clojure.edn parser will not parse complete file in some cases

Question

I've noticed that clojure.edn parser will skip rest of the file if it manages to find the first valid token that will complete collection. For example:

;; demo.edn
{
 :foo 1
 :bar 2 }
 :baz 3 
}

with:

(require '[clojure.edn :as edn]
         '[clojure.java.io :as io])

(with-open [r (io/reader "demo.edn")]
  (edn/read (java.io.PushbackReader. r)))

user=> {:foo 1, :bar 2}

It will also ignore rest of the file when the file is clearly malformed:

{
 :foo 1
 :bar 2 }
xxxx yyyy }}}}} {{{{ ((
 :baz 3 

it returns again:

user=> {:foo 1, :bar 2}

I was expecting it to throw EOF exception or at least '}' mismatch. Is this behavior by design or a possible bug?

Answer 1

It's by design, all according to the docstring of edn/read:

Reads the next object from stream [...]

You can read multiple times from the same stream to get all of the objects and to validate the whole file.

(with-open [r (io/reader "demo.edn")]
  (loop []
    (let [data (edn/read (java.io.PushbackReader. r))]
      (println "Got data" data)
      (recur))))
Got data {:foo 1, :bar 2}
Got data :baz
Got data 3
Execution error at user/eval3609 (form-init10153318817371430115.clj:3).
Unmatched delimiter: }

Comments

Yeah, I've overlooked that part in docstring :D Thanks!