element 自定义form表单校验规则导致validate不执行

1.错误代码

下面的代码看起来似乎是没什么问题，控制台与编译器都没有报错，可是validate就是不执行。

data() {
    var checkSignatoryLength = (rule, value, callback) => {
      if (this.form.signatory !== undefined && this.form.signatory !== null) {
        if (this.form.signatory.length < 2) {
          return callback(new Error('需至少选择两个签字人'));
        } 
      }
    };
    return {
    	rules{
          signatory: [
            { required: true, message: '请选择签字人', trigger: 'change' },
            { required: true, validator: checkSignatoryLength, trigger: 'change' }
          ]
	}
    }
}

2.解决办法

校验代码添加else返回callback();

data() {
    var checkSignatoryLength = (rule, value, callback) => {
      if (this.form.signatory !== undefined && this.form.signatory !== null) {
        if (this.form.signatory.length < 2) {
          return callback(new Error('需至少选择两个签字人'));
        } else {
          callback();
        }
      }
    };
    return {
    	rules{
          signatory: [
            { required: true, message: '请选择签字人', trigger: 'change' },
            { required: true, validator: checkSignatoryLength, trigger: 'change' }
          ]
	}
    }
}

3.原因

自定义校验规则无论校验是否通过都一定要返回callback()