Intl.ListFormat not being returned for Chrome 71 in Xiaomi phone

[Daymannovaes]

The error can be reproduced as the following:

const request = require("request");

function withUserAgent(userAgent) {
    return {
        url: "https://polyfill.app/api/polyfill?features=intl.list-format",
        headers: {
            "User-Agent": userAgent
        }
    };
}

// this is a real user agent from mi browser in a Xiaomi phone
const chrome71xiaomi = "Mozilla/5.0 (Linux; U; Android 10; en-us; SM-G975F Build/QP1A.190711.020) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/71.0.3578.141 Mobile Safari/537.36 XiaoMi/MiuiBrowser/12.1.3-g";

// this is a real user agent from a Pixel 2 XL
const chrome71      = "Mozilla/5.0 (Linux; Android 8.0.0; Pixel 2 XL Build/OPD1.170816.004) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.141 Mobile Safari/537.36";

// This one is just like the above one, but with "XiaoMi/MiuiBrowser/12.1.3-g" added at the end
const chrome71fake  = "Mozilla/5.0 (Linux; Android 8.0.0; Pixel 2 XL Build/OPD1.170816.004) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.141 Mobile Safari/537.36 XiaoMi/MiuiBrowser/12.1.3-g";

request(
    withUserAgent(chrome71xiaomi),
    (error, response, body) => console.log("chrome71xiaomi: ", body.length)
);

request(
    withUserAgent(chrome71),
    (error, response, body) => console.log("chrome71: ", body.length)
);

request(
    withUserAgent(chrome71fake),
    (error, response, body) => console.log("chrome71fake: ", body.length)
);

The resulting log is:

chrome71xiaomi:  0
chrome71fake:  0
chrome71:  15477

Which is obviously an error.

[Daymannovaes]

I just discovered that any polyfill will work in Xiaomi user-agent.

If you request for https://polyfill.app/api/polyfill?features=requestidlecallback, in Chrome 40, the same happens.

const chrome40xiaomi = "Mozilla/5.0 (Linux; U; Android 10; en-us; SM-G975F Build/QP1A.190711.020) AppleWebKit/537.36 (KHTML, like Gecko) Version/4.0 Chrome/40.0.3578.141 Mobile Safari/537.36 XiaoMi/MiuiBrowser/12.1.3-g";
const chrome40       = "Mozilla/5.0 (Linux; Android 8.0.0; Pixel 2 XL Build/OPD1.170816.004) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.3578.141 Mobile Safari/537.36";
const chrome40fake   = "Mozilla/5.0 (Linux; Android 8.0.0; Pixel 2 XL Build/OPD1.170816.004) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/40.0.3578.141 Mobile Safari/537.36 XiaoMi/MiuiBrowser/12.1.3-g";

request(
    withUserAgent(chrome40xiaomi), (_, __, body) => console.log("chrome40xiaomi: ", body.length)
);

request(
    withUserAgent(chrome40), (_, __, body) => console.log("chrome40: ", body.length)
);

request(
    withUserAgent(chrome40fake), (_, __, body) => console.log("chrome40fake: ", body.length)
);

results in

chrome40:  4001
chrome40xiaomi:  0
chrome40fake:  0

[wessberg]

Hey there. Thanks for reporting it. It has been fixed and deployed to production.