chore: import upstream snapshot with attribution

apps/webapp/test/reloadingRegistry.test.ts

@@ -0,0 +1,79 @@
+import { describe, it, expect } from "vitest";
+import { createReloadingRegistry } from "~/utils/reloadingRegistry.server";
+
+describe("createReloadingRegistry", () => {
+  it("current() is undefined before load, snapshot after isReady", async () => {
+    const reg = createReloadingRegistry({
+      name: "test-a",
+      intervalMs: 10_000,
+      load: async () => ({ value: 42 }),
+    });
+    expect(reg.current()).toBeUndefined();
+    await reg.isReady;
+    expect(reg.isLoaded).toBe(true);
+    expect(reg.current()).toEqual({ value: 42 });
+    reg.stop();
+  });
+
+  it("reload() picks up a changed value", async () => {
+    let v = 1;
+    const reg = createReloadingRegistry({
+      name: "test-d",
+      intervalMs: 10_000,
+      load: async () => v,
+    });
+    await reg.isReady;
+    expect(reg.current()).toBe(1);
+    v = 2;
+    await reg.reload();
+    expect(reg.current()).toBe(2);
+    reg.stop();
+  });
+
+  it("newer load wins even if an older load resolves later", async () => {
+    // load hands the test a deferred resolver per call so completion order is controllable.
+    const deferred: Array<(value: number) => void> = [];
+    const reg = createReloadingRegistry({
+      name: "test-e",
+      intervalMs: 10_000,
+      load: () =>
+        new Promise<number>((resolve) => {
+          deferred.push(resolve);
+        }),
+    });
+
+    // deferred[0] is the startup load; let it complete with an initial value.
+    deferred[0](0);
+    await reg.isReady;
+
+    // start two overlapping loads; don't await yet (deferred[1] older, deferred[2] newer)
+    const older = reg.reload();
+    const newer = reg.reload();
+
+    // resolve the NEWER load first, then the OLDER load last
+    deferred[2](2);
+    deferred[1](1);
+    await Promise.all([older, newer]);
+
+    // the older load completing last must NOT clobber the newer snapshot
+    expect(reg.current()).toBe(2);
+    reg.stop();
+  });
+
+  it("autoStart:false stays inert (never loads)", async () => {
+    let loadCalls = 0;
+    const reg = createReloadingRegistry({
+      name: "test-inert",
+      intervalMs: 10_000,
+      autoStart: false,
+      load: async () => {
+        loadCalls++;
+        return 1;
+      },
+    });
+    expect(reg.isLoaded).toBe(false);
+    expect(reg.current()).toBeUndefined();
+    expect(loadCalls).toBe(0); // never hit the DB/load
+    reg.stop();
+  });
+});