UUID generation fallback for Node version pre-14.17.0 (#6495)

* UUID generation fallback for Node version pre-14.17.0

* Apply suggestions from code review

* Use module-load-time selection for performance

* Polish

---------

Co-authored-by: Tim te Beek <tim@moderne.io>
Co-authored-by: Knut Wannheden <knut@moderne.io>

Author: 3 people

rewrite-javascript/rewrite/src/uuid.ts

@@ -13,10 +13,34 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {randomUUID} from "crypto";
+import * as crypto from "crypto";
 
 export type UUID = string;
 
-export function randomId(): UUID {
-    return randomUUID();
+/**
+ * Fallback UUID v4 generator for Node versions before 14.17.0
+ */
+function fallbackRandomId(): UUID {
+    const bytes = crypto.randomBytes(16);
+
+    // Set version 4 bits (0100xxxx in byte 6)
+    bytes[6] = (bytes[6] & 0x0f) | 0x40;
+
+    // Set variant bits (10xxxxxx in byte 8)
+    bytes[8] = (bytes[8] & 0x3f) | 0x80;
+
+    // Convert to hex string with dashes
+    const hex = bytes.toString('hex');
+    return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
 }
+
+/**
+ * Generate a random UUID v4.
+ *
+ * Uses native crypto.randomUUID() on Node 14.17.0+, falls back to
+ * crypto.randomBytes() on older versions. The implementation is
+ * selected once at module load time to avoid per-call overhead.
+ */
+export const randomId: () => UUID = typeof crypto.randomUUID === 'function'
+    ? crypto.randomUUID
+    : fallbackRandomId;

rewrite-javascript/rewrite/test/uuid.test.ts

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import {describe} from "@jest/globals";
+import {randomId} from "../src/uuid";
+
+describe("randomId", () => {
+    test("generates valid UUID v4 format", () => {
+        const uuid = randomId();
+        // UUID v4 format: xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
+        // where y is one of 8, 9, a, or b
+        const uuidV4Regex = /^[0-9a-f]{8}-[0-9a-f]{4}-4[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i;
+        expect(uuid).toMatch(uuidV4Regex);
+    });
+
+    test("generates unique IDs on each call", () => {
+        const ids = new Set<string>();
+        const iterations = 1000;
+
+        for (let i = 0; i < iterations; i++) {
+            ids.add(randomId());
+        }
+
+        expect(ids.size).toBe(iterations);
+    });
+
+    test("returns string type", () => {
+        const uuid = randomId();
+        expect(typeof uuid).toBe("string");
+    });
+
+    test("returns 36 character string", () => {
+        const uuid = randomId();
+        expect(uuid.length).toBe(36);
+    });
+});