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Type the verifyClient callback in the ws library definition #2225

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javache merged 1 commit into from
Nov 13, 2026
+7 −1
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Type the verifyClient callback in the ws library definition #2225

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8 changes: 7 additions & 1 deletion flow-typed/npm/ws_v7.x.x.js
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Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,13 @@ declare class ws$WebSocketServer extends events$EventEmitter {
perMessageDeflate?: boolean | ws$PerMessageDeflateOptions,
port?: number,
server?: http$Server | https$Server,
verifyClient?: () => unknown,
verifyClient?: (
info: Readonly<{
origin: string,

@github-actions github-actions Bot Nov 13, 2026

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should fix · origin is typed as string, but ws passes undefined when the client sends no Origin header

ws 7.x builds the info object as origin: req.headers[version === 8 ? 'sec-websocket-origin' : 'origin'] (ws/lib/websocket-server.js:252-257). Browsers always send that header. Node clients, CLI tools, native apps and many proxies often don't, and then info.origin is undefined.

With this libdef, verifyClient: info => info.origin.startsWith('http://localhost') type-checks, but it throws a TypeError inside the server's upgrade handling when such a client connects. The stated motivation is callers that read origin, and an origin allowlist is exactly where a missing-header case matters, so the type should make callers handle it.

Suggested fix: origin?: string (or origin: string | void). React Native's copy of this definition should get the same change.

Optional, since the old () => unknown type also rejected it: ws also supports an async form, (info, cb) => void, selected by verifyClient.length === 2. The new type still rejects it with "requires another argument". If you want it covered, add an optional callback?: (verified: boolean, code?: number, message?: string, headers?: {[string]: string}) => void parameter.

Reproduced: repro/origin-repro.js starts a ws 7.5.10 server with a verifyClient that logs info.origin, then connects with the Node ws client. It prints origin: undefined undefined. repro/__review_verifyClient.js, placed temporarily in packages/metro/src/lib, used info.origin.startsWith(...) and Flow accepted it with no error. The same file's two-argument (info, cb) form failed with incompatible-type, "requires another argument". · id 487658c6

secure: boolean,
req: http$IncomingMessage<>,
}>,
) => unknown,
},
callback?: () => unknown,
): this;
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