What-If should understand resources that are managed by other resources declared in the template

[alex-frankel]

Examples:

• VMs will create disks
• AKS will setup a VMSS cluster
• DeploymentScripts will create ACI + Storage

[alex-frankel]

Customer reported examples:

• The what-if output does not include the creation of any VM disks #67

[JustinGrote]

Here's an example I have. I'm attaching VM domain join extensions via a looped reference to another nested deployment. The domain join extensions don't show up at all in whatif. If whatif can't evaluate these it should at least show a warning that it expects additional resources of a certain type to be created.

[alex-frankel]

@JustinGrote I think this is actually in issue with the reference() call. What-if is able to evaluate nested templates, but if there are references() to resolve the name or resourceId of the resources in the nested template, what-if will not find those resources since it doesn't know what to look for.

We have a separate issue (#83) tracking cases related to the reference() function. Can you add this there?

[JustinGrote]

@alex-frankel it may help in the output to note it as "calculated" or maybe have a new whatif status of "Inconclusive" to indicate that ARM doesn't know if this will change or not because it can't evaluate the reference. This is how Terraform handles states like this. It should evalute the reference or at least guess if possible (my example it would be guessable), but I understand that would probably be a large engineering effort with a lot of edge cases.

[alex-frankel]

Yeah, I agree we should provide more information as to what as happening. We will discuss this during our triage this week. cc @shenglol @majastrz

If we implement #83, it should resolve the issue you are hitting

[shenglol]

#46.