clojure.main/report-error contains a call to pprint which may throw, obscuring the real failure

Mon, 17 Jan 2022 00:01:25 +0000

See the gist: https://gist.github.com/karolinepauls/d5e6398dcfd25e6c2f36abcd6b9eba98

I have produced some preliminary patches, how do I proceed from now? I suppose I need to sign the CA and request a Jira account?

From the gist:

The problem reproduced here occurs when an exception is thrown from
user code and reaches clojure.main code responsible for exception
reporting. Due to the use of pprint, reporting code can fail,
obscuring the error and printing a rather unexpected Java stack trace,
which is probably most obscure in case of StackOverflow.

The root cause is potentially buggy ex-info (ex-data with values
having broken pprint methods or reference cycles, like
https://github.com/overtone/at-at/issues/20) being passed to
Throwable->map in clojure.main/report-error. Throwable->map itself
calls ex-data in a couple of places.

The "less simple" of the attached patches replaces :clojure.main/trace
(the result of Throwable->map) in the report, however an even more
advanced one would be able to replace ex-data everywhere in
:clojure.main/trace where it can occur.

Being able to narrow down which part of the report caused pprint to
fail is an open problem - I haven't looked much into clojure.pprint
itself.

In the patch drafts, I haven't considered the intricacies of reporting
errors reporting errors - I think a Java stack trace should be enough,
otherwise what if we get another nasty ex-data when reporting an error
reporting an error reporting an error?

I also haven't checked if it's possible to break pprint for things
other than ex-data keys/values - maybe exceptions or even stack frames
themselves? Those cases though should be less common.

I was basing on the master branch Clojure, commit 5451cee0 when
preparing and testing patch drafts.

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clojure.main/report-error contains a call to pprint which may throw, obscuring the real failure