netclass.via_drill

What it is ¶

netclass.via_drill(class, mm) yields the the via drill diameter a net class DECLARES its nets should route at, in millimetres, one row per class that states one. A class that states no the via drill diameter yields no row, which is a meaningful fact rather than a gap: that field then cascades to a lower-priority class.

This is the DECLARED side. board.via_drill(net, mm) is the ACTUAL side, in the same units, so the two join without conversion. That pairing is the point of the relation.

For hardware engineers ¶

This is the number you typed into Board Setup for that class, read back. Query it to confirm the engine sees the constraints you set, and to check the project against itself: the declared width is what you intended, the routed width is what happened, and a review that compares them contains no number the tool invented.

For software engineers ¶

Keyed by CLASS, not by net, and it is NOT what a rule should compare against. A net can be in several classes, so joining net.netclass to this relation fans out and compares the net’s copper against EVERY class it belongs to. A net correctly routed at its winning class’s width will then “fail” against a losing class’s. Join net.declared_via_drill(net, mm) instead, which resolves the cascade first. This relation exists for introspection and for authoring, not for comparison.

Go projector ¶

netClassDefFacts in stdlib/relations/facts.go walks Model.NetClassDefs(), the ir.Constraint nodes of kind netclass, and parses the via_drill param. Populated in the I/O layer by kicad.AnnotateNetClassDefs from the sibling .kicad_pro net_settings.classes[] (WS3-111).

Absence is not a pass ¶

Only a KiCad project read populates this. An EDIF netlist, an IPC-2581 board, a bare .kicad_sch, and a KiCad project that defines no classes all leave it empty, and a rule scoped by it would find nothing and read clean. has_netclass_defs is the marker that separates those cases, and it is deliberately distinct from has_netclass: membership and definitions are independent blocks of net_settings, so a project can assign nets to a class it never defined.

Datalog ¶

Every class and its declared width:

netclass.via_drill(?class, ?mm) => ?class, ?mm