Scheme version checks

And, if you happen to be launching it all the time, a way of skipping
them via a customizable variable.

Should address issue #15.

1 files changed, 25 insertions, 0 deletions

diff --git a/elisp/geiser-repl.el b/elisp/geiser-repl.el
index 68e4708..ebb74c2 100644
--- a/elisp/geiser-repl.el
+++ b/elisp/geiser-repl.el
@@ -105,6 +105,16 @@ expression, if any."
   :type 'boolean
   :group 'geiser-repl)
 
+(geiser-custom--defcustom geiser-repl-skip-version-check-p nil
+  "Whether to skip version checks for the Scheme executable.
+
+When set, Geiser won't check the version of the Scheme
+interpreter when starting a REPL, saving a few tenths of a
+second.
+"
+  :type 'boolean
+  :group 'geiser-repl)
+
 (geiser-custom--defcustom geiser-repl-query-on-exit-p nil
   "Whether to prompt for confirmation on \\[geiser-repl-exit]."
   :type 'boolean
@@ -188,6 +198,13 @@ module command as a string")
 (geiser-impl--define-caller geiser-repl--exit-cmd exit-command ()
   "Function returning the REPL exit command as a string")
 
+(geiser-impl--define-caller geiser-repl--version version-command (binary)
+  "Function returning the version of the corresponding scheme process,
+   given its full path.")
+
+(geiser-impl--define-caller geiser-repl--min-version minimum-version ()
+  "A variable providing the minimum required scheme version, as a string.")
+
 
 ;;; Geiser REPL buffers and processes:
 
@@ -355,6 +372,13 @@ module command as a string")
                                     geiser-repl-query-on-kill-p)
     (message "%s up and running!" (geiser-repl--repl-name impl))))
 
+(defun geiser-repl--check-version (impl)
+  (when (not geiser-repl-skip-version-check-p)
+    (let ((v (geiser-repl--version impl (geiser-repl--binary impl)))
+          (r (geiser-repl--min-version impl)))
+      (when (geiser--version< v r)
+        (error "Geiser requires %s version %s but detected %s" impl r v)))))
+
 (defun geiser-repl--start-scheme (impl address prompt)
   (setq comint-prompt-regexp prompt)
   (let* ((name (geiser-repl--repl-name impl))
@@ -363,6 +387,7 @@ module command as a string")
                  `(,(geiser-repl--binary impl)
                    nil
                    ,@(geiser-repl--arglist impl)))))
+    (when (not address) (geiser-repl--check-version impl))
     (condition-case err
         (apply 'make-comint-in-buffer `(,name ,buff ,@args))
       (error (insert "Unable to start REPL:\n"