Super User is a question and answer site for computer enthusiasts and power users. It only takes a minute to sign up.
Sign up to join this community
When I open an empty haskell file, which activates haskell-mode, I get the message
user-error: No items suitable for an index found in this buffer
If I do the same thing, but call toggle-debug-on-error beforehand, I get the same message: it doesn't enter the debugger when user-error is signalled.
How do I make emacs enter the debugger on user-error?
Good question! The answer is to remove user-error from option debug-ignored-errors. M-x customize-option debug-ignored-errors, and remove the entry for user-error.
However, IMO the Emacs manual should be transparent about this, and it is not. Even the Elisp manual is not clear about this -- the only hint is this mention in passing, within the description of option debug-ignored-errors:
The normal value of this variable includes
user-error', as well as several errors that happen often during editing but rarely result from bugs in Lisp programs. However, "rarely" is not "never"; if your program fails with an error that matches this list, you may try changing this list to debug the error. The easiest way is usually to setdebug-ignored-errors' to `nil'.
FWIW, I've submitted Emacs bug #18005 for the missing doc.
