New synchronous completion function

haskell-completions.el

@@ -37,6 +37,8 @@
 ;;; Code:
 
 (require 'haskell-mode)
+(require 'haskell-process)
+(require 'haskell-interactive-mode)
 
 (defvar haskell-completions-pragma-names
   (list "DEPRECATED"
@@ -219,5 +221,56 @@ result only if prefix length is not less than MINLEN."
              (prefix prefix)))))
 
 
+(defun haskell-completions-sync-completions-at-point ()
+  "A `completion-at-point' function using the current haskell process.
+Returns nil if no completions available."
+  (let ((prefix-data (haskell-completions-grab-prefix)))
+    (when prefix-data
+      (cl-destructuring-bind (beg end pfx typ) prefix-data
+        (let ((imp (eql typ 'haskell-completions-module-name-prefix))
+              lst)
+          (setq lst
+                (cl-case typ
+                  ;; non-interactive completions first
+                  ('haskell-completions-pragma-name-prefix
+                   haskell-completions-pragma-names)
+                  ('haskell-completions-ghc-option-prefix
+                   haskell-ghc-supported-options)
+                  ('haskell-completions-language-extension-prefix
+                   haskell-ghc-supported-extensions)
+                  (otherwise
+                   (when (and
+                          (not (eql typ 'haskell-completions-general-prefix))
+                          (haskell-session-maybe)
+                          (not
+                           (haskell-process-cmd (haskell-interactive-process))))
+                     ;; if REPL is available and not busy try to query it
+                     ;; for completions list in case of module name or
+                     ;; identifier prefixes
+                     (haskell-completions-sync-complete-repl pfx imp)))))
+          (when (or (equal '("") lst)
+                    (eql nil lst))
+            ;; complete things using dabbrev
+            (setq lst (haskell-completions-dabbrev-completions pfx)))
+          (when lst
+            (list beg end lst)))))))
+
+(defun haskell-completions-sync-complete-repl (prefix &optional import)
+  "Return completion list for given PREFIX quering REPL synchronously.
+When optional IMPORT argument is non-nil complete PREFIX
+prepending \"import \" keyword (useful for module names).  This
+function is supposed for internal use."
+  (haskell-process-get-repl-completions
+   (haskell-interactive-process)
+   (if import
+       (concat "import " prefix)
+     prefix)))
+
+(defun haskell-completions-dabbrev-completions (prefix)
+  "Return completion list for PREFIX using dabbrev facility.
+This function is supposed for internal use."
+  (dabbrev--reset-global-variables)
+  (dabbrev--find-all-expansions prefix nil))
+
 (provide 'haskell-completions)
 ;;; haskell-completions.el ends here