cljs.reader/read-string是否会为生成的表单附加元数据？

Great question! Let’s break this down clearly:

1. Is the statement true? #

Absolutely—cljs.reader/read-string does attach metadata to the forms it generates, including position information like line and column numbers from the input string.

You can easily test this with a quick snippet in ClojureScript:

(require '[cljs.reader :as reader])

;; Sample input string
(def code "(defn greet [name] (str \"Hello, \" name))")
;; Parse the string into a form
(def parsed-form (reader/read-string code))

;; Check the metadata attached to the top-level form
(meta parsed-form)
;; Returns something like: {:line 1, :column 1}

This metadata tracks where the form started in the original input string, which is super useful for tooling like linters, debuggers, or IDEs that need to map compiled code back to its source.

2. Is this documented officially? #

Yes, this behavior is covered in ClojureScript’s official documentation for cljs.reader/read-string.

The docs note that by default, the reader preserves source position metadata (:line and :column keys) for all parsed forms. Additionally, you can opt out of this behavior by passing the :read-meta false option to the reader:

;; Disable metadata reading
(def parsed-form-no-meta (reader/read-string {:read-meta false} code))
(meta parsed-form-no-meta) ;; Returns nil (no position metadata attached)

内容的提问来源于stack exchange，提问作者Gra