Core Tools version: 3.0.3233
Function Runtime Version: 3.0.15193.0

Repro steps

1. Fetch function app configuration from Azure function in azure portal which has AZURE_FUNCTIONS_ENVIRONMENT set
2. Start Azure function locally via Rider run

Expected behavior

Azure function should start up normally and read the AZURE_FUNCTIONS_ENVIRONMENT variable from previously fetched local.settings.json

Actual behavior

Function does not start locally, as the fails to add the AZURE_FUNCTIONS_ENVIRONMENT variable again.

"An item with the same key has already been added. Key: AZURE_FUNCTIONS_ENVIRONMENT"

Known workarounds

Workarund is to remove the AZURE_FUNCTIONS_ENVIRONMENT variable from local.settings.json after fetching the settings from the portal to continue developing it locally.

Related information

Using Rider 2020.3.2 and developing in C#/dotnet

AZURE_FUNCTIONS_ENVIRONMENT should work as any other env variable in my opinion. When it's set in a system/user level, it should get it from there, if not, grab it from local.settings.json. Or at least, it should not stop the function from starting.

I am wondering that this problem isn't more common, as I suspect everyone has set AZURE_FUNCTIONS_ENVIRONMENT in his azure function appsettings in Azure(?) and at least a few use the fetch app settings method to generate local.settings.json to work locally

Maybe I am doing something wrong, please let me know