如何将参数传递给@Provide？

Question

有没有办法把参数传递给@Provide？我想要的东西相当于以下内容：

@Property
void test(@ForAll("charSequence", 2, 5) CharSequence cs) {
    // test property on cs, which is an arbitrary CharSequence of length minimum 2 and maximum length 5
}

@Provide
Arbitrary<CharSequence> charSequence(int minLength, int maxLength) {
    Arbitrary<String> stringArbitrary = Arbitraries.strings().ofMinLength(minLength).ofMaxLength(maxLength).injectNull(0.01);
    Arbitrary<StringBuffer> stringBufferArbitrary = stringArbitrary.map
        (str -> null == str ? null : new StringBuffer(str));
    Arbitrary<StringBuilder> stringBuilderArbitrary = stringArbitrary.map
        (str -> null == str ? null : new StringBuilder(str));
    return Arbitraries.oneOf(stringArbitrary, stringBufferArbitrary, stringBuilderArbitrary);
}

我尝试创建自定义注释

public @interface Length {
    int min();
    int max();
}

并按照Provider Methods with Parameters中的建议将其用作void test(@ForAll("charSequence") @Length(min = 2, max = 5) CharSequence cs)，但TypeUsage似乎没有采用自定义批注@Length。(仅拾取@ForAll。)

Answer 1

jqwik目前没有直接将参数传递给提供者方法的机制。但是，注释机制应该按照您的建议工作：

@Property
void test(@ForAll("charSequence") @Length(min = 2, max = 5)  CharSequence cs) {
    System.out.println(cs);
}

@Provide
Arbitrary<CharSequence> charSequence(TypeUsage typeUsage) {
    Optional<Length> optionalLength = typeUsage.findAnnotation(Length.class);
    int minLength = optionalLength.map(l -> l.min()).orElse(1);
    int maxLength = optionalLength.map(l -> l.max()).orElse(255);

    Arbitrary<String> stringArbitrary = Arbitraries.strings().ofMinLength(minLength).ofMaxLength(maxLength);
    Arbitrary<StringBuffer> stringBufferArbitrary =
        stringArbitrary.map(str -> null == str ? null : new StringBuffer(str));
    Arbitrary<StringBuilder> stringBuilderArbitrary =
        stringArbitrary.map(str -> null == str ? null : new StringBuilder(str));

    return Arbitraries.oneOf(
            stringArbitrary, 
            stringBufferArbitrary, 
            stringBuilderArbitrary
    );
}

我猜你忘了打开@Length的运行时保留，否则注解将被编译器删除：

@Target({ ElementType.ANNOTATION_TYPE, ElementType.PARAMETER, ElementType.TYPE_USE })
@Retention(RetentionPolicy.RUNTIME)
@interface Length {
    int min();
    int max();
}

上面的代码应该生成类似于(长度在2到5之间的序列)的输出：

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