To install this package, run in Emacs:
M-x package-install RET bug-hunter RET
#+OPTIONS: toc:nil num:nil #+TITLE: [[file:hunter.png]] The Bug Hunter [[https://travis-ci.org/Malabarba/elisp-bug-hunter][file:https://travis-ci.org/Malabarba/elisp-bug-hunter.svg?branch=master]] /Automatically debug and bisect your init (.emacs) file!/ The Bug Hunter is an Emacs library that finds the source of an error or unexpected behavior inside an elisp configuration file (typically ~init.el~ or ~.emacs~). [[file:hunter-screencast.gif]] * Usage Examples ** Automated error hunting If your Emacs init file signals an error during startup, but you don’t know why, simply issue #+BEGIN_SRC text M-x bug-hunter-init-file RET e #+END_SRC and The Bug Hunter will find it for you. Note that your ~init.el~ (or ~.emacs~) must be idempotent for this to work. ** Interactive hunt If Emacs starts up without errors but something is not working as it should, invoke the same command, but choose the interactive option: #+BEGIN_SRC text M-x bug-hunter-init-file RET i #+END_SRC The Bug Hunter will start a separate Emacs instance several times, and then it will ask you each time whether that instance presented the problem you have. After doing this about 5--12 times, you’ll be given the results. ** Assertion hunt The Bug Hunter can also find your issue based on an assertion. Essentially, if you can write a code snippet that returns non-nil when it detects the issue, just provide this snippet as the assertion and the Bug Hunter will do the rest. 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? #+BEGIN_SRC text M-x bug-hunter-init-file RET a (featurep 'cl) RET #+END_SRC *That’s it!* You’ll be given a nice buffer reporting the results: [[file:cl-example.png]] - 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 [[https://elpa.gnu.org/packages/bug-hunter.html][GNU Elpa]] to all Emacs versions since ~24.1~. To install, just issue #+BEGIN_SRC text M-x package-install RET bug-hunter #+END_SRC * init.org and other literate-style configs Some people (me included) like to organize their init files by writting it in ~org-mode~ instead of Emacs-Lisp. This usually involves adding something like this to ~init.el~, #+BEGIN_SRC emacs-lisp ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ;;; Maybe some code up here ;;; ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (require 'org) (org-babel-tangle-file "~/.emacs.d/org-init.org" "~/.emacs.d/org-init.el") (load "~/.emacs.d/org-init.el") #+END_SRC At first, this makes the Bug-Hunter essentially useless, for it will do the hunting in ~init.el~ instead of the much more extensive ~org-init.el~. The name of the second file (~org-init.el~) will vary, but the point is the same. But fear not! There’s a simple solution: 1. If you have any code above the call to ~org-babel-tangle-file~, copy that to the top of ~org-init.el~ (or whatever is the name of your tangled file). This includes that ~(require 'org)~ over there. 2. Invoke ~M-x~ ~bug-hunter-file~ (instead of ~bug-hunter-init-file~). It will ask you which file to debug, and you need to point it to your tangled output file ~org-init.el~.