Add pandoc conversion of rich outputs (#97)

README.org

@@ -490,6 +490,13 @@ generated image file names.
 Whenever you run a code block multiple times and replace its results, before
 the results are replaced, any generated files will be deleted to reduce the
 clutter in =org-babel-jupyter-resource-directory=.
+**** Convert rich kernel output with the =:pandoc= header argument
+
+By default html, markdown, and latex results are wrapped in a =BEGIN_EXPORT=
+block. If the header argument =:pandoc t= is set, they are instead
+converted to org-mode format with [[https://pandoc.org/][pandoc]]. You can control which outputs get
+converted with the custom variable =jupyter-org-pandoc-convertable=.
+
 *** Editing the contents of a code block
 
 When editing a Jupyter code block's contents, i.e. by pressing =C-c '= when at

jupyter-mime.el

@@ -625,6 +625,38 @@ message."
       (when (= (point) (point-min))
         (error "No display matching id (%s)" id)))))
 
+;;; Pandoc
+
+(defun jupyter-pandoc-convert (from to from-string &optional callback)
+  "Use pandoc to convert a string in FROM format to TO format.
+Starts a process and converts FROM-STRING, assumed to be in FROM
+format, to a string in TO format and returns the converted
+string.
+
+If CALLBACK is specified, return the process object. When the
+process exits, call CALLBACK with zero arguments and with the
+buffer containing the converted string current."
+  (cl-assert (executable-find "pandoc"))
+  (let* ((process-connection-type nil)
+         (proc (start-process
+                "jupyter-pandoc"
+                (generate-new-buffer " *jupyter-pandoc*")
+                "pandoc" "-f" from "-t" to "--")))
+    (set-process-sentinel
+     proc (lambda (proc _)
+            (when (memq (process-status proc) '(exit signal))
+              (with-current-buffer (process-buffer proc)
+                (funcall callback)
+                (kill-buffer (process-buffer proc))))))
+    (process-send-string proc from-string)
+    (process-send-eof proc)
+    (if callback proc
+      (let ((to-string ""))
+        (setq callback (lambda () (setq to-string (buffer-string))))
+        (while (zerop (length to-string))
+          (accept-process-output nil 1))
+        to-string))))
+
 (provide 'jupyter-mime)
 
 ;;; jupyter-mime.el ends here

jupyter-org-client.el

@@ -66,6 +66,12 @@ automatically be shown if this is non-nil."
   :group 'ob-jupyter
   :type 'boolean)
 
+(defcustom jupyter-org-pandoc-convertable
+  '("html" "markdown" "latex")
+  "Export blocks to convert to org-mode when ':pandoc t' header is set."
+  :group 'ob-jupyter
+  :type 'string)
+
 (defconst jupyter-org-mime-types '(:text/org
                                    ;; Prioritize images over html
                                    :image/svg+xml :image/jpeg :image/png
@@ -648,6 +654,16 @@ inserted without modification as the result of a code block."
   "Return a comment `org-element' with VALUE."
   (list 'comment (list :value value)))
 
+(defun jupyter-org-export-block-or-pandoc (type value params)
+  "Returns VALUE, either converted with pandoc or in an export block.
+If PARAMS has non-nil value for key ':pandoc' and TYPE is in
+`jupyter-org-pandoc-convertable', convert the result with pandoc.
+Otherwise, wrap it in an export block."
+  (if (and (alist-get :pandoc params)
+           (member type jupyter-org-pandoc-convertable))
+      (jupyter-org-raw-string (jupyter-pandoc-convert type "org" value))
+    (jupyter-org-export-block type value)))
+
 (defun jupyter-org-export-block (type value)
   "Return an export-block `org-element'.
 The block will export TYPE and the contents of the block will be
@@ -955,9 +971,9 @@ passed to Jupyter org-mode source blocks."
                                   &optional metadata)
   (jupyter-org--image-result mime params nil data metadata))
 
-(cl-defmethod jupyter-org-result ((_mime (eql :text/markdown)) _params data
+(cl-defmethod jupyter-org-result ((_mime (eql :text/markdown)) params data
                                   &optional _metadata)
-  (jupyter-org-export-block "markdown" data))
+  (jupyter-org-export-block-or-pandoc "markdown" data params))
 
 (defun jupyter-org--parse-latex-element (data)
   "Return a latex-fragment or latex-environment org-element obtained from DATA.
@@ -989,11 +1005,11 @@ parsed, wrap DATA in a minipage environment and return it."
                                   &optional _metadata)
   (if (member "raw" (alist-get :result-params params))
       (jupyter-org--parse-latex-element data)
-    (jupyter-org-export-block "latex" data)))
+    (jupyter-org-export-block-or-pandoc "latex" data params)))
 
-(cl-defmethod jupyter-org-result ((_mime (eql :text/html)) _params data
+(cl-defmethod jupyter-org-result ((_mime (eql :text/html)) params data
                                   &optional _metadata)
-  (jupyter-org-export-block "html" data))
+  (jupyter-org-export-block-or-pandoc "html" data params))
 
 ;; NOTE: The order of :around methods is that the more specialized wraps the
 ;; more general, this makes sense since it is how the primary methods work as