Puppeteer: Cannot create default querySelector.

The internal query handler has neither querySelector nor a querySelectorAll fallback.

Error message

Cannot create default querySelector.

How this error happens

An internal query handler has neither a query method nor the alternate method from which Puppeteer can build a fallback. An empty custom handler illustrates the missing implementation.

The snippets use the imported Puppeteer class for its static query-handler methods. The fix uses the same import.

import {
    Puppeteer,
} from "puppeteer";

Puppeteer.registerCustomQueryHandler(
    "custom",
    {}
);

Public registration catches an empty object earlier. This is a configuration example, not a promise that the public call emits this exact internal fallback error.

How to fix

Register a handler with at least one usable query function.

Puppeteer.registerCustomQueryHandler(
    "custom",
    {
        queryOne: (root, selector) => {
            return root.querySelector(selector);
        },
    }
);

Things to keep in mind

If a plugin bypasses public validation, remove that integration from the reproduction. There is no supported public API for repairing an internal QueryHandler class.

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