fix(pad): default w and h to 1mm so a bare pad renders (#788)

src/fn/pad.ts

@@ -6,16 +6,20 @@ import { length } from "circuit-json"
 import { mm } from "@tscircuit/mm"
 import { base_def } from "../helpers/zod/base_def"
 
+// Default to a 1mm square pad (the same fallback smtpad uses) so a bare `pad`
+// name renders instead of throwing a raw TypeError from mm(undefined). Pass w
+// and h to size the pad for a specific part.
 export const pad_def = base_def.extend({
-  w: length,
-  h: length,
+  w: length.default("1mm").describe("width of the pad"),
+  h: length.default("1mm").describe("height of the pad"),
 })
 
 export type PadDef = z.input<typeof pad_def>
 
 export const pad = (
-  params: PadDef,
-): { circuitJson: AnySoupElement[]; parameters: PadDef } => {
+  rawParams: PadDef,
+): { circuitJson: AnySoupElement[]; parameters: any } => {
+  const params = pad_def.parse(rawParams)
   const { w, h } = params
   const width = mm(w)
   const height = mm(h)

tests/pad_bare.test.ts

@@ -0,0 +1,15 @@
+import { test, expect } from "bun:test"
+import { convertCircuitJsonToPcbSvg } from "circuit-to-svg"
+import { fp } from "../src/footprinter"
+
+test("pad renders from a bare name", () => {
+  // `pad` is advertised by getFootprintNames(); a bare `pad` used to throw a raw
+  // TypeError from mm(undefined) for the missing w and h. It now defaults to a
+  // 1mm square pad, the same fallback smtpad uses, so the name renders.
+  const soup = fp.string("pad").circuitJson()
+  const pads = soup.filter((e) => e.type === "pcb_smtpad")
+  expect(pads.length).toBe(1)
+  expect(pads[0]).toMatchObject({ width: 1, height: 1, x: 0, y: 0 })
+  const svgContent = convertCircuitJsonToPcbSvg(soup)
+  expect(svgContent).toMatchSvgSnapshot(import.meta.path, "pad_bare")
+})