[AVM Module Issue]: Site configuration property (Site.SiteConfig.LinuxFxVersion) for Flex Consumption sites is invalid

[PbALpi7xEX]

Check for previous/existing GitHub issues

• I have checked for previous/existing GitHub issues

Issue Type?

Bug

(Optional) Module Version

0.22.0

(Optional) Correlation Id

No response

Description

We have flex consumption apps and are now hitting this error when trying to move from 0.19.3 to 0.22.0

"ErrorEntity": {
│         "ExtendedCode": "51021",
│         "MessageTemplate": "{0} is invalid.  {1}",
│         "Parameters": [
│           "The following site configuration property (Site.SiteConfig.LinuxFxVersion) for Flex Consumption sites",
│           "Please remove or rename it before retrying."
│         ],
│         "Code": "BadRequest",
│         "Message": "The following site configuration property (Site.SiteConfig.LinuxFxVersion) for Flex Consumption sites is invalid.  Please remove or rename it before retrying."
│       }

Not sure if this relates to or is a regression caused by #218 ?

[PbALpi7xEX]

Consulted GH Copilot on potential workaround, it discovered the following:

Root cause: The avm-res-web-site module unconditionally puts linuxFxVersion in the API body. It gates alwaysOn on function_app_uses_fc1, but forgot to do the same for linuxFxVersion. When application_stack is provided for an FC1 app, the helper computes linuxFxVersion = "NODE|22-lts", which Azure's API rejects with error code 51021.

Adding a conditional in my module call around application stack if using FC1 and setting application stack to null seems to have resolved the issue.

Not sure if the suggestion above from Copilot is the correct fix to apply in the AVM module, but sharing here for reference. Leaving this open for now.

[microsoft-github-policy-service]

Warning

Tagging the AVM Core Team (@Azure/avm-core-team-technical-terraform) due to a module owner or contributor having not responded to this issue within 3 business days. The AVM Core Team will attempt to contact the module owners/contributors directly.

Tip

• To prevent further actions to take effect, the "Status: Response Overdue 🚩" label must be removed, once this issue has been responded to.
• To avoid this rule being (re)triggered, the ""Needs: Triage 🔍" label must be removed as part of the triage process (when the issue is first responded to)!

[microsoft-github-policy-service]

Caution

This issue requires the AVM Core Team's (@Azure/avm-core-team-technical-terraform) immediate attention as it hasn't been responded to within 6 business days.

Tip

• To avoid this rule being (re)triggered, the "Needs: Triage 🔍" and "Status: Response Overdue 🚩" labels must be removed when the issue is first responded to!
• Remove the "Needs: Immediate Attention ‼️" label once the issue has been responded to.