Inspect Bicep what-if diagnostics before treating an omitted resource as unchanged

Source facts

Bicep what-if can short-circuit when a resource identifier, API version, or dependency cannot be evaluated outside deployment. A module can also be excluded, leaving all of its resources out of the analysis; the API returns a diagnostic for that condition.

Microsoft says Az PowerShell 13.1.0 or later and Azure CLI 2.75.0 or later display these diagnostics. Earlier tool versions can encounter the same incomplete analysis without displaying the warning. Microsoft Learn.

Applicability

Identify the tool version, submitted Bicep files, parameters, and expected resource set. Treat what-if as a prediction to inspect, not as proof that every resource was fully analyzed or that deployment is authorized.

DSE recommendation

DSE recommends reviewing diagnostics alongside the proposed resource changes. Reconcile the expected modules and resources with the analyzed output and assign unexplained omissions to the template owner. Preserve the tool version and parameters with the result so reviewers can distinguish a template problem from a client that hides the relevant diagnostic.

Verification

In a controlled example, compare a fully evaluable resource with one affected by an unresolved deployment expression. Confirm the chosen tool exposes the diagnostic and that the review process marks the preview incomplete. Rerun after an approved correction and verify coverage before relying on the predicted changes for a production decision.

Official references

Microsoft Learn: Bicep What-If: Preview Changes Before Deployment. Source retrieved September 9, 2026.