Make do with a single connection

Separate connections for the REPL and Geiser commands was kind of
neat, but it had the problem of synchronising the current namespace
for both connections. A quick fix would have been to ask the scheme
for the current namespace for every Geiser command in the REPL, but
that, besides clunky, would add potentially prohibitive overhead for
(real) remote connections.

As it happens, using a single connection turned out to be not that
difficult and relatively clean code-wise. We could even turn back to
not use inferior schemes, and the net result of this refactoring would
be the replacement of comint-redirect (which wasn't able to match the
whole EOT token if it didn't arrive all at once) by transaction queues
(which also makes geiser-connection's implementation cleaner).

But using an inferior scheme has a dog-food value, and allows external
processes to connect to the scheme being used by Geiser without
further ado, which could be useful for debugging (although this is a
lame excuse: nothing prevents you from starting a REPL server from
emacs if you want). We'll see.

1 files changed, 31 insertions, 18 deletions

diff --git a/elisp/geiser-connection.el b/elisp/geiser-connection.el
index 76ba24a..0225964 100644
--- a/elisp/geiser-connection.el
+++ b/elisp/geiser-connection.el
@@ -74,37 +74,48 @@
   (format "\\(%s%s\\)" prompt (if debug (format "\\|%s" debug) "")))
 
 (defun geiser-con--connection-eot-re (prompt debug)
-  (geiser-con--combined-prompt (format "\0\n%s" prompt)
+  (geiser-con--combined-prompt (format "\n%s" prompt)
                                (and debug (format "\n%s" debug))))
 
 (defun geiser-con--make-connection (proc prompt debug-prompt)
-  (list :geiser-connection
+  (list t
+        (cons :filter (process-filter proc))
         (cons :tq (tq-create proc))
+        (cons :tq-filter (process-filter proc))
         (cons :eot (geiser-con--connection-eot-re prompt debug-prompt))
         (cons :prompt prompt)
         (cons :debug-prompt debug-prompt)
         (cons :count 0)
         (cons :completed (make-hash-table :weakness 'value))))
 
-(defun geiser-con--connection-swap-proc (con proc)
-  (let* ((this-proc (geiser-con--connection-process con))
-         (this-filter (process-filter this-proc))
-         (filter (process-filter proc))
-         (buffer (process-buffer proc))
-         (tq (geiser-con--connection-tq con)))
-    (set-process-filter this-proc filter)
-    (set-process-buffer this-proc buffer)
-    (set-process-filter proc this-filter)
-    (set-process-buffer proc nil)
-    (setcdr tq (cons proc (tq-buffer tq)))
-    this-proc))
-
-(defsubst geiser-con--connection-p (c)
-  (and (listp c) (eq (car c) :geiser-connection)))
+(defun geiser-con--connection-deactivate (c)
+  (when (car c)
+    (let* ((tq (geiser-con--connection-tq c))
+           (proc (geiser-con--connection-process c))
+           (proc-filter (geiser-con--connection-filter c)))
+      (while (not (tq-queue-empty tq))
+        (accept-process-output proc 0.1))
+      (set-process-filter proc proc-filter)
+      (setcar c nil))))
+
+(defun geiser-con--connection-activate (c)
+  (when (not (car c))
+    (let* ((tq (geiser-con--connection-tq c))
+           (proc (geiser-con--connection-process c))
+           (tq-filter (geiser-con--connection-tq-filter c)))
+      (while (accept-process-output proc 0.01))
+      (set-process-filter proc tq-filter)
+      (setcar c t))))
 
 (defsubst geiser-con--connection-process (c)
   (tq-process (cdr (assoc :tq c))))
 
+(defsubst geiser-con--connection-filter (c)
+  (cdr (assoc :filter c)))
+
+(defsubst geiser-con--connection-tq-filter (c)
+  (cdr (assoc :tq-filter c)))
+
 (defsubst geiser-con--connection-tq (c)
   (cdr (assoc :tq c)))
 
@@ -164,7 +175,8 @@
         `((error (key . geiser-debugger))
           (output . ,answer))
       (condition-case err
-          (car (read-from-string answer))
+          (let ((form (car (read-from-string answer))))
+            (and (listp form) form))
         (error `((error (key . geiser-con-error))
                  (output . ,(format "%s\n(%s)"
                                     answer
@@ -192,6 +204,7 @@
   (geiser-log--info "REQUEST: <%s>: %s"
                     (geiser-con--request-id r)
                     (geiser-con--request-string r))
+  (geiser-con--connection-activate c)
   (tq-enqueue (geiser-con--connection-tq c)
               (concat (geiser-con--request-string r) "\n")
               (geiser-con--connection-eot c)