Use default-directory as :dir when executing a source block

`default-directory` is already set according to :dir when executing a
source block. This prevents `org-babel-expand-body:jupyter` from
attempting to re-expand the value of the :dir header argument.
See #302.

Author: nnicandro

ob-jupyter.el

@@ -473,7 +473,15 @@ the PARAMS alist."
            (jupyter-current-client (buffer-local-value 'jupyter-current-client buf))
            (lang (jupyter-kernel-language jupyter-current-client))
            (vars (org-babel-variable-assignments:jupyter params lang))
-           (code (org-babel-expand-body:jupyter body params vars lang)))
+           (code (progn
+                   (when-let* ((dir (alist-get :dir params)))
+                     ;; `default-directory' is already set according
+                     ;; to :dir when executing a source block.  Set
+                     ;; :dir to the absolute path so that
+                     ;; `org-babel-expand-body:jupyter' does not try
+                     ;; to re-expand the path. See #302.
+                     (setf (alist-get :dir params) default-directory))
+                   (org-babel-expand-body:jupyter body params vars lang))))
       (pcase-let ((`(,req ,maybe-result)
                    (org-babel-jupyter--execute code async-p)))
         ;; KLUDGE: Remove the file result-parameter so that

test/jupyter-test.el

@@ -2862,7 +2862,18 @@ os.path.abspath(os.getcwd())"
         ;; See #302
         (jupyter-org-test-src-block
          "print(r\"\\r\")"
-         ": \\r\n")))))
+         ": \\r\n")))
+    (ert-info ("Relative directory")
+      ;; See #302
+      (let* ((temporary-file-directory jupyter-test-temporary-directory)
+             (dir (make-temp-file "dir-header-arg" t)))
+        ;; FIXME: Don't use an internal function here.
+        (jupyter-org-test
+         (let ((default-directory (file-name-directory dir)))
+           (jupyter-org-test-src-block-1
+            "print(\"hi\")"
+            ": hi\n" nil
+            `((:dir . ,(file-name-base dir))))))))))
 
 (ert-deftest jupyter-org--find-mime-types ()
   :tags '(org mime)