eLisp: Save and parse JSON

my-custom-config-loader.el

;; to save an object into a json file
(with-temp-buffer
  (json-insert '(:foo "bar"))
  (write-file "~/tmp/my.json"))

;; load a json file as hash table 
(with-temp-buffer
  (insert-file-contents "~/tmp/my.json")
  (json-parse-buffer))

Each time you call json-insert a new JSON object is appended to the contents of the temp buffer. That is after the first section of your code the file looks like ⬇️ which is invalid json.

{"foo": "bar"}
{"test": "hallo"}

The idea is to call json-insert only once with the final configs object to be saved. For example:

(with-temp-buffer
  (let ((configs-to-be-saved '(:foo "bar")))
    (plist-put configs-to-be-saved
               :baz
               '(:x 10 :y "lorem"))
    (json-insert configs-to-be-saved)
    (write-file "~/tmp/my.json")))