通过 Clojure Spec 执行带有命名参数的宏

Question

假设我们有一个宏，它接受一个必需的参数，后跟可选的位置参数，例如

(require '[clojure.spec     :as spec]
         '[clojure.spec.gen :as gen])

(defmacro dress [what & clothes]
  `(clojure.string/join " " '(~what ~@clothes)))

(dress "me")
=> "me"
(dress "me" :hat "favourite")
=> "me :hat favourite"

我们为它写了一个规范，比如

(spec/def ::hat string?)
(spec/fdef dress
           :args (spec/cat :what string?
                           :clothes (spec/keys* :opt-un [::hat]))
           :ret string?)

我们会发现spec/exercise-fn无法执行宏

(spec/exercise-fn `dress)
;1. Unhandled clojure.lang.ArityException
;   Wrong number of args (1) passed to: project/dress

即使函数生成器生成的数据被宏接受得很好:

(def args (gen/generate (spec/gen (spec/cat :what string?
                                            :clothes (spec/keys* :opt-un [::hat])))))
; args => ("mO792pj0x")
(eval `(dress ~@args))
=> "mO792pj0x"
(dress "mO792pj0x")
=> "mO792pj0x"

另一方面，定义一个函数并以相同的方式运行它也很好：

(defn dress [what & clothes]
  (clojure.string/join " " (conj clothes what)))

(spec/def ::hat string?)
(spec/fdef dress
           :args (spec/cat :what string?
                           :clothes (spec/keys* :opt-un [::hat]))
           :ret string?)
(dress "me")
=> "me"
(dress "me" :hat "favourite")
=> "me :hat favourite"
(spec/exercise-fn `dress)
=> ([("") ""] [("l" :hat "z") "l :hat z"] [("") ""] [("h") "h"] [("" :hat "") " :hat "] [("m") "m"] [("8ja" :hat "N5M754") "8ja :hat N5M754"] [("2vsH8" :hat "Z") "2vsH8 :hat Z"] [("" :hat "TL") " :hat TL"] [("q4gSi1") "q4gSi1"])

如果我们看一下具有相似定义模式的内置宏，我们会发现同样的问题：

(spec/exercise-fn `let)
; 1. Unhandled clojure.lang.ArityException
;    Wrong number of args (1) passed to: core/let

一件有趣的事情是 exercise-fn 在始终存在一个必需的命名参数时工作正常：

(defmacro dress [what & clothes]
  `(clojure.string/join " " '(~what ~@clothes)))

(spec/def ::hat string?)
(spec/def ::tie string?)
(spec/fdef dress
           :args (spec/cat :what string?
                           :clothes (spec/keys* :opt-un [::hat] :req-un [::tie]))
           :ret string?)
(dress "me" :tie "blue" :hat "favourite")
=> "me :tie blue :hat favourite"
(spec/exercise-fn `dress)

换句话说：似乎有一些隐藏的参数总是在正常调用期间传递给宏，而规范没有传递这些参数。遗憾的是，我对 Clojure 的经验不足，无法了解这些细节，但是一只小鸟告诉我，有一些东西名为 &env 和 &form。

但我的问题归结为：是否有可能以 spec/exercise-fn 可以很好地锻炼的方式指定带有命名参数的宏？

附录：

用 and 包装 keys* 似乎又破坏了 exercise-fn，即使它有一个必需的命名参数。

Answer 1

您不能将 exercise-fn 与宏一起使用，因为您不能将 apply 与宏一起使用。（注意这叫做练习 fn :).

这与 (apply dress ["foo"]) 完全一样，它会产生熟悉的 "can't take value of a macro"。您看到的不同错误消息是因为它应用于 var 而不是宏，因为真正发生的事情就像 (apply #'user/dress ["foo"])。

通过 Clojure Spec 执行带有命名参数的宏

Exercising macros with named arguments through Clojure Spec

clojure

clojure.spec