Hidden dependency on cl

[tburette]

If cl is not loaded, the error message Caught Error: (void-function symbol-macrolet) appears when the server handles a request.

A (require 'cl) must be done somewhere to make the error go away. This dependency is not mentioned anywhere.

Any servlet will trigger the error. For example :

(ws-start                                                                                                                                                                                                                                
 (lambda (request)                                                                                                                                                                   
   (with-slots (process headers) request
     (ws-response-header process 200 '("Content-Type" . "text/plain"))
     (process-send-string process "Hello world\n")))
 9000)

I'm a bit puzzled as I have found no reference to symbol-macrolet. My elisp/emacs skills are too weak to find where the error is coming from.

I'm using the package web-server-20140501.1218 and running emacs 24.3.1

[eschulte]

This problem might be specific to your version of Emacs. With GNU Emacs 24.4.50.2, simply requireing web-server will result in symbol-macrolet being defined (as an alias for cl-symbol-macrolet in cl-lib).

If this is in fact an error, then it is probably an issue with eieio, and should be fixed there. That said if this is biting a lot of people, perhaps it would be worthwhile adding a note to (require 'cl) when this issue is encountered.... I'm just not sure where to add such a warning.

[thesoftwarebin]

My two cents about where to document it: I vote for section REQUIREMENTS in the README file, which I think is shown when you M-x list-packages and select package web-server.

The text could be something like "eieio version: xyz or above; if you have lower versions and get a Caught Error: (void-function symbol-macrolet) then try adding (require 'cl) at start of your file".

[eschulte]

Would it be sufficient to require Emacs 24.4 instead of Emacs 24.3 (eieio is maintained as part of Emacs, so it might no longer have a version seperate from the Emacs version)? This would certainly be simpler.

I guess what I'm asking is, "does upgrading to Emacs 24.4 remove the cl dependency on your systems"?

Thanks,

[eschulte]

Looking at the Emacs commits, it seems this issues in eieio (bug#16998) was fixed March 12th, and the bump to Emacs 24.4 occured March 21st. So changing the requirement from Emacs 24.3 to Emacs 24.4 should be sufficient.

[thesoftwarebin]

The requirement emacs-24.4 is now preventing installation from ELPA to users with emacs 24.3 or older. Package is shown in list-packages but refuses to install. Not a big problem as long as we can download from here, but it's unfortunate that emacs-web-server loses some potential audience.

I just had an :-1: evil thought :-1: : one could trick Emacs 24.3 and install from ELPA anyway, for example by playing with M-x toggle-debug-on-entry RET package-installed-p RET ... :-)

[eschulte]

Emacs 24.4 is in pretest and should be released in the very near future, so this shouldn't be a problem for long.