Why is az webapp up detecting my runtime when I have specified it vis --runtime?

I’m trying to create a new webapp using az webapp up and I have specified the runtime with --runtime "PYTHON:3.9", but I get an auto-detect error

Command Name az webapp up

Errors:

Could not auto-detect the runtime stack of your app.
HINT: Are you in the right folder?
For more information, see 'https://go.microsoft.com/fwlink/?linkid=2109470'

To Reproduce:

Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

• az webapp up -n myWebAppName -g myResourceGroupName --runtime "PYTHON:3.9" -l westus3 --logs -p myPlanName --sku B2

Expected Behavior

I expect the command to create the RG, ASP, Web App, and then deploy the app

Environment Summary

Windows-10-10.0.19044-SP0
Python 3.10.3
Installer: MSI

azure-cli 2.35.0

Extensions:
containerapp 0.3.0

Dependencies:
msal 1.17.0
azure-mgmt-resource 20.0.0

Additional Context

[charris-msft]

@StrawnSC - It was just a test I was setting up so I don’t have a repo for it. If I hit it again, I’ll create a repo and share it.

[panchagnula]

@StrawnSC my guess the detection here is because there is on OS & this might be a new app, so wr try to detect language for which default OS to use, but we should honor the --runtime. Can you check if we can make Changes to use --runtime value to set OS as well, in this scenario.