V4 Azure function Timer Trigger configuration in AppSettings does not work in .NET 7

Question

var host = new HostBuilder()
.ConfigureAppConfiguration((host, builder) =>
{
    builder
        .AddJsonFile("appsettings.json", true, true)
        .AddJsonFile($"appsettings.{host.HostingEnvironment.EnvironmentName}.json", true, true);
}).Build().Run();

Above is a portion of the code in my V4 Azure Function's Program.cs which runs on .NET 7.0

In my Azure Function, I use the %configurationName% convention to trigger this timer function every minute.

    [Function(nameof(FunctionATrigger))]
    public async Task Run(
        [TimerTrigger("%Values:TimerTriggerPeriod%", RunOnStartup = false)] TimerInfo timerInfo)
    {
    }

However, I keep getting the error:

[2023-03-16T17:44:37.042Z] The 'FunctionATrigger' function is in error: Microsoft.Azure.WebJobs.Host: Error indexing method 'Functions.FunctionATrigger'. Microsoft.Azure.WebJobs.Host: '%Values:TimerTriggerPeriod%' does not resolve to a value.

I confirmed my host.HostingEnvironment.EnvironmentName is 'local'

In my appsettings.local.json I have:

{
   "Values": {
      "TimerTriggerPeriod": "0 * * * * *"
   }
}

I also tried %TimerTriggerPeriod% with the following appsetting without sucess :

{
   "TimerTriggerPeriod": "0 * * * * *"
}

Could this be something in .NET 7 and Azure Function V4?

As a test I verified I can access this value via Dependency Injection of IConfiguration

_configuration["Values:TimerTriggerPeriod"]

Answer 1

Make sure you are loading appsettings.local.json. In order to verify you can add the config section to your secrets file or add them to appsettings.json.The following works for me:

[Function(nameof(FunctionATrigger))]
public async Task Run(
    [TimerTrigger("%MyFunctionName:DailyCronMidnightPST%"
    #if !RELEASE
        , RunOnStartup = true
    #endif
    )] TimerInfo myTimer, ILogger log)
{
}

appsettings.local.json:

{
    "MyFunctionName": {
        "4HourCronStartAt1AMPST": "0 0 8/4 * * *",
        "DailyCronMidnightPST": "0 0 7 * * *",
        "Throughput": 10000,
        "BatchSize": 100
    }
}