yarnpkg/yarn

Possibility to add warning when running yarn in directory containing node_modules but missing yarn.lock

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#3373 opened on May 10, 2017

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Description

Would it be possible to add some kind of warning when running yarn inside directory where node_modules already exist, but there is no yarn.lock file?

The only use-case for this should be when migrating from npm to yarn. I realized yarn updated all my node_modules only after I ran yarn command and then it was too late to search for yarn import.

It would be nice to get warning, that running yarn or yarn install without yarn.lock will result in node_modules being downloaded and updated.

I realize this experience is depending on environment, but the destructive nature of such simple mistake could warrant some kind of protection against it.

Alternatively, running yarn command in this specific case, could by default fallback to yarn import command instead of yarn install.

Also yarn import command could be mentioned on https://yarnpkg.com/lang/en/docs/migrating-from-npm/ page.

Contributor guide

Tech stack
javascriptnodejs
Domain
clideveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
clear
Prerequisites
familiarity with yarn CLIbasic Node.js development
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75
Research direction
Implement a check in the yarn CLI's install command: if node modules exists but no yarn.lock, print a warning suggesting to run 'yarn import' for migration from npm. Alternatively, automatically fallback to 'yarn import' in that scenario. The relevant code is likely in src/cli/commands/install.js. Also update the migration guide at https://yarnpkg.com/lang/en/docs/migrating from npm/ to mention the warning and yarn import.