avajs/ava

Make watch mode wait for the file system to be idle, and have that be configurable

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#2715 opened on Mar 13, 2021

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enhancementhelp wantedscope:watch-mode

Description

Based on discussion in https://github.com/avajs/ava/discussions/2702, projects with more complicated build setups may want to configure how long watch mode waits for the filesystem to become idle, lest it runs tests prematurely.

~We currently wait at least 100ms, but debounce for another 10ms after changes. ~Instead let's introduce a watchFsIdle option that defaults to 500ms. This should be configurable through config files only, not CLI flags. We should take time strings, like the timeout option.

Other name suggestions welcome.

The watcher should wait the duration of idle time after the last change. If another change is detected, it should again wait the duration of the idle time.

This likely impacts the current watcher tests which are rather brittle. We also have some integration tests that may be affected.

Contributor guide

Tech stack
javascriptnodejs
Domain
toolingtesting
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Familiarity with Node.jsUnderstanding of AVA's watch modeExperience with config file handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue requests a configurable idle time for the watch mode. Start by examining the current watcher implementation in `lib/watcher.js`, particularly the debounce logic. The option should be named `watchFsIdle` and accept time strings like the `timeout` option. It should be configurable only through config files, not CLI. Implement the logic to wait the idle time after the last file change, resetting on new changes. Update the watcher tests in `test tap/watcher.js` and integration tests in `test tap/integration/watcher.js` accordingly. There is a linked discussion (#2702) for context.