I am trying to link an existing Azure function to a static web app using Terraform and FastAPI. Provisioning and deployment in devops works fine, but the URL is not working properly.

When I request the function app URL https://func-***.azurewebsites.net/api/v1/ping, I get the following error:

{"code":400,"message":"Login not supported for provider azureStaticWebApps"}

When I request the API path in the static web app URL https://***.azurestaticapps.net/api/v1/ping, I get a 404 Not Found.

I am not sure how to debug this, running the function locally works fine.

This is my Terraform code:

// Create a linux function app
resource "azurerm_linux_function_app" "this" {
  name                       = "func-${var.organization}-${var.application}-${var.environment}"
  location                   = azurerm_resource_group.this.location
  resource_group_name        = azurerm_resource_group.this.name
  service_plan_id            = azurerm_service_plan.this.id
  storage_account_name       = azurerm_storage_account.function.name
  storage_account_access_key = azurerm_storage_account.function.primary_access_key

  identity {
    type = "SystemAssigned"
  }

  site_config {
    always_on                = true
    application_insights_key = azurerm_application_insights.this.instrumentation_key
    application_stack {
      python_version = "3.11"
    }
  }

  app_settings = {
    "SCM_DO_BUILD_DURING_DEPLOYMENT" = "true"
    "URL_BASE"                       = "https://${azurerm_static_web_app.this.default_host_name}"
    "URL_BASE_API"                   = "https://${azurerm_static_web_app.this.default_host_name}/api"
  }

  tags = local.tags

  lifecycle {
    ignore_changes = [auth_settings_v2]
  }
}

// Create static web app
resource "azurerm_static_web_app" "this" {
  name                = "app-${var.organization}-${var.application}-${var.environment}"
  resource_group_name = azurerm_resource_group.this.name
  location            = azurerm_resource_group.this.location
  sku_tier            = "Standard"
  sku_size            = "Standard"
}


// Register the function as API to the static web app
resource "azurerm_static_web_app_function_app_registration" "this" {
  static_web_app_id = azurerm_static_web_app.this.id
  function_app_id   = azurerm_linux_function_app.this.id
}

This is my function code:

import azure.functions as func
import fastapi

fastapi_app = fastapi.FastAPI(root_path="/api/v1")


@fastapi_app.get("/ping")
async def index():
    return "pong"


app = func.AsgiFunctionApp(
    app=fastapi_app, 
    http_auth_level=func.AuthLevel.ANONYMOUS
)

The routePrefix in my host.json is an empty string. Any ideas on how to solve this?