Rules applied to a catalog before it reaches a prompt or a validator.

A transformer is either a module implementing this behaviour paired with its argument, {module, argument}, or a one-argument function. Either way it returns a new catalog. Transformers are registered on an A2UIAgent.CatalogConfig, which applies them in order.

Two are built in:

• component_pruning/1 keeps only the named components;
• function_pruning/1 keeps only the named functions.

The allowlist is read literally: an empty list (or nil) keeps nothing, and a name the catalog does not declare is ignored. To keep everything, apply no transformer. The pruned catalog's schema is rebuilt from what it keeps, so its anyComponent, anyFunction and helper $defs refer only to those entries.

iex> {:ok, catalog} =
...>   A2UICore.Catalog.from_json(%{
...>     "catalogId" => "demo",
...>     "protocolVersion" => "v1.0",
...>     "components" => %{
...>       "Label" => %{"type" => "object", "properties" => %{"text" => %{"type" => "string"}}},
...>       "Badge" => %{"type" => "object", "properties" => %{"count" => %{"type" => "number"}}}
...>     }
...>   })
iex> pruned =
...>   A2UIAgent.CatalogTransformer.apply_all(catalog, [
...>     A2UIAgent.CatalogTransformer.component_pruning(["Label", "Unknown"])
...>   ])
iex> Map.keys(pruned.components)
["Label"]