jestjs/jest

Expose project matching behaviour

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#11171 opened on Mar 8, 2021

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:rocket: Feature RequestHelp WantedPinned

Description

🚀 Feature Proposal

Expose the logic that determines what project a file belongs to. Given a file path and a Jest configuration, what options apply?

Motivation

To allow third-party tools to understand Jest configurations. E.g: https://github.com/jest-community/eslint-plugin-jest/pull/754#issuecomment-780396777

Example

I am not sure what package this logic currently resides in, but something along the lines of:

import { resolveOptions } from '@jest/options';
import { readConfig } from '@jest/config';

const config = await readConfig('/path/to/jest.config.js');
const options = await resolveOptions('/path/to/unit.test.js', config);

Pitch

The projects logic is very specific to Jest, and recreating it externally would likely be erroneous and fall out-of-date quickly.

Contributor guide

Tech stack
typescriptnodejs
Domain
apitestingdeveloper 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.
1-2 days
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.
needs investigation
Prerequisites
Understanding of Jest's project matchingFamiliarity with Jest's configuration system
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Investigate the current implementation of project matching in Jest, likely in packages like jest config or jest core. The issue references a related PR in eslint plugin jest. Look at the link provided for context on what third party tools need. Determine where the logic resides (e.g., resolveOptions) and plan to export it via a new package like @jest/options. Examine existing config reading code to ensure the API is flexible enough.