1 ;;; bug-hunter.el --- Hunt down errors in elisp files -*- lexical-binding: t; -*-
3 ;; Copyright (C) 2015 Free Software Foundation, Inc.
5 ;; Author: Artur Malabarba <bruce.connor.am@gmail.com>
6 ;; URL: http://github.com/Bruce-Connor/elisp-bug-hunter
9 ;; Package-Requires: ((seq "1.3") (cl-lib "0.5"))
11 ;; This program is free software; you can redistribute it and/or modify
12 ;; it under the terms of the GNU General Public License as published by
13 ;; the Free Software Foundation, either version 3 of the License, or
14 ;; (at your option) any later version.
16 ;; This program is distributed in the hope that it will be useful,
17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 ;; GNU General Public License for more details.
21 ;; You should have received a copy of the GNU General Public License
22 ;; along with this program. If not, see <http://www.gnu.org/licenses/>.
25 ;; `bug-hunter' is an Emacs library that finds the source of an error or
26 ;; unexpected behavior inside an elisp configuration file (tipically
27 ;; `init.el' or `.emacs').
33 ;; If your Emacs init file signals an error during startup, but you don’t
34 ;; know why, simply issue
36 ;; | M-x bug-hunter-init-file RET RET
38 ;; and `bug-hunter' will find it for you.
40 ;; If Emacs starts up without errors but something is not working as it
41 ;; should, invoke the same command, but give it in an assertion.
42 ;; Essentially, if you can write a snippet that detects the issue and
43 ;; returns non-nil, just provide this snippet as the assertion and the
44 ;; Bug Hunter will do a bisection search for you.
46 ;; For example, let’s say there’s something in your init file that’s
47 ;; loading the `cl' library, and you don’t want that. You /know/ you’re
48 ;; not loading it yourself, but how can you figure out which external
49 ;; package is responsible for this outrage?
52 ;; | M-x bug-hunter-init-file RET (featurep 'cl) RET
55 ;; *That’s it!* You’ll be given a nice buffer reporting the results:
57 ;; - Are you getting obscure errors when trying to open /“.tex”/ files?
58 ;; Don’t despair! Just use `(find-file "dummy.tex")' as the assertion.
59 ;; - Did `ox-html' stop working due to some arcane misconfiguration? Just
60 ;; write an assertion that does an export and checks the result.
61 ;; - Does some random command suddenly bind itself to `C-j' and you can’t
62 ;; figure out why? `(eq (key-binding "\n") 'unwanted-command)' is the
65 ;; Finally, you can also use `bug-hunter-file' to hunt in other files.
71 ;; Bug Hunter will be on Gelpa shortly. For now, do the following:
72 ;; 1. Open the `bug-hunter.el` file.
73 ;; 2. Issue `M-x package-install-from-buffer`.
80 (defvar bug-hunter--assertion-reminder
81 "Remember, the assertion must be an expression that returns
82 non-nil in your current (problematic) Emacs state, AND that
83 returns nil on a clean Emacs instance."
84 "Printed to the user if they provide a bad assertion.")
86 (defvar bug-hunter--current-head nil
87 "Current list of expressions under scrutiny. Used for user feedback.
88 Used if the user aborts before bisection ends.")
90 (defvar bug-hunter--i 0
91 "Current step of the bisection. Used for user feedback.")
92 (defvar bug-hunter--estimate 0
93 "Estimate on how many steps the bisection can take. Used for user feedback.
94 This is the base 2 log of the number of expressions in the
97 (defvar bug-hunter--current-file nil
98 "File currently being debugged.")
100 (defun bug-hunter--read-buffer ()
101 "Return all sexps after point as a list."
103 (or (condition-case er
104 ;; Looks hacky, but comes from `byte-compile-from-buffer'.
