先添加类

:row-class-name="getRowClass"

 

写个方法

    getRowClass(row, rowIndex) {
      let data = row.row;
      let res = [];
      if (data.realyTask && data.realyTask.length > 0) {
        res.push('row-expand-has')
        return res;
      } else {
        res.push('row-expand-unhas')
        return res;
      }
    },

最后css

>>>.row-expand-unhas .el-icon-arrow-right{
  // pointer-events: none;
  opacity: 0;
}