综合以前几篇关于etags的blog,并添加了一点新的内容,拼凑出了一篇etags guide,欢迎批评指正。
etags
让find-tag首先定位当前buffer的tag
find-tag
定位tag受到很多因素的影响,有时候希望它能首先定位到当前buffer的tag,但是它却跳到其它地方去了。如http://debbugs.gnu.org/cgi/bugreport.cgi?bug=2544描述的static
函数是一个例子,另外就是为不同体系结构或者操作系统实现接口时使用相同的名字。如果我们注意到这种情况,那么只是操作上麻烦一点,倒还好说;如果没注意到,那么可能完全读错了代码,我在读Android Dalvik garbage collection的实现时就吃到了苦头。
为了解决这个问题,我对find-tag
做了一点小小的改进,使其首先定位当前buffer的tag,这样就不会造成困惑。
方法很简单,首先从etags.el
从复制出三个函数:find-tag
、find-tag-noselect
、以及find-tag-in-order
,然后把他们重新命名为wl-etags-find-tag
、wl-etags-find-tag-noselect
和wl-etags-find-tag-in-order
,并修改相应的调用点。最后把wl-etags-find-tag-in-order
修改为下面的样子:
(defun wl-etags-get-from-buffer-file-name () (let ((marker (ring-ref find-tag-marker-ring 0))) (with-current-buffer (marker-buffer marker) buffer-file-name))) (defun wl-etags-goto-file (file) (let (beg) (while (and (search-forward "\f\n" nil t) (progn (setq beg (point)) (end-of-line) (skip-chars-backward "^," beg) (or (looking-at "include$") (not (string-equal file (expand-file-name (convert-standard-filename (buffer-substring beg (1- (point))))))))))))) ;;; prefer tag in the same buffer as source buffer (defun wl-etags-find-tag-in-order (pattern search-forward-func order next-line-after-failure-p matching first-search) "Internal tag-finding function. PATTERN is a string to pass to arg SEARCH-FORWARD-FUNC, and to any member of the function list ORDER. If ORDER is nil, use saved state to continue a previous search. Arg NEXT-LINE-AFTER-FAILURE-P is non-nil if after a failed match, point should be moved to the next line. Arg MATCHING is a string, an English `-ing' word, to be used in an error message." ;; Algorithm is as follows: ;; For each qualifier-func in ORDER, go to beginning of tags file, and ;; perform inner loop: for each naive match for PATTERN found using ;; SEARCH-FORWARD-FUNC, qualify the naive match using qualifier-func. If ;; it qualifies, go to the specified line in the specified source file ;; and return. Qualified matches are remembered to avoid repetition. ;; State is saved so that the loop can be continued. (let (file ;name of file containing tag tag-info ;where to find the tag in FILE (first-table t) (tag-order order) (match-marker (make-marker)) goto-func (case-fold-search (if (memq tags-case-fold-search '(nil t)) tags-case-fold-search case-fold-search)) ) (save-excursion (if first-search ;; This is the start of a search for a fresh tag. ;; Clear the list of tags matched by the previous search. ;; find-tag-noselect has already put us in the first tags table ;; buffer before we got called. (setq tag-lines-already-matched nil) ;; Continuing to search for the tag specified last time. ;; tag-lines-already-matched lists locations matched in previous ;; calls so we don't visit the same tag twice if it matches twice ;; during two passes with different qualification predicates. ;; Switch to the current tags table buffer. (visit-tags-table-buffer 'same)) ;; Get a qualified match. (catch 'qualified-match-found ;; Iterate over the list of tags tables. (while (or first-table (visit-tags-table-buffer t)) (and first-search first-table ;; Start at beginning of tags file. (goto-char (point-min))) ;; Iterate over the list of ordering predicates. (while order ;; Only give one chance to tags in the from buffer here. ;; They can be found later. (when (and first-search first-table) (let ((file (wl-etags-get-from-buffer-file-name))) (when file (let* ((file-beg-pos (progn (wl-etags-goto-file file) (beginning-of-line) (point))) (file-end-pos (progn (search-forward "\f\n" nil t) (point)))) (goto-char file-beg-pos) (while (funcall search-forward-func pattern file-end-pos t) ;; Naive match found. Qualify the match. (and (funcall (car order) pattern) ;; Make sure it is not a previous qualified match. (not (member (set-marker match-marker (point-at-bol)) tag-lines-already-matched)) (throw 'qualified-match-found nil)) (if next-line-after-failure-p (forward-line 1))) ;; Nothing found. Restart from the beginning. (goto-char (point-min)))))) (while (funcall search-forward-func pattern nil t) ;; Naive match found. Qualify the match. (and (funcall (car order) pattern) ;; Make sure it is not a previous qualified match. (not (member (set-marker match-marker (point-at-bol)) tag-lines-already-matched)) (throw 'qualified-match-found nil)) (if next-line-after-failure-p (forward-line 1))) ;; Try the next flavor of match. (setq order (cdr order)) (goto-char (point-min))) (setq first-table nil) (setq order tag-order)) ;; We throw out on match, so only get here if there were no matches. ;; Clear out the markers we use to avoid duplicate matches so they ;; don't slow down editing and are immediately available for GC. (while tag-lines-already-matched (set-marker (car tag-lines-already-matched) nil nil) (setq tag-lines-already-matched (cdr tag-lines-already-matched))) (set-marker match-marker nil nil) (error "No %stags %s %s" (if first-search "" "more ") matching pattern)) ;; Found a tag; extract location info. (beginning-of-line) (setq tag-lines-already-matched (cons match-marker tag-lines-already-matched)) ;; Expand the filename, using the tags table buffer's default-directory. ;; We should be able to search for file-name backwards in file-of-tag: ;; the beginning-of-line is ok except when positioned on a "file-name" tag. (setq file (expand-file-name (if (memq (car order) '(tag-exact-file-name-match-p tag-file-name-match-p tag-partial-file-name-match-p)) (save-excursion (forward-line 1) (file-of-tag)) (file-of-tag))) tag-info (funcall snarf-tag-function)) ;; Get the local value in the tags table buffer before switching buffers. (setq goto-func goto-tag-location-function) (tag-find-file-of-tag-noselect file) (widen) (push-mark) (funcall goto-func tag-info) ;; Return the buffer where the tag was found. (current-buffer))))
从实现上来说,并非完美的方案,有值得商榷的地方;从使用上来说,完美解决了我目前碰到的问题。:-)