ob-comint.el, ob-python.el: Async session evaluation

Adds functionality to ob-comint.el to implement async session eval on
a per-language basis.  Adds a reference implementation for ob-python.

* lisp/ob-comint.el (org-babel-comint-with-output): Remove comment.
(org-babel-comint-async-indicator, org-babel-comint-async-buffers,
org-babel-comint-async-file-callback,
org-babel-comint-async-chunk-callback,
org-babel-comint-async-dangling): Add buffer-local variables used for
async comint evaluation.
(org-babel-comint-use-async): Add function to determine whether block
should be evaluated asynchronously.
(org-babel-comint-async-filter): Add filter function to attach to
comint-output-filter-functions for babel async eval.
(org-babel-comint-async-register): Add function to setup buffer
variables and hooks for session eval.
(org-babel-comint-async-delete-dangling-and-eval): Add helper function
for async session eval.

* lisp/ob-python.el (org-babel-execute:python): Check for async header
argument.
(org-babel-python-evaluate): Check whether to use async evaluation.
(org-babel-python-async-indicator): Add constant for indicating the
start/end of async evaluations.
(org-babel-python-async-evaluate-session): Add function for Python
async eval.

*
testing/lisp/test-ob-python.el (test-ob-python/async-simple-session-output):
Unit test for Python async session eval.
(test-ob-python/async-named-output): Unit test that Python async eval
can replace named output.
(test-ob-python/async-output-drawer): Unit test that Python async eval
works with drawer results.

etc/ORG-NEWS

@@ -316,6 +316,21 @@ package, to convert pandas Dataframes into orgmode tables:
 | 2 | 3 | 6 |
 #+end_src
 
+*** Async session evaluation
+
+The =:async= header argument can be used for asynchronous evaluation
+in session blocks for certain languages.
+
+Currently, async evaluation is supported in Python.  There is also
+functionality to implement async evaluation in other languages that
+use comint, but this needs to be done on a per-language basis.
+
+By default, async evaluation is disabled unless the =:async= header
+argument is present.  You can also set =:async no= to force it off
+(for example if you've set =:async= in a property drawer).
+
+Async evaluation is disabled during export.
+
 ** Miscellaneous
 *** Missing or empty placeholders in "eval" macros are now =nil=
 They used to be the empty string.

lisp/ob-comint.el

@@ -93,12 +93,7 @@ or user `keyboard-quit' during execution of body."
 			       (regexp-quote ,eoe-indicator) nil t)
 			      (re-search-forward
 			       comint-prompt-regexp nil t)))))
-	   (accept-process-output (get-buffer-process (current-buffer)))
-	   ;; thought the following this would allow async
-	   ;; background running, but I was wrong...
-	   ;; (run-with-timer .5 .5 'accept-process-output
-	   ;; 		 (get-buffer-process (current-buffer)))
-	   )
+	   (accept-process-output (get-buffer-process (current-buffer))))
 	 ;; replace cut dangling text
 	 (goto-char (process-mark (get-buffer-process (current-buffer))))
 	 (insert dangling-text)
@@ -147,6 +142,171 @@ FILE exists at end of evaluation."
    (if (= (aref string (1- (length string))) ?\n) string (concat string "\n")))
   (while (not (file-exists-p file)) (sit-for (or period 0.25))))
 