105 (while (progn (while (progn (skip-chars-forward " \t\n\^l")
109 (setq line (line-number-at-pos (point)))
110 (setq col (current-column))
111 (push (list (read (current-buffer)) line col)
114 (end-of-file `(bug-caught (end-of-file) ,line ,col))
115 (invalid-read-syntax `(bug-caught ,er ,line ,col))
116 (error (error "Ran into an error we don't understand, please file a bug report: %S" er)))
119 (defun bug-hunter--read-contents (file)
120 "Return all sexps in FILE as a list."
122 (insert-file-contents file)
123 (goto-char (point-min))
124 (bug-hunter--read-buffer)))
127 ;;; Reporting functions
128 (defun bug-hunter--report-print (&rest r)
129 "Print information on the \"*Bug-Hunter Report*\" buffer.
130 R is passed to `format' and inserted."
131 (with-current-buffer (get-buffer-create "*Bug-Hunter Report*")
132 (goto-char (point-max))
133 (let ((inhibit-read-only t))
134 (insert "\n" (apply #'format r)))))
136 (defun bug-hunter--report (&rest r)
137 "Report arbitrary information.
138 R is passed to `bug-hunter--report-print'."
140 (apply #'bug-hunter--report-print r)
143 (defun bug-hunter--report-user-error (&rest r)
144 "Report the user has done something wrong.
145 R is passed to `bug-hunter--report-print'."
147 (apply #'bug-hunter--report-print r)
148 (bug-hunter--report-print "\xc")
149 (apply #'user-error r))
151 (defvar compilation-error-regexp-alist)
152 (defun bug-hunter--init-report-buffer ()
153 "Create and prepare the \"*Bug-Hunter Report*\" buffer."
154 (or (get-buffer "*Bug-Hunter Report*")
155 (with-current-buffer (get-buffer-create "*Bug-Hunter Report*")
156 (compilation-mode "Bug Hunt")
157 (set (make-local-variable 'compilation-error-regexp-alist)
161 (defun bug-hunter--pretty-format (value padding)
162 "Return a VALUE as a string with PADDING spaces on the left."
164 (pp value (current-buffer))
165 (goto-char (point-min))
166 (let ((pad (make-string padding ?\s)))
172 (defun bug-hunter--report-error (error line column &optional expression)
173 "Print on report buffer information about ERROR.
174 LINE and COLUMN are the coordinates where EXPRESSION started in
177 (bug-hunter--report "%S, line %s pos %s:"
178 bug-hunter--current-file line column))
179 (bug-hunter--report " %s"
182 "There's a missing closing parenthesis, the expression on this line never ends.")
184 (let ((char (cadr error)))
185 (if (member char '("]" ")"))
186 (concat "There's an extra " char
187 " on this position. There's probably a missing "
188 (if (string= char ")") "(" "[")
190 (concat "There's a " char
191 " on this position, and that is not valid elisp syntax."))))
193 (let* ((print-level 2)
196 (size (length forms)))
197 (concat "User aborted while testing the following expressions:\n"
198 (mapconcat (lambda (x) (bug-hunter--pretty-format x 4))
199 (if (< size 16) forms (seq-take forms 7))
202 (format "\n ... %s omitted expressions ...\n\n"
205 (mapconcat (lambda (x) (bug-hunter--pretty-format x 4))
206 (seq-drop forms (- size 7)) "")))))
208 (concat "The assertion returned the following value here:\n"
209 (bug-hunter--pretty-format (cadr error) 4)))
210 (t (format "The following error was signaled here:\n %S"
213 (bug-hunter--report " Caused by the following expression:\n%s"
214 (bug-hunter--pretty-format expression 4)))
215 (bug-hunter--report "\xc")
216 `[,error ,line ,column ,expression])
219 ;;; Execution functions
220 (defun bug-hunter--run-form (form)
221 "Run FORM with \"emacs -Q\" and return the result."
