karma-runner/karma

Extract watcher into an injected dependency

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#1468 opened on Jun 24, 2015

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apidiscusshelp wantedtype: feature

Description

I'm writing a plugin that integrates Karma with Broccoli so that it can lean fully on broccoli for all pre-processing, building, etc... The reason being that if you have a Brocfile, then you already have your build toolchain defined in one place, so you might as well utilize it from your test runner. That way, instead of maintaining a parallel build systems: one for your test runner and one for development/production, you can just npm install karma-broccoli and it will know how and when to build, and also which files the build generates. I have the single run use-case working where you invoke karma run. It waits until a build runs (if there is a build), and then executes the test suite.

For the config.autoWatch use-case, I'd like to replace the normal karma watcher with the Broccoli watcher for the same reason I want Broccoli to be responsible for the build, it already knows what to to watch for and consequently, what to build. It would be nice if I could just swap out the broccoli watcher for the bundled karma watcher, but at the moment it is hard coded to the watch function in watcher.js https://github.com/karma-runner/karma/blob/master/lib/server.js#L54

While the dependencies to the watch() function are injected, the watcher itself is not, so I'd like to see if you would be open to extracting the watcher into a first-class injected dependency. If so, I'd be happy to take a stab at implementing it.

Contributor guide

Tech stack
javascript
Domain
testingbackend
Issue type
refactor
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
Node.jsKarma internalsdependency injectionJavaScript
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
Investigate the current watcher implementation in lib/server.js, specifically the watch function. Understand how other dependencies are injected in Karma (e.g., using the di.js library). The goal is to extract the watcher into a separate injectable module so that it can be replaced with a custom watcher (e.g., from Broccoli). Look at the existing code at https://github.com/karma runner/karma/blob/master/lib/server.js#L54 and related files to see the injection pattern. Then propose a change that creates a new injectable service for the watcher and updates the server to use it via dependency injection.