Use placeholder for missing Rule ID in YAML export file names

src/components/Controls/ExportRulesYAML.tsx

@@ -5,6 +5,7 @@ import { saveAs } from "file-saver";
 import { ColumnOption } from "csv-stringify/browser/esm/sync";
 import { MenuItem } from "@mui/material";
 import JSZip from "jszip";
+import { ruleFileName } from "../../utils/ruleFileName";
 
 const columns: ColumnOption[] = [
   {
@@ -21,9 +22,6 @@ const columns: ColumnOption[] = [
   },
 ];
 
-const cast = (value) =>
-  Array.isArray(value) ? value.join(",") : JSON.stringify(value);
-
 export default function ExportRulesYAML({ onClose }) {
   const { dataService, orderBy, order, searchText, setAlertState } = useContext(
     AppContext
@@ -70,9 +68,10 @@ export default function ExportRulesYAML({ onClose }) {
     const zip = new JSZip();
     for (const rule of rules) {
       zip.file(
-        `${cast(
-          rule["json.Authorities.Standards.References.Rule Identifier.Id"]
-        )}.${rule["id"]}.yml`,
+        ruleFileName(
+          rule["json.Authorities.Standards.References.Rule Identifier.Id"],
+          rule["id"]
+        ),
         rule["content"]
       );
     }

src/utils/ruleFileName.test.ts

@@ -0,0 +1,26 @@
+import { MISSING_RULE_ID, ruleFileName } from "./ruleFileName";
+
+describe("ruleFileName", () => {
+  const id = "3f2a9c1e-7b4d-4c1a-9e2f-0a1b2c3d4e5f";
+
+  it("uses the rule identifier as the file name prefix", () => {
+    expect(ruleFileName(["CORE-000001"], id)).toBe(`CORE-000001.${id}.yml`);
+  });
+
+  it("joins multiple rule identifiers with a comma", () => {
+    expect(ruleFileName(["CORE-000001", "CORE-000002"], id)).toBe(
+      `CORE-000001,CORE-000002.${id}.yml`
+    );
+  });
+
+  it.each([
+    ["an empty array", []],
+    ["an array of empty values", [""]],
+    ["undefined", undefined],
+  ])("uses a placeholder when the rule identifier is %s", (_, ruleId) => {
+    const fileName = ruleFileName(ruleId, id);
+
+    expect(fileName).toBe(`${MISSING_RULE_ID}.${id}.yml`);
+    expect(fileName.startsWith(".")).toBe(false);
+  });
+});

src/utils/ruleFileName.ts

@@ -0,0 +1,16 @@
+/**
+ * Placeholder used when a rule has no Rule Identifier.
+ *
+ * Without it, the exported file name would start with "." (e.g. ".<uuid>.yml"),
+ * which macOS treats as a hidden file.
+ */
+export const MISSING_RULE_ID = "NO_RULE_ID";
+
+const toFileNamePart = (value: unknown): string =>
+  (Array.isArray(value) ? value.join(",") : JSON.stringify(value)) ?? "";
+
+/**
+ * Builds the file name for a rule exported as YAML: `<RuleID>.<id>.yml`.
+ */
+export const ruleFileName = (ruleId: unknown, id: string): string =>
+  `${toFileNamePart(ruleId) || MISSING_RULE_ID}.${id}.yml`;