222 (let ((out-buf (generate-new-buffer "*Bug-Hunter Command*"))
223 (exec (file-truename (expand-file-name invocation-name
224 invocation-directory)))
225 (file-name (make-temp-file "bug-hunter")))
227 (let ((print-length nil)
229 (with-temp-file file-name
230 (print (list 'prin1 form) (current-buffer)))
231 (call-process exec nil out-buf nil
233 (shell-quote-argument file-name))
234 (with-current-buffer out-buf
235 (goto-char (point-max))
237 (prog1 (read (current-buffer))
238 (kill-buffer (current-buffer)))))
239 (delete-file file-name))))
241 (defun bug-hunter--run-and-test (forms assertion)
242 "Execute FORMS in the background and test ASSERTION.
243 See `bug-hunter' for a description on the ASSERTION."
244 (bug-hunter--run-form
246 (let ((server-name (make-temp-file "bug-hunter-temp-server-file")))
247 (delete-file server-name)
249 (run-hooks 'after-init-hook)
251 (error (cons 'bug-caught er)))))
255 ;;; The actual bisection
256 (defun bug-hunter--split (l)
257 "Split list L in two lists of same size."
258 (seq-partition l (ceiling (/ (length l) 2.0))))
260 (defun bug-hunter--bisect (assertion safe head &optional tail)
261 "Implementation used by `bug-hunter--bisect-start'.
262 ASSERTION is received by `bug-hunter--bisect-start'.
263 SAFE is a list of forms confirmed to not match the ASSERTION,
264 HEAD is a list of forms to be tested now, and TAIL is a list
265 which will be inspected if HEAD doesn't match ASSERTION."
268 (vector (length safe)
269 ;; Sometimes we already ran this, sometimes not. So it's
270 ;; easier to just run it anyway to get the return value.
271 (bug-hunter--run-and-test (append safe head) assertion)))
272 ((and (message "Testing: %s/%s"
273 (cl-incf bug-hunter--i)
274 bug-hunter--estimate)
275 (setq bug-hunter--current-head head)
276 (bug-hunter--run-and-test (append safe head) assertion))
277 (apply #'bug-hunter--bisect
280 (bug-hunter--split head)))
281 (t (apply #'bug-hunter--bisect
284 (bug-hunter--split tail)))))
286 (defun bug-hunter--bisect-start (forms assertion)
287 "Run a bisection search on list of FORMS using ASSERTION.
288 Returns a vector [n value], where n is the position of the first
289 element in FORMS which trigger ASSERTION, and value is the
290 ASSERTION's return value.
292 If ASSERTION is nil, n is the position of the first form to
293 signal an error and value is (bug-caught . ERROR-SIGNALED)."
294 (let ((bug-hunter--i 0)
295 (bug-hunter--estimate (ceiling (log (length forms) 2)))
296 (bug-hunter--current-head nil))
297 (condition-case-unless-debug nil
298 (apply #'bug-hunter--bisect assertion nil (bug-hunter--split forms))
299 (quit `[nil (bug-caught user-aborted ,bug-hunter--current-head)]))))
303 (defun bug-hunter-hunt (rich-forms assertion)
304 "Bisect RICH-FORMS using ASSERTION.
305 RICH-FORMS is a list with elements of the form: (EXPR LINE COL)
306 EXPR is an elisp expression. LINE and COL are the coordinates
307 in `bug-hunter--current-file' where the expression starts.
308 It is expected that one of EXPR is either throwing an error or
309 causing some undesirable effect (which triggers ASSERTION).
311 ASSERTION is either nil or an expression.
312 If nil, EXPRs are bisected until we find the first one that
314 If it is an expression, EXPRs are bisected by testing
315 ASSERTION. It should return nil if all is fine (e.g. if used
316 with \"emacs -Q\"), and should return non-nil when a problem
319 Bug hunter will refuse to hunt if (i) an error is signaled or the
320 assertion is triggered while running emacs -Q, or (ii) no errors
321 are signaled and the assertion is not triggered after all EXPRs
323 (pop-to-buffer (bug-hunter--init-report-buffer))
324 (let ((expressions (unless (eq (car-safe rich-forms) 'bug-caught)
325 (mapcar #'car rich-forms))))
328 (apply #'bug-hunter--report-error (cdr rich-forms))
329 (apply #'vector (cdr rich-forms)))
331 ;; Make sure there's a bug to hunt.
