AshIntrospection.Rpc.ValueFormatter (AshIntrospection v0.3.0)

Unified value formatting for RPC input/output.

Traverses composite values recursively, applying field name mappings and type-aware formatting at each level.

The type and constraints parameters provide all context needed - no separate "resource" context is required because each type is self-describing:

For Ash resources: field types come from Ash.Resource.Info.attribute/2
For TypedStructs: field types come from constraints[:fields]
For typed maps: field types come from constraints[:fields]
For unions: member type and constraints come from constraints[:types][member]

Configuration

This module uses a config map for language-specific customization:

%{
  input_field_formatter: :camel_case,
  output_field_formatter: :camel_case,
  field_names_callback: :interop_field_names,  # or :typescript_field_names
  get_original_field_name: fn resource, client_key -> ... end,
  format_field_for_client: fn field_name, resource, formatter -> ... end
}

Key Design Principle

The "parent resource" is never needed because each type is self-describing. When we recurse into a nested value, we pass the field's type and constraints, which contain all the information needed to format that value correctly.

Summary

Types

config()

direction()

Functions

format(value, type, constraints, direction, config \\ %{})

Formats a value based on its type and constraints.

Types

config()

@type config() :: %{
  optional(:input_field_formatter) => atom(),
  optional(:output_field_formatter) => atom(),
  optional(:field_names_callback) => atom(),
  optional(:get_original_field_name) => (module(), String.t() -> atom() | nil),
  optional(:format_field_for_client) => (atom(), module() | nil, atom() ->
                                           String.t())
}

direction()

@type direction() :: :input | :output

Functions

format(value, type, constraints, direction, config \\ %{})

@spec format(term(), atom() | tuple() | nil, keyword(), direction(), config()) ::
  term()

Formats a value based on its type and constraints.

Parameters

value - The value to format
type - The Ash type (e.g., MyApp.EmbeddedResource, Ash.Type.Map, {:array, X})
constraints - Type constraints (e.g., [fields: [...]], [instance_of: Module])
direction - :input (client→internal) or :output (internal→client)
config - Configuration map with formatters and callbacks

Returns

The formatted value with field names converted according to direction.