Unable to load appsettings.json files in isolated functions app

[jpoalaska]

Description

I'm running an isolated worker function on .net 9 using the asp.net core integration configuration and I'm trying to get appsettings files to load. When I call builder.Configuration.AddJsonFile(filepath, false) I get an exception:

The configuration file 'appsettings.test.json' was not found and is not optional. The expected physical path was '/tmp/functions\\standby\\wwwroot/appsettings.test.json'.\n at Microsoft.Extensions.Configuration.FileConfigurationProvider.Load(Boolean reload)\n at Microsoft.Extensions.Configuration.ConfigurationManager.AddSource(IConfigurationSource source)\n at Microsoft.Extensions.Configuration.ConfigurationManager.Microsoft.Extensions.Configuration.IConfigurationBuilder.Add(IConfigurationSource source)\n at Program.<Main>$(String[] args)

Did something change from .net 8 to 9 or maybe in the new Microsoft.Azure.Functions.Worker 2.0 package? I don't think I understand what's happening with this /tmp/functions\standby folder.

[jpoalaska]

My workaround for now until I understand what I'm doing wrong

var binDirectory = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location);
builder
    .AddJsonFile(Path.Combine(binDirectory, "appsettings.json")) 
    .AddJsonFile(Path.Combine(binDirectory, $"appsettings.{environment}.json"), false);