Clojure：如何获取定义了地图的文件/行号？ [英] Clojure: How do I get the file/line number on which a map was defined?

问题描述

我知道我可以从元数据中获得：行和：file 然而，我正在建立一个系统，用户可以传递原始地图，我将最终链接在一起的数据在以后的时间。当此链接失败时，我想报告他们指定地图的文件/行。例如：

I know I can get the :line and :file from the metadata on a var; however, I'm building a system where the user can pass me raw maps and I will end up "linking" the data together at a later time. When this linkage fails, I'd like to report the file/line in which they specified the map. E.g.:

 (defn generate-stuff []
    (make-thing { :k (make-thing { :k v }) }
    )
 )

 (link (generate-stuff) (other-generator))
 ;; outputs file/line of the map containing the errant :k/v pair

将文件/行与集合的元数据相关联几乎肯定是要走的路，但由于没有任何var看看，我不知道在哪里得到行号。我看到get-line-number的定义，但它需要一个读者，虽然我可以找到所有的特殊读者和 * default-data-reader-fn * 数据读取器（这是nil），我似乎无法找出如何访问代码读取器。

I assume that writing a macro to associate file/line with the collection's metadata is almost certainly the way to go, but since there isn't any "var" to look at, I'm not sure where to get the line number. I see the definition of get-line-number, but it requires a reader, and while I can find all of the special readers and the *default-data-reader-fn* data reader (which is nil), I cannot seem to figure out how to access the "code" reader.

推荐答案

，看起来在宏中使用& form 是答案。我写了以下位的通用测试代码，它似乎工作：

OK, it looks like using &form in a macro is the answer. I wrote the following bit of generic test code, and it seems to work:

(defmacro make-thing [obj]
  (let [f *file*]
    (with-meta obj (assoc (meta &form) :file f))
  )
)

& form 是指调用宏的表单，行/列的元数据。特殊的var 文件具有源文件的相对路径。因此，将两个元素组合到对象上的元数据产生期望的结果。

The &form refers to the form that invoked the macro, and it has metadata for line/column. The special var file has the relative path of the source file. So, combining the two into the metadata onto the object results in the desired result.

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