anmonteiro/lumo

Improvements to exception messages and printing

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#474 opened on Apr 23, 2019

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help wanted

Description

Lumo v1.10.1.

Steps (based on https://dev.clojure.org/jira/browse/CLJS-2913?focusedCommentId=50751):

Execute in Lumo:

(require '[cljs.spec.alpha :as s])
(require '[cljs.spec.test.alpha :as st])

;; instrumenting a function
(s/fdef foobar :args (s/cat :x int?))
(defn foobar [x] x)

(st/instrument)

;; set up an example spec printer
(set! s/*explain-out* (fn [e-data] (println "SPEC ERROR!")))

(foobar "")

Actual:

Call to #'cljs.user/foobar did not conform to spec.

Expected:

Execution error - invalid arguments to user/foobar at (REPL:1).
SPEC ERROR!

See the related Planck issue https://github.com/planck-repl/planck/issues/845 which in turn follows https://dev.clojure.org/jira/browse/CLJS-2913.

Also this https://github.com/bhb/expound issue seems to be related (as the lib is based on setting s/*explain-out*): https://github.com/bhb/expound/issues/152.

Contributor guide

Tech stack
None
Domain
developer experiencetooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
ClojureScriptcljs.specLumo REPL internals
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine how Lumo prints exception messages. Look at the cljs.repl code that generates the 'did not conform to spec' message. The custom explain out function should be called after the initial error message. May need to modify the instrument function or the error handler. Refer to the Planck issue (https://github.com/planck repl/planck/issues/845) and CLJS 2913 for similar fixes.