Changing <TargetFramework> to <TargetFrameowrks> in csproj makes code generator stop running

I have some old net40 code that I need to support, and I've found that I can generate the swagger proxy in net6.0 and then compile it to net40. I have this working using a net40 project that includes the generated .cs file, but of course it would be better to consolidate it to a single project.

Here's what the single project would look like. This project is generating the .cs file, but if I change<TargetFramework> to <TargetFrameworks> -- i.e., add two s characters and no other changes -- then the code generator stops working.

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <TargetFramework>net6.0</TargetFramework>
        <ImplicitUsings>disable</ImplicitUsings>
        <!--<Nullable>disable</Nullable>-->
        <IsPackable>false</IsPackable>
    </PropertyGroup>

    <!--
    The purpose of this project is to run swaggergen to obtain the http proxy code.
    This code is then edited by a build task defined below.
    The edited files are then included in Company.TheOldNet40Product.   
    -->

    <ItemGroup Condition=" '$(TargetFramework)' == 'net6.0' ">
        <OpenApiReference Include="swagger.json" Namespace="Company.Product.HttpApiProxy" ClassName="ProductHttpApiProxy" OutputPath="$(ProjectDir)ProductHttpApiProxy.cs">
            <Options>/AdditionalNamespaceUsages:Company.TheOldNet40Product,Company.TheOldNet40Product.Metadata,Company.Product.Database /GenerateDtoTypes:false</Options>

            <CodeGenerator>NSwagCSharp</CodeGenerator>
        <!--<Options>/GenerateDtoTypes:false</Options>-->
        </OpenApiReference>
    </ItemGroup>

    <ItemGroup>
        <PackageReference Include="Microsoft.SourceLink.AzureRepos.Git" Version="1.0.0" PrivateAssets="All" />
        <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
    </ItemGroup>

    <ItemGroup Condition=" '$(TargetFramework)' == 'net40' ">
        <Reference Include="System.Net" />
        <PackageReference Include="Microsoft.Net.Http" Version="2.2.29" />
        <Reference Include="System.ComponentModel.DataAnnotations" />
        <PackageReference Include=" AsyncBridge" Version="0.3.1" />
    </ItemGroup>

    <ItemGroup Condition=" '$(TargetFramework)' == 'net6.0' ">
        <PackageReference Include="Microsoft.Extensions.ApiDescription.Client" Version="3.0.0">
            <PrivateAssets>all</PrivateAssets>
            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
        </PackageReference>
        <PackageReference Include="NSwag.ApiDescription.Client" Version="13.0.5">
            <PrivateAssets>all</PrivateAssets>
            <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
        </PackageReference>
        <PackageReference Include="System.Runtime" Version="4.3.1" />
    </ItemGroup>

    <ItemGroup>
      <ProjectReference Include="..\Company.Product.Model\Company.Product.Model.csproj" />
      <ProjectReference Include="..\Company.TheOldNet40Product.Model\Company.TheOldNet40Product.Model.csproj" />
    </ItemGroup>

    <UsingTask TaskName="ReplaceFileText" TaskFactory="RoslynCodeTaskFactory" AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll">
        <ParameterGroup>
            <InputFilename ParameterType="System.String" Required="true" />
            <OutputFilename ParameterType="System.String" Required="true" />
            <MatchExpression ParameterType="System.String" Required="true" />
            <ReplacementText ParameterType="System.String" Required="true" />
        </ParameterGroup>
        <Task>
            <Using Namespace="System" />
            <Using Namespace="System.IO" />
            <Using Namespace="System.Text.RegularExpressions" />
            <Code Type="Fragment" Language="cs">
                <![CDATA[  
          File.WriteAllText(
            OutputFilename,
            Regex.Replace(File.ReadAllText(InputFilename), MatchExpression, ReplacementText)
            );
        ]]>
            </Code>
        </Task>
    </UsingTask>

    <Target Name="BeforeBuildStep" BeforeTargets="Build">
        <ReplaceFileText InputFilename="$(ProjectDir)ProductHttpApiProxy.cs" OutputFilename="$(ProjectDir)ProductHttpApiProxy.cs" MatchExpression="IReadOnlyDictionary" ReplacementText="IDictionary" />
    </Target>
</Project>

domaindrivendev / Swashbuckle.AspNetCore

Changing <TargetFramework> to <TargetFrameowrks> in csproj makes code generator stop running #2448