经测试，在安卓机，微信版本8.0.16中，传一个错误（不存在）的图片，例如：https://img10.360buyimg.com/evalpic/s230x230_jfs/t1/105296/37/16563/60906/5e7c7a68E86a9ae5c/d8a8682c300642ea.jpg!q80.webp

onerror事件不会执行

export function preLoadImg (url, canvas) {
    return new Promise((resolve, reject) => {
            if (canvas) {
                const img = canvas.createImage();
                img.src = url.replace(/\.webp/, '');
                img.onload = () => resolve(img);
                img.onerror = () => reject(img)
                
                return;
            }
            wx.downloadFile({
                url,
                success: res => resolve(res.tempFilePath),
                fail: reject,
            });
            return;
    });
}