Error in handling closed websocket for inline completer

[krassowski]

Description

When websocket gets disconnected we see:

Uncaught TypeError: Cannot read properties of undefined (reading '_reject')
    at reject (jlab_core.0c882064cb12a87cda90.js?v=0c882064cb12a87cda90:1:1731169)
    at we._onClose (392.e7fabd325dafbe2024f7.js?v=e7fabd325dafbe2024f7:1:37258)
    at i.onclose (392.e7fabd325dafbe2024f7.js?v=e7fabd325dafbe2024f7:1:37860)

Reproduce

This comes from:

jupyter-ai/packages/jupyter-ai/src/completions/handler.ts

Lines 113 to 123 in 3bfce32

	private _onClose(e: CloseEvent, reject: any) {
	reject(new Error('Inline completion websocket disconnected'));
	console.error('Inline completion websocket disconnected');
	// only attempt re-connect if there was an abnormal closure
	// WebSocket status codes defined in RFC 6455: https://www.rfc-editor.org/rfc/rfc6455.html#section-7.4.1
	if (e.code === 1006) {
	const delaySeconds = 1;
	console.info(`Will try to reconnect in ${delaySeconds} s.`);
	setTimeout(async () => await this._initialize(), delaySeconds * 1000);
	}
	}

Because the reject delegate is not bound to promise instance here:

jupyter-ai/packages/jupyter-ai/src/completions/handler.ts

Line 140 in 3bfce32

socket.onclose = e => this._onClose(e, promise.reject);

Expected behavior

No error in onClose handling.

Context

• Operating System and version:
• Browser and version:
• JupyterLab version:

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