332 ((progn (bug-hunter--report "Doing some initial tests...")
333 (not (bug-hunter--run-and-test expressions assertion)))
334 (bug-hunter--report-user-error "Test failed.\n%s\n%s"
336 (concat "The assertion returned nil after loading the entire file.\n"
337 bug-hunter--assertion-reminder)
338 "No errors signaled after loading the entire file. If you're
339 looking for something that's not an error, you need to provide an
340 assertion. See this link for some examples:
341 https://github.com/Bruce-Connor/elisp-bug-hunter")
344 ;; Make sure we're in a forest, not a volcano.
345 ((bug-hunter--run-and-test nil assertion)
346 (bug-hunter--report-user-error "Test failed.\n%s\n%s"
348 (concat "Assertion returned non-nil even on emacs -Q:"
349 bug-hunter--assertion-reminder)
350 "Detected a signaled error even on emacs -Q. I'm sorry, but there
351 is something seriously wrong with your Emacs installation.
352 There's nothing more I can do here.")
356 ;; Perform the actual hunt.
357 (bug-hunter--report "Initial tests done. Hunting for the cause...")
358 (let* ((result (bug-hunter--bisect-start expressions assertion)))
360 (bug-hunter--report-user-error "No problem was found, despite our initial tests.\n%s"
361 "I have no idea what's going on.")
362 (let* ((pos (elt result 0))
364 (linecol (when pos (cdr (elt rich-forms pos))))
365 (expression (when pos (elt expressions pos))))
366 (if (eq (car-safe ret) 'bug-caught)
367 (bug-hunter--report-error
368 (cdr ret) (car linecol) (cadr linecol) expression)
369 (bug-hunter--report-error
370 (list 'assertion-triggered ret)
371 (car linecol) (cadr linecol) expression)))))))))
373 (defun bug-hunter--read-from-minibuffer ()
374 "Read a list of expressions from the minibuffer.
375 Wraps them in a progn if necessary."
379 ;; Copied from `read--expression'.
380 (let ((minibuffer-completing-symbol t))
381 (minibuffer-with-setup-hook
383 ;; FIXME: call emacs-lisp-mode?
384 (add-function :before-until (local 'eldoc-documentation-function)
385 #'elisp-eldoc-documentation-function)
386 (add-hook 'completion-at-point-functions
387 #'elisp-completion-at-point nil t)
388 (run-hooks 'eval-expression-minibuffer-setup-hook))
390 (read-from-minibuffer
391 "Expression that returns nil if all is well (optional): "
392 nil read-expression-map nil 'read-expression-history))))
393 (goto-char (point-min))
394 (mapcar #'car (bug-hunter--read-buffer)))))
400 (defun bug-hunter-file (file &optional assertion)
401 "Bisect FILE while testing ASSERTION.
402 All sexps in FILE are read and passed to `bug-hunter-hunt' as a
403 list. See `bug-hunter-hunt' for how to use assertion."
406 (read-file-name "File to bisect: "
407 (file-name-directory (or (buffer-file-name) "./"))
409 (file-name-nondirectory (or (buffer-file-name) "./")))
410 (bug-hunter--read-from-minibuffer)))
411 (let ((bug-hunter--current-file file))
412 (bug-hunter-hunt (bug-hunter--read-contents file) assertion)))
415 (defun bug-hunter-init-file (&optional assertion)
416 "Test ASSERTION throughout `user-init-file'.
417 All sexps inside `user-init-file' are read and passed to
418 `bug-hunter-hunt' as a list. See `bug-hunter-hunt' for how to use
420 (interactive (list (bug-hunter--read-from-minibuffer)))
421 (bug-hunter-file user-init-file assertion))
423 (provide 'bug-hunter)
424 ;;; bug-hunter.el ends here