[PATCH v4] lisp/ob-screen.el: Support ~:var~ header args for babel blocks

[Max Nikulin <manikulin@gmail.com>]

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On 16/03/2023 17:22, Ihor Radchenko wrote:
> Canceled.

Anyway it does not work.

I have tried to "fix" `org-babel-variable-assignments:screen' by an 
extra patch. Perhaps executable name aka :cmd and babel language should 
not be rigidly coupled and it may be subject for further improvement.

Ken, you wrote that you have other patches for ob-screen.el. Do you plan 
to sent them?

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From a654876c33a13dafac865fa9ea88176302d810c2 Mon Sep 17 00:00:00 2001
From: "Kenneth D. Mankoff" <mankoff@gmail.com>
Date: Mon, 20 Feb 2023 21:40:39 -0800
Subject: [PATCH v4 1/2] ob-screen.el: Support var for screen source blocks

* lisp/ob-screen.el (org-babel-execute:screen): Parse header params
for `:var', then inject into screen session.
* etc/ORG-NEWS: Document as New Feature
---
 etc/ORG-NEWS      | 10 ++++++++++
 lisp/ob-screen.el |  8 ++++++++
 2 files changed, 18 insertions(+)

diff --git a/etc/ORG-NEWS b/etc/ORG-NEWS
index 4ca13af17..3f70dc99a 100644
--- a/etc/ORG-NEWS
+++ b/etc/ORG-NEWS
@@ -131,6 +131,16 @@ selection.
 TODO state, priority, tags, statistics cookies, and COMMENT keywords
 are allowed in the tree structure.
 
+*** ob-screen now supports :var header arguments
+
+The ~:var~ header arg is now supported.
+
+#+BEGIN_SRC org
+,#+BEGIN_SRC screen :var x=42
+,echo $x
+,#+END_SRC
+#+END_SRC
+
 ** Miscellaneous
 *** Remove undocumented ~:target~ header parameter in ~ob-clojure~
 
diff --git a/lisp/ob-screen.el b/lisp/ob-screen.el
index 269538e79..6e6a31ea6 100644
--- a/lisp/ob-screen.el
+++ b/lisp/ob-screen.el
@@ -40,6 +40,10 @@ (org-assert-version)
 
 (require 'ob)
 
+;; Reuse the variable assignment code from ob-shell
+(defalias 'org-babel-variable-assignments:screen
+  'org-babel-variable-assignments:shell)
+
 (defvar org-babel-screen-location "screen"
   "The command location for screen.
 In case you want to use a different screen than one selected by your $PATH")
@@ -55,8 +59,12 @@ (defun org-babel-execute:screen (body params)
   (message "Sending source code block to interactive terminal session...")
   (save-window-excursion
     (let* ((session (cdr (assq :session params)))
+           (var-lines (org-babel-variable-assignments:screen params))
            (socket (org-babel-screen-session-socketname session)))
       (unless socket (org-babel-prep-session:screen session params))
+      (mapcar (lambda (var)
+                (org-babel-screen-session-execute-string session var))
+              var-lines)
       (org-babel-screen-session-execute-string
        session (org-babel-expand-body:generic body params)))))
 
-- 
2.25.1


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From 1781c8986346a7ea894269f827cce80bfd5cfa70 Mon Sep 17 00:00:00 2001
From: Max Nikulin <manikulin@gmail.com>
Date: Thu, 16 Mar 2023 21:50:24 +0700
Subject: [PATCH v4 2/2] ob-screen.el: Do not rely on
 `org-babel-variable-assignments:shell'

* lisp/ob-screen.el (org-babel-variable-assignments:screen): Use `defun'
instead of `defalias' to call variable assignment function specific
to language obtained from the `:cmd' header argument.

`org-babel-variable-assignments:shell' might be considered as
implementation detail, see

Ihor Radchenko to emacs-orgmode. Re: [PATCH] lisp/ob-screen.el: Support
~:var~ header args for babel blocks. Sun, 26 Feb 2023 12:18:14 +0000.
<https://list.orgmode.org/87lekkzkl5.fsf@localhost>

The implemented approach is not optimal since it does not allow
to decouple interpreter executable (for example python3) and babel
language (for example python).
---
 lisp/ob-screen.el | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/lisp/ob-screen.el b/lisp/ob-screen.el
index 6e6a31ea6..5d09fe585 100644
--- a/lisp/ob-screen.el
+++ b/lisp/ob-screen.el
@@ -39,10 +39,23 @@ (require 'org-macs)
 (org-assert-version)
 
 (require 'ob)
-
-;; Reuse the variable assignment code from ob-shell
-(defalias 'org-babel-variable-assignments:screen
-  'org-babel-variable-assignments:shell)
+(require 'ob-shell)
+
+(defun org-babel-variable-assignments:screen (params)
+  "Return list of statements to assign block variables.
+
+This is an experimental feature, `:cmd' property from PARAMS
+treated as language while actually it is command (executable) name.
+It works at least for shell interpreters."
+  (and
+   (alist-get :var params)
+   (let* ((cmd (alist-get :cmd params))
+          (lang (and cmd (file-name-base cmd)))
+          (func (and lang (intern
+                           (concat "org-babel-variable-assignments:" lang)))))
+     (if (not (fboundp func))
+         (error "Babel language support for %s is not loaded" lang)
+       (funcall func params)))))
 
 (defvar org-babel-screen-location "screen"
   "The command location for screen.
-- 
2.25.1