Address remaining PR comments

src/lib/util.ts

@@ -19,6 +19,36 @@ export const ucFirst = (s: string) => s.slice(0, 1).toUpperCase() + s.slice(1)
 
 export const errorMessage = (err: unknown) => String(err).replace(/^.*Error: /, "")
 
+export class AbortError extends Error {
+  constructor() {
+    super("Aborted")
+    this.name = "AbortError"
+  }
+}
+
+export class TimeoutError extends Error {
+  constructor(message = "Timed out") {
+    super(message)
+    this.name = "TimeoutError"
+  }
+}
+
+/** Returns a promise that rejects with AbortError when signal aborts. Use with Promise.race. */
+export const whenAborted = (signal?: AbortSignal) => {
+  if (!signal) return new Promise<never>(() => {})
+
+  return new Promise<never>((_, reject) => {
+    const onAborted = () => reject(new AbortError())
+    if (signal.aborted) onAborted()
+    else signal.addEventListener("abort", onAborted, {once: true})
+  })
+}
+
+/** Returns a promise that rejects with TimeoutError after ms. Use with Promise.race. */
+export const whenTimeout = (ms: number, opts: {message?: string} = {}) => {
+  return new Promise<never>((_, reject) => setTimeout(() => reject(new TimeoutError()), ms))
+}
+
 export const buildUrl = (base: string | URL, ...pathname: string[]) => {
   const url = new URL(base)