[Fix #1187] Allow ess-startup-directory to be a symbol

  .. and make it to take precedence over ess-startup-directory-function.

  Document the usage.

lisp/ess-custom.el

@@ -314,22 +314,22 @@ buffer.")
 (defvaralias 'ess-directory-function 'ess-startup-directory-function)
 (defcustom ess-startup-directory-function nil
   "Function to return the directory that ESS is run from.
-If nil or if the function returns nil then you get `ess-startup-directory'."
-  :group 'ess
-  :type '(choice (const nil) function))
-
-(defcustom ess-setup-directory-function nil
-  "Function to setup the directory that ESS is run from.
-This function can be called to set environment variables or to create
-a workspace."
+Value of `ess-startup-directory' has precedence over this function."
   :group 'ess
   :type '(choice (const nil) function))
 
 (defvaralias 'ess-directory 'ess-startup-directory)
 (defcustom ess-startup-directory nil
-  "The directory ESS is run from.  It must end in a slash.
-Provided as a default if `ess-ask-for-ess-directory' is non-nil.
-A nil value means use the current buffer's default directory."
+  "The directory ESS is run from (string or a symbol).
+Provided a default (especially useful if
+`ess-ask-for-ess-directory' is non-nil). A nil value means use
+the value returned by `ess-startup-directory-function'. If nil,
+use current project directory, otherwise use to the
+`default-directory'.
+
+When this variable is a symbol, use its value. Set this variable
+to `'default-directory' in order to always start in the current
+directory."
   :group 'ess
   :type '(choice (const nil) directory))
 

lisp/ess-inf.el

@@ -622,11 +622,14 @@ process-less buffer because it was created with
 ;;*;; Requester functions called at startup
 (defun inferior-ess--get-startup-directory ()
   "Return a startup directory."
-  (let ((dir (or (and ess-directory-function
-                      (funcall ess-directory-function))
+  (let ((dir (or (when (boundp 'ess-startup-directory)
+                   (if (symbolp ess-startup-directory)
+                       (symbol-value ess-startup-directory)
+                     ess-startup-directory))
+                 (and ess-startup-directory-function
+                      (funcall ess-startup-directory-function))
                  (when-let ((proj (project-current)))
                    (ess--project-root proj))
-                 ess-startup-directory
                  default-directory)))
     (directory-file-name dir)))
 
@@ -2429,7 +2432,7 @@ START-ARGS gets passed to the dialect-specific
       ;; Make sure we don't ask for directory again
       ;; Use current working directory as default
       (let ((project-find-functions nil)
-            (ess-directory-function nil)
+            (ess-startup-directory-function nil)
             (ess-startup-directory (ess-get-process-variable 'default-directory))
             (ess-ask-for-ess-directory nil))
         (ess-quit 'no-save)

lisp/ess-r-mode.el

@@ -558,8 +558,10 @@ will be prompted to enter arguments interactively."
     "\n(R): ess-dialect=%s, buf=%s, start-arg=%s\n current-prefix-arg=%s\n"
     ess-dialect (current-buffer) start-args current-prefix-arg))
   (unless (or (file-remote-p default-directory)
-              (and ess-startup-directory
-                   (file-remote-p ess-startup-directory))
+              (when ess-startup-directory
+                (file-remote-p (if (symbolp ess-startup-directory)
+                                   (symbol-value ess-startup-directory)
+                                 ess-startup-directory)))
               ;; TODO: Once we drop Emacs 26 support, can probably
               ;; just use the REMOTE argument of `executable-find'.
               (executable-find inferior-ess-r-program))

lisp/ess-sp6-d.el

@@ -76,8 +76,7 @@
      (inferior-ess-help-command        . "help(\"%s\", pager=\"slynx -dump\", window=FALSE)\n")
      (inferior-ess-search-list-command . "searchPaths()\n")
 
-     (ess-directory-function           . S+-directory-function)
-     (ess-setup-directory-function     . S+-setup-directory-function)
+     (ess-startup-directory-function   . S+-directory-function)
      (ess-STERM                        . "iESS"))
    S+common-cust-alist)