
+        std::wstringstream ss;
+        winrt::Windows::Foundation::IStringable obj = winrt::make<stringable>();
+        ss << obj;
+        REQUIRE(ss.str() == obj.ToString());
+    }
+}