[PATCH] Fix :var parameter for fish shell code blocks

[Elias Kueny <elias.kueny@posteo.net>]

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From 0d8067348d033e159a460233773e442c0775a8bb Mon Sep 17 00:00:00 2001
From: Elias Kueny <elias.kueny@posteo.net>
Date: Sat, 14 Oct 2023 00:20:55 +0200
Subject: [PATCH] lisp/ob-shell.el: Adapt the `:var' header parameter to fish

* ob-shell.el (org-babel-variable-assignments:shell): allow the `:var'
keyword on fish code blocks to work with fish variables.

The fish shell uses the syntax `set variable value' instead of
`value=value' to set a shell variable.  This caused org-babel to
return an syntax error when attempting to execute a fish code block
with a `:var' parameter.  This change adds a helper function to use
the correct format.

TINYCHANGE
---
 lisp/ob-shell.el | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/lisp/ob-shell.el b/lisp/ob-shell.el
index fe4c7af72..9f3b614e6 100644
--- a/lisp/ob-shell.el
+++ b/lisp/ob-shell.el
@@ -167,6 +167,11 @@ defun org-babel--variable-assignments:sh-generic
   "Return a list of statements declaring the values as a generic variable."
   (format "%s=%s" varname (org-babel-sh-var-to-sh values sep hline)))

+(defun org-babel--variable-assignments:fish
+    (varname values &optional sep hline)
+  "Return a list of statements declaring the values as a fish variable."
+  (format "set %s %s" varname (org-babel-sh-var-to-sh values sep hline)))
+
 (defun org-babel--variable-assignments:bash_array
     (varname values &optional sep hline)
   "Return a list of statements declaring the values as a bash array."
@@ -212,8 +217,11 @@ defun org-babel-variable-assignments:shell
        (if (string-suffix-p "bash" shell-file-name)
 	   (org-babel--variable-assignments:bash
             (car pair) (cdr pair) sep hline)
-         (org-babel--variable-assignments:sh-generic
-	  (car pair) (cdr pair) sep hline)))
+         (if (string-suffix-p "fish" shell-file-name)
+	     (org-babel--variable-assignments:fish
+              (car pair) (cdr pair) sep hline)
+           (org-babel--variable-assignments:sh-generic
+	    (car pair) (cdr pair) sep hline))))
      (org-babel--get-vars params))))

 (defun org-babel-sh-var-to-sh (var &optional sep hline)
--
2.41.0

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Hello,

I found an issue with fish shell code blocks, in that the `:var' parameter generates a command that is not syntaxically correct. Fish uses `set variable value' instead of `variable = value'. As a result, org-babel throws an error when executing the code block. This patch fixes this by adding an exception to org-babel-variable-assignments:shell on the model of what it already does for bash.

Example of code block triggering the error:
#+begin_src fish :var test
echo $test
#+end_src

Best regards,
Elias