lang/org: disable ob-async on export or :session

Refactors advice to disable ob-async when exporting org documents or
when the :session parameter is present (ob-async does not support it).
Execution is degraded to synchronous execution and a warning logged.

modules/lang/org/README.org

@@ -134,6 +134,11 @@ https://www.mfoot.com/blog/2015/11/22/literate-emacs-configuration-with-org-mode
 
 
 ** Hacks
++ Adds support for a ~:sync~ parameter for org src blocks. This overrides
+  ~:async~.
++ Gracefully degrades ~:async~ babel blocks to ~:sync~ when =ob-async= would
+  cause errors or issues (such as with a ~:session~ parameter, which =ob-async=
+  does not support, or when exporting org documents).
 + The window is recentered when following links.
 + The breadcrumbs displayed in eldoc when hovering over an org headline has been
   reworked to strip out link syntax and normalize font-size disparities.

modules/lang/org/config.el

@@ -214,20 +214,28 @@ Is relative to `org-directory', unless it is absolute. Is used in Doom's default
   ;; won't likely complete in time, and will instead output an ob-async hash
   ;; instead of the wanted evaluation results.
   (after! ob
-    (add-to-list 'org-babel-default-lob-header-args '(:async . nil)))
+    (add-to-list 'org-babel-default-lob-header-args '(:sync)))
 
-  (defadvice! +org-inhibit-async-babel-blocks-on-export-a (orig-fn &optional fn arg info params)
+  (defadvice! +org-babel-disable-async-if-needed-a (orig-fn &optional fn arg info params)
-    "Exporting org documents with async blocks will sometimes substitute
+    "Disable ob-async when leaving it on would cause errors or issues.
-evaluation output with hashes in the exported document. This is because the
+
-block is executed asynchronously, but the exporter doesn't wait for it to
+Such as when exporting org documents or executing babel blocks with :session
-finish. This advice forces babel blocks to not execute asychronously when being
+parameters (which ob-async does not support), in which case this advice forces
-exported."
+these blocks to run synchronously.
+
+Also adds support for a `:sync' parameter to override `:async'."
     :around #'ob-async-org-babel-execute-src-block
-    (let ((async (or (assoc :async params)
+    (if (null fn)
-                     (assoc :async (nth 2 (or info (org-babel-get-src-block-info)))))))
+        (funcall orig-fn fn arg info params)
-      (if (and async (null (cdr async)))
+      (let* ((info (or info (org-babel-get-src-block-info)))
-          (funcall fn arg info params)
+             (params (org-babel-merge-params (nth 2 info) params)))
-        (funcall orig-fn fn arg info params))))
+        (cond ((or (assq :sync params)
+                   (not (assq :async params)))
+               (funcall fn arg info params))
+              ((not (member (cdr (assq :session params)) '("none" nil)))
+               (message "Org babel :: :session is incompatible with :async. Executing synchronously!")
+               nil)
+              ((funcall orig-fn fn arg info params))))))
 
   (defadvice! +org-fix-newline-and-indent-in-src-blocks-a (&optional indent _arg _interactive)
     "Mimic `newline-and-indent' in src blocks w/ lang-appropriate indentation."
@@ -306,7 +314,9 @@ exported."
                        ((stringp lang) (intern lang))))
            (lang (or (cdr (assq lang +org-babel-mode-alist))
                      lang)))
-      (+org--babel-lazy-load lang (assq :async (nth 2 info)))
+      (+org--babel-lazy-load
+       lang (and (not (assq :sync (nth 2 info)))
+                 (assq :async (nth 2 info))))
       t))
 
   (advice-add #'org-babel-do-load-languages :override #'ignore))