[New Feature Request] appsettings.json should have syntax support to enable usage of placeholders for Environment Variables (or any other setting from same config)

[manoj-choudhari-git]

I realized this while working on a code where I had to add transformations on very complex JSON object. The transformation required were very simple.

For ex. I just wanted environment name to be present in a setting.

The issue was that setting was not at top level... there was an array at top level and inside one of the object, there was another array and I wanted to replace the placeholder for only one entry in this nested array.

In appsettings.json transformation files, there is no support yet to have a placeholder. The value of placehoder can come either from same appsettings.json file or it can come from some environment variable.

For ex. if my appsettings.json is as shown below:

{
     "AppSettings": {
            "ApplicationName": "MyWebApp"
      },
     "SomeDependentSetting": "Current environment is {env::ASPNETCORE_ENVIRONMENT}",
      "AnotherSetting": "Current Application is {config::AppSettings:ApplicationName}"
}

This feature would really make configuration transformations easy.

[kalaskarsanket]

This issue was moved to dotnet/aspnetcore#28651