Tracking when variables get updated

Question

I have a problem with org-mode's agenda view. While I've set org-agenda-files to '("~/org/") invariably when I finally spin up M-x org-agenda I find that org-agenda-files just points to one org-file. Obviously something is deciding just to include the last org-file I viewed but I'm having trouble working out what. Is there any way to trap when this variable is changed and display or log some sort of backtrace?

Answer 1

In this situation, I find that the best way to figure out what's going on into is to visit my ~/.emacs.d/ and run rgrep.

Searching your configs

The following snippet, taken from here, makes sure that rgrep doesn't go into the elpa/ subdir (since you're sure to find dozens of useless hits in there).

(eval-after-load 'grep
  '(progn
     (add-to-list 'grep-find-ignored-directories "auto")
     (add-to-list 'grep-find-ignored-directories "elpa")))

Then I just run

M-x rgrep RET org-agenda-files RET *.el RET ~/.emacs.d/

which will find any reference to org-agenda-files in my configuration. If it's a problem with my configs, this will find it.

Searching Elsewhere

If the above doesn't find anything, it means there's an Elpa package causing trouble. So I do

M-x rgrep RET org-agenda-files RET *.el RET ~/.emacs.d/elpa/

This will usually yield a lot of results, but there are ways to go through them quickly. For instance, it's very unlikely that org-mode itself is causing this problem. So it's safe to ignore all hits that come from inside org-modes installation directory.

Answer 2

Another option you have is to track the value of this variable throughout the execution of org-agenda, that has to tell you where the problem is.

1. Evaluate the following code:

   (global-set-key [f1] (lambda () (interactive) (message "%s" org-agenda-files)))
   

2. Visit the function with M-x find-function RET org-agenda.

3. Edebug it with C-u C-M-x.
4. Call the function, M-x org-agenda.
5. Gradually step through it by pressing n, and monitor the value of the variable by hitting F1.

At some point inside the org-agenda function, you'll hit F1 and the value of org-agenda-files will have changed. That will tell you where to look.

Answer 3

Since 26.1, you can use add-variable-watcher to track the variable where and how be changed.

 Function: add-variable-watcher symbol watch-function

Because the watch-function will be called with 4 arguments: symbol, newval, operation, and where, you can simply add a watcher in your init.el, for example,

(add-variable-watcher 'tab-width (lambda (&rest x) (message "Oops! tab-width changed: %S" x)))

which gives you some messages like

Oops! tab-width changed: (tab-width 2 set #<buffer xxx.el>)

Answer 4

Are you ever using C-c [ (org-agenda-file-to-front) or C-c ] (org-remove-file) while in an org file?

These overwrite the current org-agenda-files with a hardcoded list of files that will no longer use your defined ~/org/ as a source.

Also if you are setting it to ~/org/ please ensure that the agenda files you want are in that folder with .org for the extension. Otherwise they will not be detected.