+
+;;; Async evaluation
+
+(defvar-local org-babel-comint-async-indicator nil
+  "Regular expression that `org-babel-comint-async-filter' scans for.
+It should have 2 parenthesized expressions,
+e.g. \"org_babel_async_\\(start\\|end\\|file\\)_\\(.*\\)\".  The
+first parenthesized expression determines whether the token is
+delimiting a result block, or whether the result is in a file.
+If delimiting a block, the second expression gives a UUID for the
+location to insert the result.  Otherwise, the result is in a tmp
+file, and the second expression gives the file name.")
+
+(defvar-local org-babel-comint-async-buffers nil
+  "List of Org mode buffers to check for Babel async output results.")
+
+(defvar-local org-babel-comint-async-file-callback nil
+  "Callback to clean and insert Babel async results from a temp file.
+The callback function takes two arguments: the alist of params of the Babel
+source block, and the name of the temp file.")
+
+(defvar-local org-babel-comint-async-chunk-callback nil
+  "Callback function to clean Babel async output results before insertion.
+Its single argument is a string consisting of output from the
+comint process.  It should return a string that will be be passed
+to `org-babel-insert-result'.")
+
+(defvar-local org-babel-comint-async-dangling nil
+  "Dangling piece of the last process output, in case
+`org-babel-comint-async-indicator' is spread across multiple
+comint outputs due to buffering.")
+
+(defun org-babel-comint-use-async (params)
+  "Determine whether to use session async evaluation.
+PARAMS are the header arguments as passed to
+`org-babel-execute:lang'."
+  (let ((async (assq :async params))
+        (session (assq :session params)))
+    (and async
+	 (not org-babel-exp-reference-buffer)
+         (not (equal (cdr async) "no"))
+         (not (equal (cdr session) "none")))))
+
+(defun org-babel-comint-async-filter (string)
+  "Captures Babel async output from comint buffer back to Org mode buffers.
+This function is added as a hook to `comint-output-filter-functions'.
+STRING contains the output originally inserted into the comint buffer."
+  ;; Remove outdated Org mode buffers
+  (setq org-babel-comint-async-buffers
+	(cl-loop for buf in org-babel-comint-async-buffers
+	      if (buffer-live-p buf)
+	      collect buf))
+  (let* ((indicator org-babel-comint-async-indicator)
+	 (org-buffers org-babel-comint-async-buffers)
+	 (file-callback org-babel-comint-async-file-callback)
+	 (combined-string (concat org-babel-comint-async-dangling string))
+	 (new-dangling combined-string)
+	 ;; list of UUID's matched by `org-babel-comint-async-indicator'
+	 uuid-list)
+    (with-temp-buffer
+      (insert combined-string)
+      (goto-char (point-min))
+      (while (re-search-forward indicator nil t)
+	;; update dangling
+	(setq new-dangling (buffer-substring (point) (point-max)))
+	(cond ((equal (match-string 1) "end")
+	       ;; save UUID for insertion later
+	       (push (match-string 2) uuid-list))
+	      ((equal (match-string 1) "file")
+	       ;; insert results from tmp-file
+	       (let ((tmp-file (match-string 2)))
+		 (cl-loop for buf in org-buffers
+		       until
+		       (with-current-buffer buf
+			 (save-excursion
+			   (goto-char (point-min))
+			   (when (search-forward tmp-file nil t)
+			     (org-babel-previous-src-block)
+                             (let* ((info (org-babel-get-src-block-info))
+                                    (params (nth 2 info))
+                                    (result-params
+                                     (cdr (assq :result-params params))))
+                               (org-babel-insert-result
+                                 (funcall file-callback
+                                          (nth
+                                           2 (org-babel-get-src-block-info))
+                                          tmp-file)
+                                result-params info))
+			     t))))))))
+      ;; Truncate dangling to only the most recent output
+      (when (> (length new-dangling) (length string))
+	(setq new-dangling string)))
+    (setq-local org-babel-comint-async-dangling new-dangling)
+    (when uuid-list
+      ;; Search for results in the comint buffer
+      (save-excursion
+	(goto-char (point-max))
+	(while uuid-list
+	  (re-search-backward indicator)
+	  (when (equal (match-string 1) "end")
+	    (let* ((uuid (match-string-no-properties 2))
+		   (res-str-raw
+		    (buffer-substring
+		     ;; move point to beginning of indicator
+                     (- (match-beginning 0) 1)
+		     ;; find the matching start indicator
+		     (cl-loop
+                      do (re-search-backward indicator)
+		      until (and (equal (match-string 1) "start")
+				 (equal (match-string 2) uuid))
+		      finally return (+ 1 (match-end 0)))))
+		   ;; Apply callback to clean up the result
+		   (res-str (funcall org-babel-comint-async-chunk-callback
+                                     res-str-raw)))
+	      ;; Search for uuid in associated org-buffers to insert results
+	      (cl-loop for buf in org-buffers
+		    until (with-current-buffer buf
+			    (save-excursion
+			      (goto-char (point-min))
+			      (when (search-forward uuid nil t)
+				(org-babel-previous-src-block)
+                                (let* ((info (org-babel-get-src-block-info))
+                                       (params (nth 2 info))
+                                       (result-params
+                                        (cdr (assq :result-params params))))
+				  (org-babel-insert-result
+                                   res-str result-params info))
+				t))))
+	      ;; Remove uuid from the list to search for
+	      (setq uuid-list (delete uuid uuid-list)))))))))
+
+(defun org-babel-comint-async-register
+    (session-buffer org-buffer indicator-regexp
+		    chunk-callback file-callback)
+  "Sets local org-babel-comint-async variables in SESSION-BUFFER.
+ORG-BUFFER is added to `org-babel-comint-async-buffers' if not
+present.  `org-babel-comint-async-indicator',
+`org-babel-comint-async-chunk-callback', and
+`org-babel-comint-async-file-callback' are set to
+INDICATOR-REGEXP, CHUNK-CALLBACK, and FILE-CALLBACK
+respectively."
+  (org-babel-comint-in-buffer session-buffer
+    (setq org-babel-comint-async-indicator indicator-regexp
+	  org-babel-comint-async-chunk-callback chunk-callback
+	  org-babel-comint-async-file-callback file-callback)
+    (unless (memq org-buffer org-babel-comint-async-buffers)
+      (setq org-babel-comint-async-buffers
+	    (cons org-buffer org-babel-comint-async-buffers)))
+    (add-hook 'comint-output-filter-functions
+	      'org-babel-comint-async-filter nil t)))
+
+(defmacro org-babel-comint-async-delete-dangling-and-eval
+    (session-buffer &rest body)
+  "Remove dangling text in SESSION-BUFFER and evaluate BODY.
+This is analogous to `org-babel-comint-with-output', but meant
+for asynchronous output, and much shorter because inserting the
+result is delegated to `org-babel-comint-async-filter'."
+  (declare (indent 1) (debug t))
+  `(org-babel-comint-in-buffer ,session-buffer
+     (goto-char (process-mark (get-buffer-process (current-buffer))))
+     (delete-region (point) (point-max))
+     ,@body))
+
 (provide 'ob-comint)
 
