Function dependency_order 

pub fn dependency_order(
    template_body: &str,
    parameters: &BTreeMap<String, String>,
    resource_defs: &[ResourceDefinition],
) -> Vec<usize>

Compute a provisioning order for resource_defs such that every resource is provisioned after the resources it references — via an explicit DependsOn or an implicit Ref / Fn::GetAtt / Fn::Sub to another resource’s logical id.

Returns a permutation of indices into resource_defs. CloudFormation provisions in dependency order; FakeCloud previously provisioned in template order, so a Ref to a not-yet-created resource resolved to the bare logical id (the “not yet provisioned” fallback in resolve_refs_full) and got baked into derived state — e.g. a Step Functions ASL whose DefinitionSubstitutions reference a Lambda declared later in the template, leaving the logical id in the definition and failing every invoke with Lambda.ResourceNotFoundException.

The graph is built from the post-ForEach/post-SAM template so the logical ids and reference shapes match what provisioning actually sees. Falls back to the original order on a parse failure or a dependency cycle (which real CFN rejects outright), and breaks ties by original index so the order is deterministic.