From 18b0d6a72ea2dad4da449fe71f196e126cd408f4 Mon Sep 17 00:00:00 2001
From: Johan Laanstra <jlaans@microsoft.com>
Date: Thu, 9 Sep 2021 17:03:51 -0700
Subject: [PATCH 1/2] Switch to using /await:strict which is binary compatible
 with c++20 coroutines.

---
 nuget/Microsoft.Windows.CppWinRT.targets | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/nuget/Microsoft.Windows.CppWinRT.targets b/nuget/Microsoft.Windows.CppWinRT.targets
index 16d0b020d..989e4a2e0 100644
--- a/nuget/Microsoft.Windows.CppWinRT.targets
+++ b/nuget/Microsoft.Windows.CppWinRT.targets
@@ -871,7 +871,7 @@ $(XamlMetaDataProviderPch)
     <ItemDefinitionGroup>
         <ClCompile>
             <AdditionalOptions>%(AdditionalOptions) /bigobj</AdditionalOptions>
-            <AdditionalOptions Condition="'%(ClCompile.LanguageStandard)' == 'stdcpp17'">%(AdditionalOptions) /await</AdditionalOptions>
+            <AdditionalOptions Condition="'%(ClCompile.LanguageStandard)' == 'stdcpp17'">%(AdditionalOptions) /await:strict</AdditionalOptions>
             <AdditionalIncludeDirectories>%(AdditionalIncludeDirectories);$(GeneratedFilesDir)</AdditionalIncludeDirectories>
         </ClCompile>
         <Midl Condition="'$(CppWinRTModernIDL)' != 'false'">

From 494e571fa4f88e2a14d6b6321e886d0ba740d187 Mon Sep 17 00:00:00 2001
From: Johan Laanstra <jlaans@microsoft.com>
Date: Fri, 10 Sep 2021 07:53:24 -0700
Subject: [PATCH 2/2] Make legacy coroutines opt-in.

---
 nuget/CppWinrtRules.Project.xml          | 5 +++++
 nuget/Microsoft.Windows.CppWinRT.targets | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/nuget/CppWinrtRules.Project.xml b/nuget/CppWinrtRules.Project.xml
index bd0efd57a..7f69fcd74 100644
--- a/nuget/CppWinrtRules.Project.xml
+++ b/nuget/CppWinrtRules.Project.xml
@@ -81,4 +81,9 @@
                 Description="Enables or disables the default for copying binaries to the output folder to be false"
                 Category="General" />
 
+  <BoolProperty Name="CppWinRTEnableLegacyCoroutines"
+                DisplayName="Enable legacy coroutines (C++17)"
+                Description="Enables the /await compiler option (disable this if you want to pass this yourself)"
+                Category="General" />
+
 </Rule>
diff --git a/nuget/Microsoft.Windows.CppWinRT.targets b/nuget/Microsoft.Windows.CppWinRT.targets
index 989e4a2e0..2d00ddc9e 100644
--- a/nuget/Microsoft.Windows.CppWinRT.targets
+++ b/nuget/Microsoft.Windows.CppWinRT.targets
@@ -871,7 +871,7 @@ $(XamlMetaDataProviderPch)
     <ItemDefinitionGroup>
         <ClCompile>
             <AdditionalOptions>%(AdditionalOptions) /bigobj</AdditionalOptions>
-            <AdditionalOptions Condition="'%(ClCompile.LanguageStandard)' == 'stdcpp17'">%(AdditionalOptions) /await:strict</AdditionalOptions>
+            <AdditionalOptions Condition="'%(ClCompile.LanguageStandard)' == 'stdcpp17' And '$(CppWinRTEnableLegacyCoroutines)' != 'false'">%(AdditionalOptions) /await</AdditionalOptions>
             <AdditionalIncludeDirectories>%(AdditionalIncludeDirectories);$(GeneratedFilesDir)</AdditionalIncludeDirectories>
         </ClCompile>
         <Midl Condition="'$(CppWinRTModernIDL)' != 'false'">