compdb.el

;;; package --- Summary

;;; Commentary:

;; You may a hook for flycheck to set flycheck-clang-include-path automatically upon buffer open
;;
;; (add-hook 'flycheck-mode-hook
;;           '(lambda()
;;              (let ((include-path (compdb-get-include-path)))
;;                (when include-path
;;                 (make-local-variable 'flycheck-clang-include-path)
;;                  (setq flycheck-clang-include-path include-path)))))

;;; Code:

(defun compdb-parse (db file)
  "Parse compilation database DB of FILE and return list of include path."
  (when (file-exists-p db)
    (with-temp-buffer
      (insert-file-contents db)
      (goto-char (point-min))
      (let ((end (search-forward file))
            (begin (search-backward "\"command\":")))
        ;; (list begin end)
        (compdb-get-include-path-list begin end)
        ))
    ))

(defun compdb-get-include-path-list (begin end)
  "Parse from BEGIN to END and return list of include path."
  (let ((result nil)
        (current begin))
    (while (and current (< current end))
      (setq current (re-search-forward "-I\\([A-Za-z0-9-_/.]+\\)" end t))
      (if (null result)
          (setq result (list (match-string 1)))
        (add-to-list 'result (match-string 1))))
    result))

;; http://stackoverflow.com/a/1684795/2229134
(defun compdb-find-compdb (dir)
  "Find compilation database starting from DIR."
  (if (file-directory-p dir)
      (append
       (directory-files dir t "compile_commands.json")
       (apply 'append (mapcar 'compdb-find-compdb (directory-files dir t "[^.]+"))))))

(defun compdb-find-compdb-within-depth (dir &optional max-depth depth)
  "Find compilation database from DIR.
Repeat until it find before reaching MAX-DEPTH.
DEPTH is used for recursive call."
  (let ((max-depth (or max-depth 4))
        (depth (or depth 0)))
    (if (> depth max-depth)
        nil
      (or (compdb-find-compdb dir)
          (compdb-find-compdb-within-depth (file-name-directory dir) max-depth (1+ depth))))))

(defun compdb-get-include-path ()
  "Get include-path list from current buffer."
  ;; (let ((db (compdb-find-compdb (file-name-directory (buffer-file-name)))))
  (let* ((max-depth 4)
         (dir (directory-file-name (file-name-directory (buffer-file-name))))
         (db (compdb-find-compdb-within-depth dir max-depth)))
    (when db
      (compdb-parse (car db) (buffer-file-name)))))

;; This hook should be moved to another place.
(add-hook 'flycheck-mode-hook
          '(lambda()
             (let ((include-path (compdb-get-include-path)))
               (when include-path
                 (make-local-variable 'flycheck-clang-include-path)
                 (setq flycheck-clang-include-path include-path)))))

(provide 'compdb)
;;; compdb.el ends here