Azure Function Isolated Mode. Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions....'. Microsoft.Azure.WebJobs.Host: '%Azure:ServiceBus:Queue%' does not resolve to a value.

[textbytext]

Azure Function Isolated Mode.

Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions....'. Microsoft.Azure.WebJobs.Host: '%KEY:NAME%' does not resolve to a value.

My configuration:

<PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net6.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
</PropertyGroup>
...
<PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.21.0" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.17.2" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.2.0" />        
<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.EventGrid" Version="3.4.1" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.1.0" />
<PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.ServiceBus" Version="5.17.0" />

Usage:

[Function("Function-Name")]
public async Task Run(
    [ServiceBusTrigger(
        queueName: "%Azure:ServiceBus:Queue%",
        Connection = "SERVICEBUS:CONNECTION:STRING")]
    ServiceBusReceivedMessage message,
    ServiceBusMessageActions messageActions,
    CancellationToken cancellationToken)
{
   ...
}

"%Azure:ServiceBus:Queue%" and "SERVICEBUS:CONNECTION:STRING" are taking from an AzureKeyVault (HostBuilder config)

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults()
    .ConfigureHostConfiguration(builder =>
    {
        builder.AddAzureKeyVaultSettingsConfiguration(GetKeyVaultName());
    })
    .ConfigureServices(services =>
    {
        ...
    })
    .Build();

Error:
Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.Function-Name'. Microsoft.Azure.WebJobs.Host: '%Azure:ServiceBus:Queue%' does not resolve to a value.

My assumption:
The problem is in the FunctionIndexProvider.cs file.

FunctionIndexer indexer = new FunctionIndexer(_triggerBindingProvider, 
...
_instanceServicesFactory, 
null, 
_sharedQueue, 
...
_defaultRetryStrategy); 

The INameResolver does not passing (null instead) to the constructor.

[eriktack]

I can only get my function app to read %somevalue% in a queue trigger if it is set as an environment variable after switching to isolated mode. If it is set in appsettings.json its ignored and I get the same error as you get.

It seems like whatever INameResolver is used in Microsoft.Azure.WebJobs.Host.NameResolverExtensions.ResolveWholeStringCore when configuring %%-values is only able to read environment variables.

Note: In the application, if i inject IConfiguration anywhere, it has all values from appsettings.json.