fix: use minimum 6.0.0 System.Text.Json version

[mxschmitt]

This does it like the Azure CLI folks: https://github.com/Azure/azure-sdk-for-net/blob/ff337a1ce38c57f770d28a36198d90ad7be27f80/sdk/digitaltwins/Azure.DigitalTwins.Core/samples/DigitalTwinsClientSample/DigitalTwinsClientSample.csproj#L21

But this most likely will regress #2408 since it reverts #2410, requires testing.

Fixes #2696

[mxschmitt]

@campersau seems like a bug in .NET Azure Functions to me in the way how they bundle their assemblies. (they don't publish a custom System.Text.Json package). Curious about your input here.

[campersau]

The problem is that the AzureFunctionsTools which hosts the local functions does include the System.Text.Json.dll with version 6.0.xx as you can see in %LOCALAPPDATA%\AzureFunctionsTools\Releases\4.55.0\cli_x64. I don't know if the same is true when the function gets actually deployed.

In .NET Framework you can work around that by using <bindingRedirect> and in .NET you can workaround that with this code which tries to load assemblies without doing a version check:

AppDomain.CurrentDomain.AssemblyResolve += CurrentDomain_AssemblyResolve;
private Assembly CurrentDomain_AssemblyResolve(object sender, ResolveEventArgs args)
{
    var name = new AssemblyName(args.Name);
    var dll = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, name.Name + ".dll");
    if (File.Exists(dll))
    {
        return Assembly.LoadFrom(dll);
    }
    return null;
}

E.g. .NET will try to load System.Text.Json = 7.0.0 and fails so the custom CurrentDomain_AssemblyResolve is called and will resolve System.Text.Json = 6.0.0 from the AzureFunctionsTools directory and .NET will just use the returned assembly without additional checks and everything works*.

In my opinion libraries should always try to use the lowest dependency version possible since the users can then "override" it by specifying it explicitly in their project.
E.g. if Playwright requires System.Text.Json >= 6.0.0 and I explicitly include a PackageReference to System.Text.Json = 7.0.0 then Playwright will also use 7.0.0 without any hacks*.

* This of course only works at runtime if there aren't any breaking changes which Playwirght uses.

I am not sure what #2408 was about exactly as there isn't enough information for me to reproduce it, maybe there are other solutions for this too.

[mxschmitt]

Thanks for your great investigation! 💯

I don't know if the same is true when the function gets actually deployed.

From my experiments System.Text.Json was not included in the zip which got uploaded to the Azure Function.

I am not sure what #2408 was about exactly as there isn't enough information for me to reproduce it, maybe there are other solutions for this too.

Yeah for me it also wasn't clear anymore, I made a quick .NET 7 test where it looked good.

I guess I'll merge this for now (which is like a revert of #2410 so it should be fine). Thanks again!