+
+
 ;;; ob-comint.el ends here

lisp/ob-python.el

@@ -84,6 +84,7 @@ This function is called by `org-babel-execute-src-block'."
 	 (return-val (when (eq result-type 'value)
 		       (cdr (assq :return params))))
 	 (preamble (cdr (assq :preamble params)))
+	 (async (org-babel-comint-use-async params))
          (full-body
 	  (concat
 	   (org-babel-expand-body:generic
@@ -92,7 +93,8 @@ This function is called by `org-babel-execute-src-block'."
 	   (when return-val
 	     (format (if session "\n%s" "\nreturn %s") return-val))))
          (result (org-babel-python-evaluate
-		  session full-body result-type result-params preamble)))
+		  session full-body result-type
+		  result-params preamble async)))
     (org-babel-reassemble-table
      result
      (org-babel-pick-name (cdr (assq :colname-names params))
@@ -278,11 +280,14 @@ else:
 	  (if (member "pp" result-params) "True" "False")))
 
 (defun org-babel-python-evaluate
-  (session body &optional result-type result-params preamble)
+  (session body &optional result-type result-params preamble async)
   "Evaluate BODY as Python code."
   (if session
-      (org-babel-python-evaluate-session
-       session body result-type result-params)
+      (if async
+	  (org-babel-python-async-evaluate-session
+	   session body result-type result-params)
+	(org-babel-python-evaluate-session
+	 session body result-type result-params))
     (org-babel-python-evaluate-external-process
      body result-type result-params preamble)))
 
@@ -391,6 +396,49 @@ last statement in BODY, as elisp."
       (substring string 1 -1)
     string))
 
