fix: parse a class name even when it has no description

lib/dsn-pcb/dsn-json-to-circuit-json/parse-dsn-to-dsn-json.ts

@@ -860,13 +860,10 @@ function processNet(nodes: ASTNode[]): Net {
 
 function processClass(nodes: ASTNode[]): Class {
   const classObj: Partial<Class> = {}
-  if (
-    nodes[1].type === "Atom" &&
-    typeof nodes[1].value === "string" &&
-    nodes[2].type === "Atom" &&
-    typeof nodes[2].value === "string"
-  ) {
+  if (nodes[1].type === "Atom" && typeof nodes[1].value === "string") {
     classObj.name = nodes[1].value
+  }
+  if (nodes[2]?.type === "Atom" && typeof nodes[2].value === "string") {
     classObj.description = nodes[2].value
   }
 

tests/repros/repro22-class-name-without-description.test.ts

@@ -0,0 +1,43 @@
+import { expect, test } from "bun:test"
+import { parseDsnToDsnJson } from "lib"
+
+/**
+ * Part of https://github.com/tscircuit/dsn-converter/issues/54
+ *
+ * processClass only set `classObj.name` when nodes[1] AND nodes[2] were both
+ * string atoms, treating nodes[2] as a required "description". But a class
+ * with no description (nodes[2] is the first nested list, e.g.
+ * `(clearance_class ...)`, not a string) is valid DSN -- see the `default`
+ * class in tests/assets/testkicadproject/freeroutingTraceAdded.dsn. The
+ * class's name was silently dropped whenever it had no description.
+ */
+test("a class with no description still gets its name parsed", () => {
+  const dsn = `(pcb "test.dsn"
+  (parser
+    (string_quote ")
+    (space_in_quoted_tokens on)
+    (host_cad "test")
+    (host_version "1")
+  )
+  (resolution um 10)
+  (unit um)
+  (structure
+    (layer Top (type signal) (property (index 0)))
+    (boundary (path pcb 0 0 0 0 100 0 100 100 0 100 0 0))
+    (via "")
+    (rule (width 200))
+  )
+  (placement)
+  (library)
+  (network
+    (class default
+      (clearance_class default)
+      (rule (width 200))
+    )
+  )
+  (wiring)
+)`
+
+  const dsnJson = parseDsnToDsnJson(dsn) as any
+  expect(dsnJson.network.classes[0].name).toBe("default")
+})