wx.downloadFile下载文档链接后，临时文件后缀名变json?

预下载文档链接：https://tt.wo.cn/codeshop-web-zsc/api/common/oss/getBiFile?fileId=2020/08/04/7agkdiv2qaijrp6g45qe9l4sih.docx
文档路径：http://tmp/wxd09bd3b7e8615d34.o6zAJs1nxb9ingS3FdkyhKJfJIrw.Yhjzb0wXa7SPae30557a5d8d32ebfe0d43cf6783f695.json

console.log('预下载文档链接：' + file);
      wx.downloadFile({
        url: file,
        success: function (res) {
          const filePath = res.tempFilePath
          console.log('文档路径：' + filePath);
          wx.openDocument({
            filePath: filePath,
            showMenu: true,
            fileType: fileType,
            success: function (rs) {
              console.log('打开文档成功')
            },
            fail: function (r) {
              console.log('打开文档失败')
              console.log(r)
            }, complete: () => {
              wx.hideLoading();
            }
          })
        },
        fail: function () {
          wx.showToast({
            title: '文件下载失败',
            icon: 'none'
          })
        }, complete: () => {
          // wx.hideLoading();
        }
      })