+;; Async session eval
+
+(defconst org-babel-python-async-indicator "print ('ob_comint_async_python_%s_%s')")
+
+(defun org-babel-python-async-value-callback (params tmp-file)
+  (let ((result-params (cdr (assq :result-params params)))
+	(results (org-babel-eval-read-file tmp-file)))
+    (org-babel-result-cond result-params
+      results
+      (org-babel-python-table-or-string results))))
+
+(defun org-babel-python-async-evaluate-session
+    (session body &optional result-type result-params)
+  "Asynchronously evaluate BODY in SESSION.
+Returns a placeholder string for insertion, to later be replaced
+by `org-babel-comint-async-filter'."
+  (org-babel-comint-async-register
+   session (current-buffer)
+   "ob_comint_async_python_\\(.+\\)_\\(.+\\)"
+   'org-babel-chomp 'org-babel-python-async-value-callback)
+  (let ((python-shell-buffer-name (org-babel-python-without-earmuffs session)))
+    (pcase result-type
+      (`output
+       (let ((uuid (md5 (number-to-string (random 100000000)))))
+         (with-temp-buffer
+           (insert (format org-babel-python-async-indicator "start" uuid))
+           (insert "\n")
+           (insert body)
+           (insert "\n")
+           (insert (format org-babel-python-async-indicator "end" uuid))
+           (python-shell-send-buffer))
+         uuid))
+      (`value
+       (let ((tmp-results-file (org-babel-temp-file "python-"))
+             (tmp-src-file (org-babel-temp-file "python-")))
+         (with-temp-file tmp-src-file (insert body))
+         (with-temp-buffer
+           (insert (org-babel-python-format-session-value tmp-src-file tmp-results-file result-params))
+           (insert "\n")
+           (insert (format org-babel-python-async-indicator "file" tmp-results-file))
+           (python-shell-send-buffer))
+         tmp-results-file)))))
+
 (provide 'ob-python)
 
 ;;; ob-python.el ends here

testing/lisp/test-ob-python.el

@@ -207,6 +207,67 @@ time.sleep(.1)
 #+end_src"
 	    (org-babel-execute-src-block)))))
 
+(ert-deftest test-ob-python/async-simple-session-output ()
+  (let ((org-babel-temporary-directory temporary-file-directory)
+        (org-confirm-babel-evaluate nil))
+    (org-test-with-temp-text
+     "#+begin_src python :session :async yes :results output
+import time
+time.sleep(.1)
+print('Yep!')
+#+end_src\n"
+     (should (let ((expected "Yep!"))
+	       (and (not (string= expected (org-babel-execute-src-block)))
+		    (string= expected
+			     (progn
+			       (sleep-for 0 200)
+			       (goto-char (org-babel-where-is-src-block-result))
+			       (org-babel-read-result)))))))))
+
+(ert-deftest test-ob-python/async-named-output ()
+  (let (org-confirm-babel-evaluate
+        (org-babel-temporary-directory temporary-file-directory)
+        (src-block "#+begin_src python :async :session :results output
+print(\"Yep!\")
+#+end_src")
+        (results-before "
+
+#+NAME: foobar
+#+RESULTS:
+: Nope!")
+        (results-after "
+
+#+NAME: foobar
+#+RESULTS:
+: Yep!
+"))
+    (org-test-with-temp-text
+     (concat src-block results-before)
+     (should (progn (org-babel-execute-src-block)
+                    (sleep-for 0 200)
+                    (string= (concat src-block results-after)
+                             (buffer-string)))))))
+
+(ert-deftest test-ob-python/async-output-drawer ()
+  (let (org-confirm-babel-evaluate
+        (org-babel-temporary-directory temporary-file-directory)
+        (src-block "#+begin_src python :async :session :results output drawer
+print(list(range(3)))
+#+end_src")
+        (result "
+
+#+RESULTS:
+:results:
+[0, 1, 2]
+:end:
+"))
+    (org-test-with-temp-text
+     src-block
+     (should (progn (org-babel-execute-src-block)
+                    (sleep-for 0 200)
+                    (string= (concat src-block result)
+                             (buffer-string)))))))
+
 (provide 'test-ob-python)
 
 ;;; test-ob-python.el ends here