Define hasktags command composer

Author: geraldus

haskell-cabal.el

@@ -1069,6 +1069,55 @@ source-section."
     ;; unwind
     (haskell-mode-toggle-interactive-prompt-state t)))
 
-(provide 'haskell-cabal)
 
+(defun haskell-cabal--compose-hasktags-command (&optional cabal-dir)
+  "Prepare command to execute hasktags for current file.
+By default following parameters are passed to Hasktags
+executable:
+-e - generate ETAGS file
+-x - generate additional information in CTAGS file.
+
+Tries to find cabal file location, give optional CABAL-DIR
+parameter to override it.  If cabal file not found uses current
+file directory.
+
+This function takes into account user's operation system: in case
+of Windows it generates simple command like
+
+hasktags --output=DIR\TAGS -x -e DIR
+
+relying on Hasktags itself to find source files;
+
+In other cases it uses `find` command to find all source files
+recursively avoiding visiting unnecessary heavy directories like
+.git, .svn, _darcs and build directories created by
+cabal-install, stack, etc."
+  (let ((dir (or cabal-dir
+                 (haskell-cabal-find-dir)
+                 (file-name-directory buffer-file-name))))
+    (when dir
+      (if (eq system-type 'windows-nt)
+          (format "hasktags --output=\"%s\\TAGS\" -x -e \"%s\"" dir dir)
+        (format "cd %s && %s | %s"
+                dir
+                (concat "find . "
+                        "-type d \\( "
+                        "-path ./.git "
+                        "-o -path ./.svn "
+                        "-o -path ./_darcs "
+                        "-o -path ./.stack-work "
+                        "-o -path ./dist "
+                        "-o -path ./.cabal-sandbox "
+                        "\\) -prune "
+                        "-o -type f \\( "
+                        "-name '*.hs' "
+                        "-or -name '*.lhs' "
+                        "-or -name '*.hsc' "
+                        "\\) -not \\( "
+                        "-name '#*' "
+                        "-or -name '.*' "
+                        "\\) -print0")
+                "xargs -0 hasktags -e -x")))))
+
+(provide 'haskell-cabal)
 ;;; haskell-cabal.el ends here