karma-runner/karma

[Question] Can you access preprocessor errors programatically?

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#2064 opened on Apr 20, 2016

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 (9 comments) (1 reaction) (0 assignees)JavaScript (11,918 stars) (1,703 forks)batch import
help wantedtype: bug

Description

I'm running karma programatically through the Server API and was wondering if there was a good way catch preprocessor errors when they occur.

Right now, if a preprocessor (babel for example) fails, I'll just see a message logged from Karma, but the server will still start up.

I'd like to be able to cancel the whole process, or at least catch the error when it occurs. I tried tracing my way through the source, and couldn't exactly understand what happens when a preprocessor invokes it's callback with an error: https://github.com/karma-runner/karma/blob/master/lib/preprocessor.js#L26

Any advice?

Contributor guide

Tech stack
javascriptnodejs
Domain
testingdeveloper experience
Issue type
feature
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.
1-3 hours
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.
mostly clear
Prerequisites
Familiarity with Node.jsUnderstanding of Karma's preprocessor systemBasic knowledge of error handling in callbacks
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Examine the Karma source code, especially lib/preprocessor.js (line 26) to understand how preprocessor errors are currently handled. Look at the Server API documentation and see if there are events or hooks to capture errors. Consider proposing a new event or callback modification. Since the issue is from 2016, check if later versions have addressed this. The linked file shows that the done callback is called with an error object; investigate how that error propagates.