Fix NETStandard library using JSON source gen

src/libraries/System.Text.Json/ref/System.Text.Json.Typeforwards.netcoreapp.cs

@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// The compiler emits a reference to the internal copy of this type in our non-NETCoreApp assembly
+// so we must include a forward to be compatible with libraries compiled against non-NETCoreApp System.Text.Json
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.IsExternalInit))]

src/libraries/System.Text.Json/ref/System.Text.Json.csproj

@@ -9,6 +9,10 @@
     <Compile Include="System.Text.Json.cs" />
   </ItemGroup>
 
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <Compile Include="System.Text.Json.Typeforwards.netcoreapp.cs" />
+  </ItemGroup>
+
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">
     <Compile Include="$(CommonPath)System\Runtime\CompilerServices\IsExternalInit.cs" Link="Common\System\Runtime\CompilerServices\IsExternalInit.cs" />
     <Compile Include="$(CoreLibSharedDir)System\Diagnostics\CodeAnalysis\DynamicallyAccessedMembersAttribute.cs" />

src/libraries/System.Text.Json/src/System.Text.Json.Typeforwards.netcoreapp.cs

@@ -0,0 +1,6 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// The compiler emits a reference to the internal copy of this type in our non-NETCoreApp assembly
+// so we must include a forward to be compatible with libraries compiled against non-NETCoreApp System.Text.Json
+[assembly: System.Runtime.CompilerServices.TypeForwardedTo(typeof(System.Runtime.CompilerServices.IsExternalInit))]

src/libraries/System.Text.Json/src/System.Text.Json.csproj

@@ -314,6 +314,7 @@ System.Text.Json.Nodes.JsonValue</PackageDescription>
     <Compile Include="$(CoreLibSharedDir)System\Diagnostics\CodeAnalysis\UnconditionalSuppressMessageAttribute.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETCoreApp'">
+    <Compile Include="System.Text.Json.Typeforwards.netcoreapp.cs" />
     <Compile Include="System\Text\Json\Serialization\JsonSerializerOptionsUpdateHandler.cs" />
   </ItemGroup>
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETCoreApp'">

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.TestLibrary/System.Text.Json.TestLibrary.Roslyn3.11.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <Import Project="System.Text.Json.TestLibrary.targets" />
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\gen\System.Text.Json.SourceGeneration.Roslyn3.11.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+  </ItemGroup>
+</Project>

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.TestLibrary/System.Text.Json.TestLibrary.Roslyn4.0.csproj

@@ -0,0 +1,8 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <Import Project="System.Text.Json.TestLibrary.targets" />
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\gen\System.Text.Json.SourceGeneration.Roslyn4.0.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+  </ItemGroup>
+</Project>

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.TestLibrary/System.Text.Json.TestLibrary.targets

@@ -0,0 +1,17 @@
+<Project>
+  <PropertyGroup>
+    <TargetFrameworks>netstandard2.0</TargetFrameworks>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\System.Text.Json.csproj" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="TestClasses.cs" />
+  </ItemGroup>
+
+  <Target Name="FixIncrementalCoreCompileWithAnalyzers" BeforeTargets="CoreCompile">
+    <ItemGroup>
+      <CustomAdditionalCompileInputs Include="@(Analyzer)" />
+    </ItemGroup>
+  </Target>
+</Project>

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.TestLibrary/TestClasses.cs

@@ -0,0 +1,17 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Text.Json.Serialization;
+
+namespace System.Text.Json.SourceGeneration.Tests.NETStandard
+{
+    public class MyPoco
+    {
+        public string Value { get; set; }
+    }
+
+    [JsonSerializable(typeof(MyPoco))]
+    public partial class NETStandardSerializerContext : JsonSerializerContext
+    {
+    }
+}

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/NETStandardContextTests.cs

@@ -0,0 +1,31 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text.Json.Serialization;
+using System.Text.Json.Serialization.Metadata;
+using Xunit;
+
+namespace System.Text.Json.SourceGeneration.Tests.NETStandard
+{
+    public class NETStandardContextTests
+    {
+        /// <summary>
+        /// Tests that we can serialize and deserialize a type defined in a NETStandard assembly.
+        /// This tests an issue where we were emitting source-gen logic that caused the compiler
+        /// to emit a reference to an internal definition of IsExternalInit that was missing
+        /// on later versions of .NET (since it was defined by the framework).
+        /// </summary>
+        [Fact]
+        public void RoundTripNETStandardDefinedSourceGenType()
+        {
+            MyPoco expected = new MyPoco() { Value = "Hello from NETStandard type."};
+
+            string json = JsonSerializer.Serialize(expected, NETStandardSerializerContext.Default.MyPoco);
+            MyPoco actual = JsonSerializer.Deserialize(json, NETStandardSerializerContext.Default.MyPoco);
+            Assert.Equal(expected.Value, actual.Value);
+        }
+    }
+}

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Roslyn3.11.Tests.csproj

@@ -4,5 +4,6 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\gen\System.Text.Json.SourceGeneration.Roslyn3.11.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+    <ProjectReference Include="..\System.Text.Json.SourceGeneration.TestLibrary\System.Text.Json.TestLibrary.Roslyn3.11.csproj" />
   </ItemGroup>
 </Project>

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Roslyn4.0.Tests.csproj

@@ -4,5 +4,6 @@
 
   <ItemGroup>
     <ProjectReference Include="..\..\gen\System.Text.Json.SourceGeneration.Roslyn4.0.csproj" OutputItemType="Analyzer" ReferenceOutputAssembly="false" />
+    <ProjectReference Include="..\System.Text.Json.SourceGeneration.TestLibrary\System.Text.Json.TestLibrary.Roslyn4.0.csproj" />
   </ItemGroup>
 </Project>

src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Tests/System.Text.Json.SourceGeneration.Tests.targets

@@ -74,6 +74,7 @@
     <Compile Include="MetadataAndSerializationContextTests.cs" />
     <Compile Include="MetadataContextTests.cs" />
     <Compile Include="MixedModeContextTests.cs" />
+    <Compile Include="NETStandardContextTests.cs" />
     <Compile Include="RealWorldContextTests.cs" />
     <Compile Include="SerializationContextTests.cs" />
     <Compile Include="SerializationLogicTests.cs" />