The Bug Hunter

The Bug Hunter is an Emacs library that finds the source of an error or unexpected behavior inside an elisp configuration file (tipically init.el or .emacs).

Usage Examples

If your Emacs init file signals an error during startup, but you don’t know why, simply issue

M-x bug-hunter-init-file RET RET

and The Bug Hunter will find it for you.

If Emacs starts up without errors but something is not working as it should, invoke the same command, but give it in an assertion. Essentially, if you can write a snippet that detects the issue and returns non-nil, just provide this snippet as the assertion and the Bug Hunter will do a bisection search for you.

For example, let’s say there’s something in your init file that’s loading the cl library, and you don’t want that. You know you’re not loading it yourself, but how can you figure out which external package is responsible for this outrage?

M-x bug-hunter-init-file RET (featurep 'cl) RET

That’s it! You’ll be given a nice buffer reporting the results:

• Are you getting obscure errors when trying to open “.tex” files?
  • Don’t despair! Just use (find-file "dummy.tex") as the assertion.
• Did ox-html stop working due to some arcane misconfiguration?
  • Just write an assertion that does an export and checks the result.
• Does some random command suddenly bind itself to C-j and you can’t figure out why?
  • (eq (key-binding "\n") 'unwanted-command) is the assertion for you!

Finally, you can also use bug-hunter-file to hunt in other files.

Installation

The Bug Hunter is available from GNU Elpa to all Emacs versions since 24.1. To install, just issue

M-x package-install RET bug-hunter