RE: Eshell - `Text is read-only`

[Drew Adams <drew.adams@oracle.com>]

> > Hi all, I've run into the dreaded `Text is read-only` bug which stops
> > eshell from closing and Emacs from exiting. I got this in a previous
> > version of Emacs and fixed it with the following snippet:
> 
> I just hit the problem today. I'd say it occurs once a month at the
> most.
>
> Although it does not happen frequently, I sure would like to get it
> solved. There's only one solution afaik, and that's just killing emacs,
> as in `kill -9 emacs_pid`. This is drastic, but the only way I know to
> get rid of the buffer :(
> 
> Any suggestion and/or help would be really appreciated!

The standard error that shows that error message is `text-read-only'.
(See (elisp) `Standard Errors'.)

You could try wrapping whatever code you use that ends up calling
calling code that raises the error with this:

(condition-case handle-text-read-only
  ... ; Your code that leads to the error goes here
  (text-read-only (debug)))

That should put you in the debugger whenever that error is raised.
From there you can evaluate expressions (using `e') to possibly
get more info about what the problem (cause) is.

Note that this is a subcategory of standard error `buffer-read-only'.
It arises when something tries to modify a character that has text
property `read-only' (see (elisp) `Text Properties').

You can also just try setting `debug-on-error' to t, in which case
the debugger should be entered for any error.

However you get to the debugger, it provides a backtrace of the
functions that led to the error.  With that knowledge, you can
use `debug-on-entry FUNCTION', to instead enter the debugger for
a FUNCTION you see on the backtrace stack, and then step through
its evaluation using `d'.  That will give you a better idea of
what's going on.