Set host.json options via .env

I'm a fan of monorepos and my current goto for managing them is NX. I also use Azure Functions regularly. NX makes it easy to use a .env file to manage environment variables, but Azure Functions uses a host.json file to manage settings. I wanted to be able to manage these settings via environment variables as well. Here's how I did it.

Let's say you want to change the loglevel when you're running locally.

In your host.json file, you would have something like this:

{
  "logging": {
    "logLevel": {
      "default": "Debug"
    }
  }
}

But I don't want to change my host.json file for local development. I want it to just contain my production values. I found a post from Derek Hassan where he demontrates how to do set host.json values via the local.settings.json file. These values are just setting environment variables as well, so I just extended the concept to the .env file.

AzureFunctionsJobHost__logging__logLevel__default="Debug"

Now you can easily manage your host.json settings via your .env file but not mess with the host.json file itself!