Diffo.Provider.Extension.InheritedPlaceDeclaration (Diffo v0.8.0)

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DSL entity for an inherited_place declaration inside places do on an Instance resource.

Generates an Ash calculation of the same name as role that walks the instance graph to inherit a place from a reached instance. The calculation is injected by TransformInheritedRefs at compile time — no PlaceRef edge is created on the consuming instance itself.

Fields

  • role — atom; the name of the generated calculation (and the place slot name from the consumer's perspective — the surfaced PlaceRef carries this role).
  • source_role — atom; the PlaceRef role to read on each reached instance (e.g. :location). Required. This terminal deref is not a via: hop — via: reaches the instance; routing through a place (the ref graph) is calc territory (see #227).
  • via — the hop chain to the instance holding the ref, in the unified #213 grammar (shared with inherited_characteristic): a bare atom is {:reverse, assignment: alias} shorthand; tuples are {:forward | :reverse, assignment: alias} or {:forward | :reverse, relationship: type | [type: t, alias: a]}. When nil, defaults to [role]. See Diffo.Provider.Extension.Traversal.
  • collapse — :first or :last; collapses the consumer-ordered result list (the refs at source_role across reached instances) to that end. When set, the calc returns a single place or nil rather than a list.

Example

places do
  inherited_place :installation_site, source_role: :location
  inherited_place :exchange, via: [:primary, :uplink], source_role: :location
  # forward relationship hop + collapse to the single reached place
  inherited_place :poi,
    via: [{:forward, relationship: [alias: :circuit]}, {:reverse, assignment: :cvlan}],
    source_role: :locates,
    collapse: :first
end