Inferior fsharp tab completion

inf-fsharp-mode.el

@@ -38,7 +38,7 @@
 
 (defvar inferior-fsharp-program
   (if fsharp-ac-using-mono
-      "fsharpi --readline-"
+      "fsharpi"
     (concat "\"" (fsharp-mode--executable-find "fsi.exe") "\" --fsi-server-input-codepage:65001"))
   "*Program name for invoking an inferior fsharp from Emacs.")
 
@@ -48,6 +48,7 @@
 (defvar inferior-fsharp-mode-map
   (let ((map (copy-keymap comint-mode-map)))
     (define-key map [M-return] 'fsharp-comint-send)
+    (define-key map (kbd "<tab>") 'inferior-fsharp-get-completion)
     map))
 
 ;; Augment fsharp mode, so you can process fsharp code in the source files.
@@ -90,7 +91,14 @@ be sent from another buffer in fsharp mode.
 	  (or cmd (read-from-minibuffer "fsharp toplevel to run: "
 					inferior-fsharp-program)))
     (let ((cmdlist (inferior-fsharp-args-to-list inferior-fsharp-program))
-          (process-connection-type nil))
+          ;; fsi (correctly) disables any sort of console interaction if it
+          ;; thinks we're a dumb terminal, and `comint-term-environment'
+          ;; (correctly) defaults to setting TERM=dumb on systems using
+          ;; terminfo, which is basically every modern system.
+          ;;
+          ;; we want to make use of fsi's tab completion, so tell comint
+          ;; to set TERM=emacs for our inferior fsharp process.
+          (comint-terminfo-terminal "emacs"))
       (with-current-buffer (apply (function make-comint)
                                   inferior-fsharp-buffer-subname
                                   (car cmdlist) nil
@@ -101,6 +109,132 @@ be sent from another buffer in fsharp mode.
         (inferior-fsharp-mode))
       (display-buffer inferior-fsharp-buffer-name))))
 
+
+;; the first value returned from our inferior f# process that appears to be a
+;; completion. our filters can end up receiving multiple results that would match
+;; any reasonable regexps, doing this prevents clobbering our match with
+;; confusing-looking values.
+;;
+;; this will hopefully go away as we figure out how to get full completion results
+;; from fsi without the sort of awkward automation we're doing here, but on the
+;; chance that it doesn't we might consider making this buffer-local in the case
+;; that people want to use multiple inferior fsharp buffers in the future.
+(defvar inf-fsharp-completion-match nil)
+
+;; the completion functions below are almost directly ripped from `comint', in
+;; particular the `comint-redirect' functions. since `comint' pretty much
+;; assumes we're line- based, and we cant easily (as far as i know) extend fsi
+;; at runtime to let us retrieve full completion info the way that the
+;; `python-shell-completion-native' functions do, we need to do some extra stuff
+;; to send <tab> and handle deleting input that comint doesn't know has already
+;; been sent to fsi
+
+(defun inf-fsharp-redirect-filter (process input-string)
+  (with-current-buffer (process-buffer process)
+    (unless inf-fsharp-completion-match
+      ;; this if-cascasde doesn't work if we convert it to a cond clause ??
+      (if (and input-string
+               (string-match comint-redirect-finished-regexp input-string))
+          (setq inf-fsharp-completion-match input-string)
+
+        ;; for some reason, we appear to get the results from fsi fontified
+        ;; already in `comint-redirect-previous-input-string' without having
+        ;; them pass through this function as `input-string' even though this
+        ;; function (or comint-redirect-filter when we were using that directly)
+        ;; is the only place we've been able to find that modifies the variable.
+        ;;
+        ;; looks like a race-condition or multithreading issue but not sure.
+        ;; either way, we need to check here to make sure we don't miss our match
+        (if (and comint-redirect-previous-input-string
+                 (string-match comint-redirect-finished-regexp
+                               (concat comint-redirect-previous-input-string input-string)))
+            (setq inf-fsharp-completion-match
+                  (concat comint-redirect-previous-input-string input-string)))))
+
+    (setq comint-redirect-previous-input-string input-string)
+
+    (if inf-fsharp-completion-match
+        (let ((del-string (make-string (length inf-fsharp-completion-match) ?\b)))
+          ;; fsi thinks we should have completed string that hasn't been sent in
+          ;; the input buffer, but we will actually send later after inserting
+          ;; the fsi-completed string into our repl buffer, so we need to delete
+          ;; the match from fsi's input buffer to avoid sending nonsense strings.
+          (process-send-string process del-string)
+
+          ;; we need to make sure our deletion command goes through before we
+          ;; exit this func and remove our current output-filter otherwise we'll
+          ;; end up with the output from fsi confirming our backspaces in our
+          ;; repl buffer, i.e, if we had "string" we'd see "strin stri str st s
+          ;; ". we'd like to find a better way than sleeping to do this, but
+          ;; there's not really a way for emacs to know that a process is done
+          ;; sending it input as opposed to just not sending it yet....
+          (sleep-for 1)
+
+          (save-excursion
+            (set-buffer comint-redirect-output-buffer)
+            (erase-buffer)
+            (goto-char (point-min))
+            (insert (ansi-color-filter-apply inf-fsharp-completion-match)))
+
+          (comint-redirect-cleanup)
+          (run-hooks 'comint-redirect-hook)))))
+
+(defun inf-fsharp-redirect-get-completion-from-process (input output-buffer process)
+  (let* ((process-buffer (if (processp process)
+                            (process-buffer process)
+                           process))
+         (proc (get-buffer-process process-buffer)))
+
+    (with-current-buffer process-buffer
+      (comint-redirect-setup
+       output-buffer
+       (current-buffer)
+       (concat input "\\(.+\\)")
+       nil)
+
+      (set-process-filter proc #'inf-fsharp-redirect-filter)
+      (process-send-string (current-buffer) (concat input "\t")))))
+
+(defun inf-fsharp-get-completion-from-process (process to-complete)
+  (let ((output-buffer " *inf-fsharp-completion*"))
+    (with-current-buffer (get-buffer-create output-buffer)
+      (erase-buffer)
+      (inf-fsharp-redirect-get-completion-from-process to-complete output-buffer process)
+
+      (set-buffer (process-buffer process))
+      (while (and (null comint-redirect-completed)
+                  (accept-process-output process)))
+
+      (set-buffer output-buffer)
+      (buffer-substring-no-properties (point-min) (point-max)))))
+
+(defun inferior-fsharp-get-completion ()
+  (interactive)
+  (let* ((inf-proc (get-process inferior-fsharp-buffer-subname))
+        (orig-filter (process-filter inf-proc)))
+
+    ;; reset our global completion match marker every time we start a completion
+    ;; search so we don't accidentally use old complete data.
+    (setq inf-fsharp-completion-match nil)
+
+    (with-current-buffer (process-buffer inf-proc)
+      (let* ((pos (marker-position (cdr comint-last-prompt)))
+             (input (buffer-substring-no-properties pos (point))))
+
+        ;; we get the whole of our input back from fsi in the response to our
+        ;; <tab> completion request, so remove the initial repl input here and
+        ;; replace it with that response.
+        (delete-backward-char (length input))
+
+        (insert (inf-fsharp-get-completion-from-process inf-proc input))))
+
+    ;; we'd prefer to reset this filter closer in the file to where we replace
+    ;; it, but we ran into some issues with setting it too early. try to fix
+    ;; this up when we figure out a nicer way of doing this completion stuff
+    ;; overall.
+    (set-process-filter inf-proc orig-filter)))
+
+
 ;;;###autoload
 (defun run-fsharp (&optional cmd)
   "Run an inferior fsharp process.