design.has_netclass

What it is ¶

design.has_netclass(present) yields exactly one row, with the value true, when the design assigns net classes at all, and zero rows otherwise. Like design.has_nc_channel and design.types_power_out it is a design-level flag rather than a per-entity relation, so there is never more than one row, and its presence or absence is the whole signal. The row appears for a KiCad project whose net_settings declares classes. An EDIF netlist, an IPC-2581 board, a bare .kicad_sch read without its project, and a project that declares no classes all produce no row.

For hardware engineers ¶

Net classes only exist if someone set them up in the project. This flag says whether that happened. It matters because a review question scoped to a class (“every HV net must clear 2mm”) has nothing to examine on a design with no classes, and “nothing to examine” is not the same answer as “everything passed”. With the flag, the report can say the check did not apply, instead of quietly counting a pass that nothing examined.

For software engineers ¶

It is a capability probe over the whole design, closer to a feature flag than a row set. Because a rule reads it as design.has_netclass(?_), an absent row makes the enclosing conjunction yield nothing, so a guarded query fails closed rather than returning a confident empty result.

It tells apart two empty results that look identical in the tuples, “no net is in class HV” and “this design has no classes”. The first is a real answer, the second is an unanswerable question, and only the marker separates them.

Go projector ¶

hasNetClassFacts in stdlib/relations/facts.go calls Model.HasNetClasses(), which is true when any net carries a non-empty NetClass. When true the projector returns a single row (subject true); when false it returns nil, so the relation is one row or none, never more. The underlying flag is collected once in the model’s nets walk, alongside the no-connect channel, so the read is O(1).

It is the queryable twin of check.CapNetClass. A Go or Spec rule declares that capability, and check.Available then gates the rule to not-applicable. A datalog query reads this relation for the same signal. The Spec-rule fact design.has_netclass is the third face of it. It is deliberately content-derived rather than format-derived, unlike design.types_power_out. To a class-scoped rule, a KiCad project that declares no classes is in the same position as an EDIF netlist that cannot declare any.

Datalog ¶

Probe the flag directly (one row true, or empty):

design.has_netclass(?present) => ?present

Guard a class-scoped question with it, so the query returns nothing on a design that cannot answer it rather than an empty result that reads like a clean bill of health:

design.has_netclass(?_), net.netclass(?net, "HV"), component.net(?ref, ?net) => ?ref, ?net