def optional

bendvy-ecs-core@0.1.0.4 · ordinary_query_declaration.bend:150

import Base
import bendvy-ecs-core@0.1.0.4/column.bend as Col
import bendvy-ecs-core@0.1.0.4/component.bend as Cmp
import bendvy-ecs-core@0.1.0.4/ordinary_declaration.bend as Identity
import bendvy-ecs-core@0.1.0.4/compose.bend as Q
import bendvy-ecs-core@0.1.0.4/capabilities.bend as Cap

150# Grant read access without excluding rows where the component is absent.
151# The body handles Found/ComponentAbsent/MissingEntity; optional fabricates no V.
152# Stale/foreign handles yield MissingEntity and never match as live rows.
153# Payload projection consumes and returns P, preserving affine ownership.
154def optional(~S:Data,~P:Type,~Store:Type,~R:Type,~E:Data,~Rest:Type,~V:Data,~Token:Data,~identity:Identity.Declaration<S,P>,~view:P -> P & V,~take:Store -> Rest & Col.Column<S,P>,~put:Rest -> Col.Column<S,P> -> Store) -> Declaration<S,Q.Frame<S,Store,R,E>,Cap.Read<Q.Frame<S,Store,R,E>,V>>:
155  Declaration{Q.read_family(~S,~Store,~R,~E,~Rest,~P,~V,~Token,~take,~put,~view,~Cmp.Family{Identity.key(~S,~P,identity)}),Q.family_match(~S,~Store,~R,~E,~Rest,~P,~V,~Token,~take,~put,~view,~Cmp.Family{Identity.key(~S,~P,identity)},~Q.Optional{}),[Clause{Identity.key(~S,~P,identity),Optional{}}]}