FunctionsPreservedDependencies doesn't preserve files

[NickSevens]

I'm building an Azure Function app and have an issue where it fails to load System.IdentityModel.Tokens.Jwt.dll.

It seems the dll is removed due to the assembly cleaning process, which I can disable using <_FunctionsSkipCleanOutput>true</_FunctionsSkipCleanOutput> (this works as described)

However I read at https://docs.microsoft.com/en-us/azure/azure-functions/functions-develop-vs#configure-your-build-output-settings I could preserve a single dll using:

<ItemGroup>
    <FunctionsPreservedDependencies Include="System.IdentityModel.Tokens.Jwt.dll" />
</ItemGroup>

This doesn't seem to preserve the DLL however. I can see in the \bin\Debug\netcoreapp3.1\bin the DLL is indeed not available. It is available when _FunctionsSkipCleanOutput was used.

Environment:

Tool	Version
Visual Studio Enterprise	16.8.4
Azure Functions and Web Jobs Tools	16.8.557.25636 (not sure if this is relevant?)
Azure Functions Core Tools	3.0.3284 (not sure if this is relevant?)
Azure Functions Runtime Version	3.0.15371.0 (not sure if this is relevant?)

[fowl2]

Support for FunctionsPreservedDependencies was added in Microsoft.Azure.WebJobs.Script.ExtensionsMetadataGenerator 1.2.1, which was first included in Microsoft.NET.Sdk.Functions version 3.0.12, so check that you're using at least that version.