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A few functions to let me manage TAGS files more easily. Typically, my projects contain at least one sub-folder. I got sick of manually updating tag files, so I wrote this to help me update a single TAGS file per project (always in the projects' root directory).

A few functions to let me manage TAGS files more easily. Typically, my projects contain at least one sub-folder. I got sick of manually updating, so I wrote this to help me update a single TAGS file per project (always in the projects' root directory).

(defun create-tag-table ()
  "This will recursively tag all files of a given type starting with the current buffers' directory. 
   It overwrites the old TAGS file, if one exists. 
   Haskell files assume you've installed `hasktags`."
  (interactive)
  (let ((file-type (get-taggable-extension))
    (cur-dir default-directory)
    (tags-file (find-parent-tags default-directory)))
    (if (equalp file-type "hs")
        (shell-command "hasktags --ignore-close-implementation --etags `find . -type f -name \"*.*hs\"`")
          (shell-command (concat "find -name \"*." file-type "\" -print | etags -")))))

(defun find-parent-tags (dir)
  "Traverses the directory tree up to /home/[user]/ or / whichever comes first. 
   Returns either nil or the directory containing the first TAGS file it finds."
  (interactive (list default-directory))
  (find-parent-tags-rec (build-tag-paths dir)))

(defun find-parent-tags-rec (list-of-filepath)
  (cond ((null list-of-filepath) nil)
    ((file-exists-p (car list-of-filepath)) (car list-of-filepath))
    (t (find-parent-tags-rec (cdr list-of-filepath)))))

(defun build-tag-paths (dir-string)
  (build-tag-paths-rec (remove-if #'empty-string? (split-string dir-string "/")) (list "/")))

(defun build-tag-paths-rec (steps acc)
  (if (null steps) 
      (mapcar (lambda (p) (concat p "TAGS")) acc)
    (build-tag-paths-rec (cdr steps)
             (cons (concat (car acc) (car steps) "/") acc))))

(defun get-taggable-extension ()
  "Either returns the current file's extension (if it's appropriate) or asks the user to pick one with completion"
  (let ((b-name (buffer-file-name (current-buffer)))
    (valid-exts (list "lisp" "py" "c" "hs" "rb" "ss" "scm" "js" "erl" "el")))
    (string-match "\\.\\(.*?\\)$" b-name)
    (let ((current-filetype (match-string 1 b-name)))
      (if (member current-filetype valid-exts)
      current-filetype
    (completing-read "File type: " valid-exts nil 'confirm)))))

(defun empty-string? (s) (equalp s ""))

(provide 'tagariffic)

(defun create-tag-table ()
  "This will recursively tag all files of a given type starting with the current buffers' directory. 
   It overwrites the old TAGS file, if one exists. 
   Haskell files assume you've installed `hasktags`."
  (interactive)
  (let ((file-type (get-taggable-extension))
        (cur-dir default-directory)
        (tags-file (find-parent-tags default-directory)))
    (if (equalp file-type "hs")
        (shell-command "hasktags --ignore-close-implementation --etags `find . -type f -name \"*.*hs\"`")
          (shell-command (concat "find -name \"*." file-type "\" -print | etags -")))))

(defun find-parent-tags (dir)
  "Traverses the directory tree up to /home/[user]/ or / whichever comes first. 
   Returns either nil or the directory containing the first TAGS file it finds."
  (interactive (list default-directory))
  (find-parent-tags-rec (build-tag-paths dir)))

(defun find-parent-tags-rec (list-of-filepath)
  (cond ((null list-of-filepath) nil)
        ((file-exists-p (car list-of-filepath)) (car list-of-filepath))
        (t (find-parent-tags-rec (cdr list-of-filepath)))))

(defun build-tag-paths (dir-string)
  (build-tag-paths-rec (remove-if #'empty-string? (split-string dir-string "/")) (list "/")))

(defun build-tag-paths-rec (steps acc)
  (if (null steps) 
      (mapcar (lambda (p) (concat p "TAGS")) acc)
    (build-tag-paths-rec (cdr steps)
             (cons (concat (car acc) (car steps) "/") acc))))

(defun get-taggable-extension ()
  "Either returns the current file's extension (if it's appropriate) or asks the user to pick one with completion"
  (let ((b-name (buffer-file-name (current-buffer)))
        (valid-exts (list "lisp" "py" "c" "hs" "rb" "ss" "scm" "js" "erl" "el")))
    (string-match "\\.\\(.*?\\)$" b-name)
    (let ((current-filetype (match-string 1 b-name)))
      (if (member current-filetype valid-exts)
          current-filetype
        (completing-read "File type: " valid-exts nil 'confirm)))))

(defun empty-string? (s) (equalp s ""))

(provide 'tagariffic)