macros - 将可选的文档字符串添加到 def* 宏

Question

我想将可选的文档字符串添加到我的 def* 宏中。例如:

(defmacro defhtml
  "Macro to avoid backtick unquote[splicing] in html vectors.
   TODO: Add optional docstring."
  [name args & body]
  `(defn ~name ~args (html ~@body)))

;; Working defhtml
(defhtml include-css [href]
  [:link {:href href :rel "stylesheet"}])

我愿意:

(defhtml include-css
  "My optional docstring here."
  [:link {:href href :rel "stylesheet"}])

我认为应该有一些通用的习语。

Answer 1

您需要确定宏的第二个参数是否为文档字符串(您可以测试它是否为字符串)。 Clojure 宏是 Clojure，因此您可以根据需要对传递给宏的表单执行任何逻辑或操作。如果不完全符合您的要求，这应该接近:

(defmacro defhtml [name & args]
  (cond
    ;; doc-string?
    (string? (first args))
    (let [[doc-string args-list & body] args]
      `(defn ~name ~doc-string ~args-list (html ~@body)))

    :no-doc-string
    (let [[args-list & body] args]
      `(defn ~name ~(format "HTML Generator %s" name) ~args-list (html ~@body)))))

这应该会产生您想要的宏扩展:

(defhtml include-css [href]
  [:link {:href href :rel "stylesheet"}])

产生:

(defn include-css
    "HTML Generator include-css"
  [href]
  (html [:link {:href href, :rel "stylesheet"}]))

同时:

(defhtml include-css
  "Standard css includes fory my site"
  [href]
  [:link {:href href :rel "stylesheet"}])

产生:

(defn include-css
    "Standard css includes fory my site"
  [href]
  (html [:link {:href href, :rel "stylesheet"}]))