Add storage account name check to Function App update

azurerm/internal/services/web/resource_arm_function_app.go

@@ -78,7 +78,6 @@ func resourceArmFunctionApp() *schema.Resource {
 			"storage_connection_string": {
 				Type:      schema.TypeString,
 				Required:  true,
-				ForceNew:  true,
 				Sensitive: true,
 			},
 
@@ -429,6 +428,16 @@ func resourceArmFunctionAppUpdate(d *schema.ResourceData, meta interface{}) erro
 		}
 	}
 
+	if d.HasChange("storage_connection_string") {
+		oldValue, newValue := d.GetChange("storage_connection_string")
+		oldAccount := getAccountName(fmt.Sprintf("%s", oldValue))
+		newAccount := getAccountName(fmt.Sprintf("%s", newValue))
+
+		if oldAccount != newAccount {
+			return fmt.Errorf("Error updating storage_connection_string because the AccountName cannot be changed. To change the storage account the resource must be tainted.")
+		}
+	}
+
 	future, err := client.CreateOrUpdate(ctx, resGroup, name, siteEnvelope)
 	if err != nil {
 		return err
@@ -869,3 +878,14 @@ func flattenFunctionAppSiteCredential(input *web.UserProperties) []interface{} {
 
 	return append(results, result)
 }
+
+func getAccountName(storageConnectionString string) string {
+	connectionStringArray := strings.SplitN(storageConnectionString, ";", -1)
+	connectionStringMap := make(map[string]string)
+	for _, pair := range connectionStringArray {
+		z := strings.Split(pair, "=")
+		connectionStringMap[z[0]] = z[1]
+	}
+
+	return connectionStringMap["AccountName"]
+}

website/docs/r/function_app.html.markdown

@@ -95,7 +95,7 @@ The following arguments are supported:
 
 * `app_service_plan_id` - (Required) The ID of the App Service Plan within which to create this Function App.
 
-* `storage_connection_string` - (Required) The connection string of the backend storage account which will be used by this Function App (such as the dashboard, logs).
+* `storage_connection_string` - (Required) The connection string of the backend storage account which will be used by this Function App (such as the dashboard, logs). The access key can be updated, but changing the storage account requires a taint and a recreate to take place.
 
 * `app_settings` - (Optional) A key-value pair of App Settings.