Racket: Lack of debug message coming from Emacs with Geiser

Question

I am newbie to use emacs with geiser. Currently, I do not have any problem with its regular operations, such as compiling program or launching REPL. But I do not know why the REPL within Geiser only provides very limited information if my program goes wrong.

For example, I use a mutable list but accidentally use assoc rather than massoc, the error message from REPL in Geiser is

install-deriv-package: undefined;
cannot reference undefined identifier
  context...:
   /Applications/Racket v6.0.1/collects/racket/private/misc.rkt:87:7

However, in the REPL of DrRacket, the error message would be more enlightening:

assoc: not a proper list: (mcons (mcons 'deriv (mcons (mcons '** #<procedure:deriv-
exponential>) (mcons (mcons '* #<procedure:deriv-product>) (mcons (mcons '+ #
<procedure:deriv-sum>) '())))) '())

For the former case, I do not even know where the mistake is.

Is it relevant with the configuration of Geiser? If so, how can I make the error message similar to the one in DrRacket?

Answer 1

Correct me if I'm wrong, but your particular issue seems to be a problem with install-deriv-package being undefined in your Geiser environment, but not being undefined in your DrRacket environment. In any case, it seems to me that the messages generated in the Geiser REPL, geiser-compile-file output, and DrRacket output are quite similar (at least in the case of using assoc rather than massoc on a mutable list):

Geiser REPL error:

racket@> (assoc 3 (mlist (mlist 1 2) (mlist 3 4) (mlist 5 6)))
assoc: not a proper list: (mcons (mcons 1 (mcons 2)) (mcons (mcons 3 (mcons 4)) (mcons (mcons 5 (mcons 6)))))
  context...:
   /Applications/Racket v6.5/collects/racket/private/misc.rkt:87:7

Geiser REPL w/out error:

racket@> (massoc 3 (mlist (mlist 1 2) (mlist 3 4) (mlist 5 6)))
(mcons 3 (mcons 4 '()))

geiser-compile-file error:

Compiling ~/development/lisp/racket/error_testing.rkt ...


Error: struct:exn:fail:contract <- THIS TEXT IS ACTUALLY LINKED TO THE GEISER DOCS PAGE

assoc: not a proper list: (mcons (mcons 1 (mcons 2)) (mcons (mcons 3 (mcons 4)) (mcons (mcons 5 (mcons 6)))))

geiser-compile-file w/out error:

Compiling ~/development/lisp/racket/error_testing.rkt ...


(mcons 3 (mcons 4 '()))

DrRacket error:

(assoc 3 (mlist (mlist 1 2) (mlist 3 4) (mlist 5 6)))
. . assoc: not a proper list: (mcons (mcons 1 (mcons 2 '())) (mcons (mcons 3 (mcons 4 '())) (mcons (mcons 5 (mcons 6 '())) '())))

DrRacket w/out error:

(mcons 3 (mcons 4 '()))

As you can see, all of these outputs seem rather similar. However, to answer your question, I think that geiser-compile-file is the best Geiser option to use here since it gives slightly more information about the error than the Geiser REPL output. Also, the geiser-compile-file buffer defaults to geiser-debug-mode, so that may help with debugging somewhat. Lastly, you may also want to check out this section on the Geiser site.