Diagnosing MissingRequiredParameter Errors in Nested ARM Deployments

Goal

Determine why a nested deployment fails with the MissingRequiredParameter error for parameter location even though the parent template supplies a default value.

Constraints

• The parent template defines location with a default value.
• The nested template references location but declares no default.
• Deployment is executed as a separate deployment resource, not an inline template.

Unresolved Decision

Azure documentation states that defaults are not automatically propagated to nested deployments, yet the exact propagation rules—especially across ARM JSON and Bicep compiled JSON—are unclear.

Specific Questions

1. Does the ARM runtime automatically inherit default values for parameters defined in a parent template when passing them to a nested deployment resource?
2. If not, what is the recommended pattern to ensure a nested deployment receives a default value (e.g., explicit parameter mapping, redeclaring defaults, or using Bicep’s parameter inheritance features)?
3. Are there version‑specific differences in this behavior between the ARM template engine and the Bicep compiler that could explain the failure observed in the current deployment?