奇怪的AllOf hamcrest匹配器不匹配描述 [英] Strange AllOf hamcrest matcher mismatch description

问题描述

我正在使用 hamcrest 1.3 . matches(Object o, Description mismatch)的实现如下:

I'm using hamcrest 1.3. Its implementation of matches(Object o, Description mismatch) looks like that:

@Override
public boolean matches(Object o, Description mismatch) {
    for (Matcher<? super T> matcher : matchers) {
        if (!matcher.matches(o)) {
            mismatch.appendDescriptionOf(matcher).appendText(" ");
            matcher.describeMismatch(o, mismatch);
          return false;
        }
    }
    return true;
}

在描述不匹配时，它首先附加失败的匹配器的描述，然后才附加实际的不匹配.这样会产生一些非常奇怪的消息.

When describing mismatch, it first appends the description of matcher that failed, and only then the actual mismatch. This results in some pretty odd message.

例如，如果我写:

Description description = new StringDescription();
allOf(lessThan(2)).describeMismatch(5, description);
System.out.println(description.toString());

然后在控制台上打印a value less than <2> <5> was greater than <2>.我希望仅<5> was greater than <2>，因为这是其他匹配器返回的消息，例如lessThan单独使用.

Then a value less than <2> <5> was greater than <2> is printed the console. I would expect just the <5> was greater than <2>, because that's the kind of message the other matchers return, e.g. lessThan used alone.

我的问题是:这是错误还是我错过了什么?

My question being: is this a bug or am I missing something?

不同的匹配器以不同的格式返回消息这一事实非常重要，因为我试图编写一些使用匹配器的自定义验证框架，并且在出现任何问题时能够返回漂亮的人类可读消息.看来我不能为此目的使用describeMismatch方法...

The fact that different matchers return messages in different formats is a big deal, since I was trying to write some custom validation framework that uses the matchers and is able to return nice human readable messages if anything goes wrong. It seems that I can't use the describeMismatch method for that purpose...

推荐答案

我会说这是一个(可用性)错误.仅用单词"but"代替空格即可使消息更具表达力.

I'd say it's a (usability) bug. The message could be more expressive simply with the word "but" instead of the space.

值得指出的是，不匹配消息通常由JUnit的assertThat()显示，并带有其他一些单词:"Expected"(显示Matcher描述)，"Actual"(显示不匹配).这样更清楚了.

It's worth pointing out that the mismatch messages are normally displayed by JUnit's assertThat() with some additional words: "Expected" (shows the Matcher description), "Actual" (shows the mismatch). This makes it clearer.

通常，当您使用allOf()时，您将拥有多个匹配器，因此对于失配描述来说，指出哪个中断是很有用的.但是我同意这个信息可能会更清楚.

Normally when you use an allOf() you'd have more than one matcher, so it's useful for the mismatch description to say which one broke. But I agree the message could be clearer.

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