Be less ambiguous when encoding/decoding messages

- Do not handle nil as an empty dictionary when encoding.

- Use the default `json-array-type`

jupyter-base.el

@@ -336,15 +336,12 @@ the ROUTING-ID of the socket. Return the created socket."
 
 (defun jupyter-read-plist (file)
   "Read a JSON encoded FILE as a property list."
-  (let ((json-object-type 'plist)
-        (json-array-type 'list)
-        (json-false nil))
+  (let ((json-object-type 'plist))
     (json-read-file file)))
 
 (defun jupyter-read-plist-from-string (string)
-  (let ((json-object-type 'plist)
-        ;; TODO: See the comment in `jupyter--decode'
-        (json-array-type 'list))
+  "Read a property list from a JSON encoded STRING."
+  (let ((json-object-type 'plist))
     (json-read-from-string string)))
 
 (provide 'jupyter-base)

jupyter-kernel-manager.el

@@ -200,7 +200,7 @@ kernel. Starting a kernel involves the following steps:
               (proc (jupyter--start-kernel
                      manager kernel-name (plist-get spec :env)
                      (cl-loop
-                      for arg in (plist-get spec :argv)
+                      for arg in (append (plist-get spec :argv) nil)
                       if (equal arg "{connection_file}")
                       collect conn-file
                       else if (equal arg "{resource_dir}")

jupyter-messages.el

@@ -91,8 +91,7 @@ They are all set to appropriate default values."
   (cl-letf (((symbol-function 'json-encode)
              (lambda (object)
                (cond ((memq object (list t json-null json-false))
-                      (if (eq object json-null) "{}"
-                        (json-encode-keyword object)))
+                      (json-encode-keyword object))
                      ((stringp object)      (json-encode-string object))
                      ((keywordp object)
                       ;; Handle `jupyter-message-type'
@@ -107,14 +106,16 @@ They are all set to appropriate default values."
                      ((listp object)        (json-encode-list object))
                      (t                     (signal 'json-error (list object)))))))
     (encode-coding-string
-     (if (stringp object) object (json-encode-plist object))
+     (cond
+      ((stringp object) object)
+      ;; FIXME: This seems expensive
+      ((json-plist-p object) (json-encode-plist object))
+      (t (json-encode object)))
      'utf-8 t)))
 
 (defun jupyter--decode (str)
   (setq str (decode-coding-string str 'utf-8))
   (let* ((json-object-type 'plist)
-         (json-array-type 'list)
-         (json-false nil)
          (val (condition-case nil
                   (json-read-from-string str)
                 ;; If it can't be read as JSON, assume its just a regular
@@ -233,7 +234,9 @@ They are all set to appropriate default values."
                                            code
                                            (silent nil)
                                            (store-history t)
-                                           (user-expressions nil)
+                                           ;; This needs to be an empty
+                                           ;; dictionary is not specified
+                                           (user-expressions #s(hash-table))
                                            (allow-stdin t)
                                            (stop-on-error nil))
   (cl-check-type code string)

jupyter-repl.el

@@ -957,7 +957,7 @@ lines then truncate it to something less than
 (defun jupyter-repl--handle-payload (payload)
   "Do the client actions in PAYLOAD."
   (cl-loop
-   for pl in payload
+   for pl across payload
    do (pcase (plist-get pl :source)
         ("page"
          (let ((text (plist-get (plist-get pl :data) :text/plain))
@@ -1226,7 +1226,8 @@ REPL buffer."
 
 (cl-defmethod jupyter-handle-history-reply ((client jupyter-repl-client) _req history)
   (with-jupyter-repl-buffer client
-    (cl-loop for (_session _line-number input-output) in history
+    (cl-loop for elem across history
+             for input-output = (aref elem 2)
              do (ring-remove+insert+extend jupyter-repl-history input-output))))
 
 (cl-defmethod jupyter-handle-is-complete-reply ((client jupyter-repl-client) _req status indent)
@@ -1480,8 +1481,9 @@ value that PREFIX takes.
 
 This function constructs candidates assuming that `company-mode'
 is used for completion."
-  (let ((types (plist-get metadata :_jupyter_types_experimental))
+  (let* ((matches (append matches nil))
          (tail matches)
+         (types (append (plist-get metadata :_jupyter_types_experimental) nil))
          ;; TODO: Handle the case when the matches are method signatures in the
          ;; Julia kernel. This information would be useful for doing some kind
          ;; of eldoc like feature.