fix(ci): reject malformed targeted docker group size

scripts/plan-targeted-docker-lane-groups.mjs

@@ -1,4 +1,5 @@
 import { fileURLToPath } from "node:url";
+import { parsePositiveInt } from "./lib/numeric-options.mjs";
 
 const BASELINE_SHARDED_LANES = new Set(["published-upgrade-survivor", "update-migration"]);
 
@@ -13,17 +14,6 @@ function splitTokens(raw) {
   ];
 }
 
-function parsePositiveInt(raw, fallback, label) {
-  const parsed = Number.parseInt(String(raw ?? ""), 10);
-  if (!Number.isFinite(parsed)) {
-    return fallback;
-  }
-  if (parsed < 1) {
-    throw new Error(`${label} must be a positive integer. Got: ${JSON.stringify(raw)}`);
-  }
-  return parsed;
-}
-
 function sanitizeLabel(value) {
   return (
     String(value)
@@ -43,7 +33,7 @@ export function planTargetedDockerLaneGroups({
     throw new Error("docker_lanes is required when planning targeted Docker lane groups.");
   }
 
-  const parsedGroupSize = parsePositiveInt(groupSize, 1, "groupSize");
+  const parsedGroupSize = parsePositiveInt(groupSize, "groupSize");
   const baselineSpecs = splitTokens(upgradeSurvivorBaselines);
   const groups = [];
   let pendingLanes = [];

test/scripts/targeted-docker-lane-groups.test.ts

@@ -65,4 +65,19 @@ describe("scripts/plan-targeted-docker-lane-groups", () => {
       { docker_lanes: "published-upgrade-survivor", label: "published-upgrade-survivor" },
     ]);
   });
+
+  it("rejects malformed group size values", () => {
+    expect(() =>
+      planTargetedDockerLaneGroups({
+        groupSize: "2x",
+        lanes: "doctor-switch update-channel-switch",
+      }),
+    ).toThrow("groupSize must be a positive integer");
+    expect(() =>
+      planTargetedDockerLaneGroups({
+        groupSize: 0,
+        lanes: "doctor-switch update-channel-switch",
+      }),
+    ).toThrow("groupSize must be a positive integer");
+  });
 });